From a6012a91345b7a413d7c3f8468faf3d8cd101e7f Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Fri, 18 Aug 2023 17:05:54 +0300
Subject: [PATCH 01/14] t.Parallel for all that's possible

---
 assert/goid_test.go              |  1 +
 internal/debug/debug_test.go     | 15 ++++++++++++---
 internal/handler/handler_test.go | 11 +++++++++--
 internal/str/str_test.go         |  9 ++++-----
 try/out_test.go                  |  2 ++
 5 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/assert/goid_test.go b/assert/goid_test.go
index 451e199..2e53415 100644
--- a/assert/goid_test.go
+++ b/assert/goid_test.go
@@ -5,6 +5,7 @@ import (
 )
 
 func TestGoid(t *testing.T) {
+	t.Parallel()
 	stackBytes := []byte(`goroutine 518 [running]:
 `)
 
diff --git a/internal/debug/debug_test.go b/internal/debug/debug_test.go
index 8d34d0a..638486a 100644
--- a/internal/debug/debug_test.go
+++ b/internal/debug/debug_test.go
@@ -37,6 +37,7 @@ func TestFullName(t *testing.T) {
 }
 
 func TestIsAnchor(t *testing.T) {
+	t.Parallel()
 	type args struct {
 		input string
 		StackInfo
@@ -78,8 +79,10 @@ func TestIsAnchor(t *testing.T) {
 			"github.com/lainio/err2/try.To1[...](...)",
 			StackInfo{"lainio/err2", "", 0, nil, nil}}, true},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			test.Require(t, tt.retval == tt.isAnchor(tt.input), "equal")
 		})
 	}
@@ -132,6 +135,7 @@ func TestIsFuncAnchor(t *testing.T) {
 }
 
 func TestFnLNro(t *testing.T) {
+	t.Parallel()
 	tests := []struct {
 		name   string
 		input  string
@@ -141,8 +145,10 @@ func TestFnLNro(t *testing.T) {
 			"	/Users/harrilainio/go/pkg/mod/github.com/lainio/err2@v0.8.5/internal/handler/handler.go:69 +0xbc",
 			69},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			output := fnLNro(tt.input)
 			test.Require(t, output == tt.output, output)
 		})
@@ -210,6 +216,7 @@ func TestStackPrint_noLimits(t *testing.T) {
 }
 
 func TestStackPrintForTest(t *testing.T) {
+	t.Parallel()
 	tests := []struct {
 		name   string
 		input  string
@@ -220,8 +227,10 @@ func TestStackPrintForTest(t *testing.T) {
 		{"short", input, outputForTestLvl2, 2},
 		//{"real test trace", inputFromTest, outputFromTest, 4},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			r := strings.NewReader(tt.input)
 			w := new(bytes.Buffer)
 			printStackForTest(r, w, tt.lvl)
diff --git a/internal/handler/handler_test.go b/internal/handler/handler_test.go
index d748c5f..62f1983 100644
--- a/internal/handler/handler_test.go
+++ b/internal/handler/handler_test.go
@@ -12,6 +12,7 @@ import (
 )
 
 func TestProcess(t *testing.T) {
+	t.Parallel()
 	type args struct {
 		handler.Info
 	}
@@ -113,8 +114,10 @@ func TestProcess(t *testing.T) {
 				errStr:      "error",
 			}},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			if handler.WorkToDo(tt.args.Any, tt.args.Err) {
 				handler.Process(&tt.args.Info)
 
@@ -142,6 +145,7 @@ func Handle() {
 }
 
 func TestPreProcess_debug(t *testing.T) {
+	t.Parallel()
 	// in real case PreProcess is called from Handle function. So, we make our
 	// own Handle here. Now our test function name will be the Handle caller
 	// and that's what error stack tracing is all about
@@ -159,6 +163,7 @@ func TestPreProcess_debug(t *testing.T) {
 }
 
 func TestPreProcess(t *testing.T) {
+	t.Parallel()
 	type args struct {
 		handler.Info
 		a []any
@@ -225,8 +230,10 @@ func TestPreProcess(t *testing.T) {
 				errStr:    "",
 			}},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			if handler.WorkToDo(tt.args.Any, tt.args.Err) &&
 				len(tt.args.a) > 0 {
 
diff --git a/internal/str/str_test.go b/internal/str/str_test.go
index f9e0b77..dbb13c6 100644
--- a/internal/str/str_test.go
+++ b/internal/str/str_test.go
@@ -46,13 +46,12 @@ func TestDecamel(t *testing.T) {
 		{"unnatural method and anonym", args{"(**DIDAgent)...AssertWallet...Func1"}, "didagent assert wallet: func1"},
 		{"from spf13 cobra", args{"bot.glob..func5"}, "bot: glob: func5"},
 	}
-	for _, tt := range tests {
-		s := tt.args.s
-		want := tt.want
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()
-			got := str.Decamel(s)
-			test.RequireEqual(t, got, want)
+			got := str.Decamel(tt.args.s)
+			test.RequireEqual(t, got, tt.want)
 		})
 	}
 }
diff --git a/try/out_test.go b/try/out_test.go
index 000daff..d032771 100644
--- a/try/out_test.go
+++ b/try/out_test.go
@@ -90,6 +90,7 @@ func ExampleResult1_Logf() {
 }
 
 func TestResult2_Logf(t *testing.T) {
+	t.Parallel()
 	// Set log tracing to stdout that we can see it in Example output. In
 	// normal cases that would be a Logging stream or stderr.
 	err2.SetLogTracer(os.Stdout)
@@ -110,6 +111,7 @@ func TestResult2_Logf(t *testing.T) {
 }
 
 func TestResult_Handle(t *testing.T) {
+	t.Parallel()
 	// try out f() |err| handle to show how to stop propagate error
 	callFn := func(mode int) (err error) {
 		defer err2.Handle(&err)

From a4478e4583b69d76e84e348f1e7e7a4924e429fd Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Fri, 18 Aug 2023 17:07:06 +0300
Subject: [PATCH 02/14] tests for issue-18 & t.Parallel for rest

---
 err2_test.go | 205 ++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 186 insertions(+), 19 deletions(-)

diff --git a/err2_test.go b/err2_test.go
index 18caecb..b893172 100644
--- a/err2_test.go
+++ b/err2_test.go
@@ -24,7 +24,8 @@ func noErr() error {
 	return nil
 }
 
-func TestTry_noError(_ *testing.T) {
+func TestTry_noError(t *testing.T) {
+	t.Parallel()
 	try.To1(noThrow())
 	try.To2(twoStrNoThrow())
 	try.To2(intStrNoThrow())
@@ -32,6 +33,7 @@ func TestTry_noError(_ *testing.T) {
 }
 
 func TestDefault_Error(t *testing.T) {
+	t.Parallel()
 	var err error
 	defer err2.Handle(&err)
 
@@ -41,6 +43,7 @@ func TestDefault_Error(t *testing.T) {
 }
 
 func TestTry_Error(t *testing.T) {
+	t.Parallel()
 	var err error
 	defer err2.Handle(&err, func(err error) error { return err })
 
@@ -49,27 +52,176 @@ func TestTry_Error(t *testing.T) {
 	t.Fail() // If everything works we are never here
 }
 
-func TestHandle_NoError(t *testing.T) {
-	var err error
-	var handlerCalled bool
-	defer func() {
-		test.Require(t, handlerCalled)
-	}()
-	defer err2.Handle(&err, func(err error) error {
-		// this should not be called, so lets try to fuckup things...
-		handlerCalled = false
-		return err
+func TestHandle_noerrHandler(t *testing.T) {
+	t.Parallel()
+	t.Run("noerr handler in ONLY one and NO error happens", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var handlerCalled bool
+		defer func() {
+			test.Require(t, handlerCalled)
+		}()
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			handlerCalled = noerr
+		})
+
+		try.To(noErr())
+	})
+
+	t.Run("noerr handler is the last and NO error happens", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var handlerCalled bool
+		defer func() {
+			test.Require(t, handlerCalled)
+		}()
+		defer err2.Handle(&err, func(err error) error {
+			// this should not be called, so lets try to fuckup things...
+			handlerCalled = false
+			test.Require(t, false)
+			return err
+		})
+
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			handlerCalled = noerr
+		})
+
+		try.To(noErr())
+	})
+
+	t.Run("noerr handler is the last and error happens", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var handlerCalled bool
+		defer func() {
+			test.Require(t, !handlerCalled)
+		}()
+		defer err2.Handle(&err, func(err error) error {
+			handlerCalled = false
+			test.Require(t, true, "error should be handled")
+			return err
+		})
+
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			test.Require(t, noerr)
+			handlerCalled = noerr
+		})
+
+		try.To1(throw())
 	})
 
-	// This is the handler we are thesting!
-	defer err2.Handle(&err, func(noerr bool) {
-		handlerCalled = noerr
+	t.Run("noerr is error order is first and error happens", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var handlerCalled bool
+		defer func() {
+			test.Require(t, !handlerCalled)
+		}()
+
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			test.Require(t, false, "if error occurs/reset, this cannot happen")
+			handlerCalled = noerr
+		})
+
+		defer err2.Handle(&err, func(err error) error {
+			// this should not be called, so lets try to fuckup things...
+			handlerCalled = false
+			test.Require(t, err != nil)
+			return err
+		})
+		try.To1(throw())
 	})
 
-	try.To(noErr())
+	t.Run("noerr handler is first and NO error happens", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var handlerCalled bool
+		defer func() {
+			test.Require(t, handlerCalled)
+		}()
+
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			test.Require(t, noerr)
+			handlerCalled = noerr
+		})
+
+		defer err2.Handle(&err, func(err error) error {
+			test.Require(t, false, "no error to handle!")
+			// this should not be called, so lets try to fuckup things...
+			handlerCalled = false // see first deferred function
+			return err
+		})
+		try.To(noErr())
+	})
+
+	t.Run("noerr handler is first of MANY and NO error happens", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var handlerCalled bool
+		defer func() {
+			test.Require(t, handlerCalled)
+		}()
+
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			test.Require(t, noerr)
+			handlerCalled = noerr
+		})
+
+		defer err2.Handle(&err, func(err error) error {
+			test.Require(t, false, "no error to handle!")
+			// this should not be called, so lets try to fuckup things...
+			handlerCalled = false // see first deferred function
+			return err
+		})
+
+		defer err2.Handle(&err, func(err error) error {
+			test.Require(t, false, "no error to handle!")
+			// this should not be called, so lets try to fuckup things...
+			handlerCalled = false // see first deferred function
+			return err
+		})
+		try.To(noErr())
+	})
+
+	t.Run("noerr handler is middle of MANY and NO error happens", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var handlerCalled bool
+		defer func() {
+			test.Require(t, handlerCalled)
+		}()
+
+		defer err2.Handle(&err, func(err error) error {
+			test.Require(t, false, "no error to handle!")
+			// this should not be called, so lets try to fuckup things...
+			handlerCalled = false // see first deferred function
+			return err
+		})
+
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			test.Require(t, noerr)
+			handlerCalled = noerr
+		})
+
+		defer err2.Handle(&err, func(err error) error {
+			test.Require(t, false, "no error to handle!")
+			// this should not be called, so lets try to fuckup things...
+			handlerCalled = false // see first deferred function
+			return err
+		})
+		try.To(noErr())
+	})
 }
 
 func TestPanickingCatchAll(t *testing.T) {
+	t.Parallel()
 	type args struct {
 		f func()
 	}
@@ -124,8 +276,10 @@ func TestPanickingCatchAll(t *testing.T) {
 			nil,
 		},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			defer func() {
 				test.Require(t, recover() == nil, "panics should NOT carry on")
 			}()
@@ -135,6 +289,7 @@ func TestPanickingCatchAll(t *testing.T) {
 }
 
 func TestPanickingCarryOn_Handle(t *testing.T) {
+	t.Parallel()
 	type args struct {
 		f func()
 	}
@@ -165,8 +320,10 @@ func TestPanickingCarryOn_Handle(t *testing.T) {
 			nil,
 		},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			defer func() {
 				test.Require(t, recover() != nil, "panics should went thru when not our errors")
 			}()
@@ -176,6 +333,7 @@ func TestPanickingCarryOn_Handle(t *testing.T) {
 }
 
 func TestPanicking_Handle(t *testing.T) {
+	t.Parallel()
 	type args struct {
 		f func() (err error)
 	}
@@ -286,8 +444,10 @@ func TestPanicking_Handle(t *testing.T) {
 			myErr,
 		},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			defer func() {
 				r := recover()
 				if tt.wants == nil {
@@ -303,6 +463,7 @@ func TestPanicking_Handle(t *testing.T) {
 }
 
 func TestPanicking_Catch(t *testing.T) {
+	t.Parallel()
 	type args struct {
 		f func()
 	}
@@ -331,8 +492,10 @@ func TestPanicking_Catch(t *testing.T) {
 			nil,
 		},
 	}
-	for _, tt := range tests {
+	for _, ttv := range tests {
+		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
 			defer func() {
 				test.Require(t, recover() == nil, "panics should NOT carry on")
 			}()
@@ -342,6 +505,7 @@ func TestPanicking_Catch(t *testing.T) {
 }
 
 func TestCatch_Error(t *testing.T) {
+	t.Parallel()
 	defer err2.Catch()
 
 	try.To1(throw())
@@ -350,6 +514,7 @@ func TestCatch_Error(t *testing.T) {
 }
 
 func Test_TryOutError(t *testing.T) {
+	t.Parallel()
 	defer err2.Catch(func(err error) error {
 		test.RequireEqual(t, err.Error(), "fails: test: this is an ERROR",
 			"=> we should catch right error str here")
@@ -368,6 +533,7 @@ func Test_TryOutError(t *testing.T) {
 }
 
 func TestCatch_Panic(t *testing.T) {
+	t.Parallel()
 	panicHandled := false
 	defer func() {
 		// when err2.Catch's panic handler works fine, panic is handled
@@ -390,6 +556,7 @@ func TestCatch_Panic(t *testing.T) {
 }
 
 func TestSetErrorTracer(t *testing.T) {
+	t.Parallel()
 	w := err2.ErrorTracer()
 	test.Require(t, w == nil, "error tracer should be nil")
 	var w1 io.Writer

From a44fce96cc28d8b4b93e34766506974a5ca11685 Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Fri, 18 Aug 2023 17:07:52 +0300
Subject: [PATCH 03/14] issue-18 bug fix: err wasn't checked, but now is

---
 internal/handler/handler.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal/handler/handler.go b/internal/handler/handler.go
index ce7583b..e6d29e4 100644
--- a/internal/handler/handler.go
+++ b/internal/handler/handler.go
@@ -67,7 +67,7 @@ func NilNoop(err error) error { return err }
 // func ErrorNoop(err error) {}
 
 func (i *Info) callNilHandler() {
-	if i.CheckHandler != nil {
+	if i.CheckHandler != nil && i.safeErr() == nil {
 		i.CheckHandler(true)
 		// there is no err and user wants to handle OK with our pkg:
 		// nothing more to do here after callNilHandler call

From 8589b10df1f99d526a499e0733531342cea1af2c Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Fri, 18 Aug 2023 17:39:38 +0300
Subject: [PATCH 04/14] handler_test uses pkg vars, cannot t.Parallel

---
 internal/handler/handler_test.go | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/internal/handler/handler_test.go b/internal/handler/handler_test.go
index 62f1983..027e9d7 100644
--- a/internal/handler/handler_test.go
+++ b/internal/handler/handler_test.go
@@ -12,7 +12,7 @@ import (
 )
 
 func TestProcess(t *testing.T) {
-	t.Parallel()
+	// NOTE. No Parallel, uses pkg lvl variables
 	type args struct {
 		handler.Info
 	}
@@ -117,7 +117,7 @@ func TestProcess(t *testing.T) {
 	for _, ttv := range tests {
 		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
+			// NOTE. No Parallel, uses pkg lvl variables
 			if handler.WorkToDo(tt.args.Any, tt.args.Err) {
 				handler.Process(&tt.args.Info)
 
@@ -145,7 +145,8 @@ func Handle() {
 }
 
 func TestPreProcess_debug(t *testing.T) {
-	t.Parallel()
+	// NOTE. No Parallel, uses pkg lvl variables
+
 	// in real case PreProcess is called from Handle function. So, we make our
 	// own Handle here. Now our test function name will be the Handle caller
 	// and that's what error stack tracing is all about
@@ -163,7 +164,7 @@ func TestPreProcess_debug(t *testing.T) {
 }
 
 func TestPreProcess(t *testing.T) {
-	t.Parallel()
+	// NOTE. No Parallel, uses pkg lvl variables
 	type args struct {
 		handler.Info
 		a []any
@@ -233,7 +234,7 @@ func TestPreProcess(t *testing.T) {
 	for _, ttv := range tests {
 		tt := ttv
 		t.Run(tt.name, func(t *testing.T) {
-			t.Parallel()
+			// NOTE. No Parallel, uses pkg lvl variables
 			if handler.WorkToDo(tt.args.Any, tt.args.Err) &&
 				len(tt.args.a) > 0 {
 

From 3398b4962abfe1f18c1983af42a6d97ee5ce08ef Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Fri, 18 Aug 2023 18:12:27 +0300
Subject: [PATCH 05/14] version info 0.9.41 to README

---
 README.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/README.md b/README.md
index 0678ae9..14457c3 100644
--- a/README.md
+++ b/README.md
@@ -430,6 +430,10 @@ Please see the full version history from [CHANGELOG](./CHANGELOG.md).
 
 ### Latest Release
 
+##### 0.9.41
+- Issue #18: **bug fixed**: noerr-handler had to be the last one of the err2
+  handlers
+
 ##### 0.9.40
 - Significant performance boost for: `defer err2.Handle/Catch()` 
   - **3x faster happy path than the previous version, which is now equal to

From a1e64a4912a89501a86499b171d58dbc060a21ba Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Fri, 18 Aug 2023 18:33:12 +0300
Subject: [PATCH 06/14] godoc typos & better example with multi-error

---
 err2.go | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/err2.go b/err2.go
index d5ed484..c9cf1db 100644
--- a/err2.go
+++ b/err2.go
@@ -63,7 +63,9 @@ var (
 // an second argument:
 //
 //	defer err2.Handle(&err, func(err error) error {
-//		os.Remove(dst)
+//		if rmErr := os.Remove(dst); rmErr != nil {
+//			return fmt.Errorf("%w: cleanup error: %w", err, rmErr)
+//		}
 //		return err
 //	})
 //
@@ -71,8 +73,8 @@ var (
 // panic handler function:
 //
 //	defer err2.Handle(&err,
-//	   err2.Err( func(error) { os.Remove(dst) }), // err2.Err keeps it short
-//	   func(p any) {} // panic handler, it's stops panics, you can re-throw
+//	   err2.Err( func(error) { os.Remove(dst) }), // err2.Err() keeps it short
+//	   func(p any) {} // <- handler stops panics, re-throw or not
 //	)
 func Handle(err *error, a ...any) {
 	// This and others are similar but we need to call `recover` here because

From 049027fbc3b63cc888e399427149e9a2f073a835 Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Sat, 19 Aug 2023 10:15:06 +0300
Subject: [PATCH 07/14] asserter methods deprecated

---
 assert/asserter.go | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/assert/asserter.go b/assert/asserter.go
index ddc10b8..5974e0f 100644
--- a/assert/asserter.go
+++ b/assert/asserter.go
@@ -48,6 +48,7 @@ const (
 const officialTestOutputPrefix = "    "
 
 // NoImplementation always fails with no implementation.
+// Deprecated: use e.g. assert.NotImplemented(), only default asserter is used.
 func (asserter Asserter) NoImplementation(a ...any) {
 	asserter.reportAssertionFault("not implemented", a...)
 }
@@ -55,6 +56,7 @@ func (asserter Asserter) NoImplementation(a ...any) {
 // True asserts that term is true. If not it panics with the given formatting
 // string. Note! This and Truef are the most performant of all the assertion
 // functions.
+// Deprecated: use e.g. assert.That(), only default asserter is used.
 func (asserter Asserter) True(term bool, a ...any) {
 	if !term {
 		asserter.reportAssertionFault("assertion fault", a...)
@@ -63,6 +65,7 @@ func (asserter Asserter) True(term bool, a ...any) {
 
 // Truef asserts that term is true. If not it panics with the given formatting
 // string.
+// Deprecated: use e.g. assert.That(), only default asserter is used.
 func (asserter Asserter) Truef(term bool, format string, a ...any) {
 	if !term {
 		if asserter.hasStackTrace() {
@@ -76,6 +79,7 @@ func (asserter Asserter) Truef(term bool, format string, a ...any) {
 // panics/errors (current Asserter) with the given msg. Note! This is very slow
 // (before we have generics). If you need performance use EqualInt. It's not so
 // convenient, though.
+// Deprecated: use e.g. assert.Len(), only default asserter is used.
 func (asserter Asserter) Len(obj any, length int, a ...any) {
 	ok, l := getLen(obj)
 	if !ok {
@@ -90,6 +94,7 @@ func (asserter Asserter) Len(obj any, length int, a ...any) {
 
 // EqualInt asserts that integers are equal. If not it panics/errors (current
 // Asserter) with the given msg.
+// Deprecated: use e.g. assert.Equal(), only default asserter is used.
 func (asserter Asserter) EqualInt(val, want int, a ...any) {
 	if want != val {
 		defMsg := fmt.Sprintf("got %d, want %d", val, want)
@@ -101,6 +106,7 @@ func (asserter Asserter) EqualInt(val, want int, a ...any) {
 // panics/errors (current Asserter) with the given msg. Note! This is very slow
 // (before we have generics). If you need performance use EqualInt. It's not so
 // convenient, though.
+// Deprecated: use e.g. assert.Len(), only default asserter is used.
 func (asserter Asserter) Lenf(obj any, length int, format string, a ...any) {
 	args := combineArgs(format, a)
 	asserter.Len(obj, length, args...)
@@ -108,6 +114,7 @@ func (asserter Asserter) Lenf(obj any, length int, format string, a ...any) {
 
 // Empty asserts that length of the object is zero. If not it panics with the
 // given formatting string. Note! This is slow.
+// Deprecated: use e.g. assert.Empty(), only default asserter is used.
 func (asserter Asserter) Empty(obj any, msg ...any) {
 	ok, l := getLen(obj)
 	if !ok {
@@ -122,6 +129,7 @@ func (asserter Asserter) Empty(obj any, msg ...any) {
 
 // NotEmptyf asserts that length of the object greater than zero. If not it
 // panics with the given formatting string. Note! This is slow.
+// Deprecated: use e.g. assert.NotEmpty(), only default asserter is used.
 func (asserter Asserter) NotEmptyf(obj any, format string, msg ...any) {
 	args := combineArgs(format, msg)
 	asserter.Empty(obj, args...)
@@ -129,6 +137,7 @@ func (asserter Asserter) NotEmptyf(obj any, format string, msg ...any) {
 
 // NotEmpty asserts that length of the object greater than zero. If not it
 // panics with the given formatting string. Note! This is slow.
+// Deprecated: use e.g. assert.NotEmpty(), only default asserter is used.
 func (asserter Asserter) NotEmpty(obj any, msg ...any) {
 	ok, l := getLen(obj)
 	if !ok {

From c432749e053f2144e7079ca029ba2002804ada1d Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Sat, 19 Aug 2023 10:15:53 +0300
Subject: [PATCH 08/14] assert pkg documentation for asserters

---
 assert/assert.go | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/assert/assert.go b/assert/assert.go
index 7f376aa..58772d8 100644
--- a/assert/assert.go
+++ b/assert/assert.go
@@ -16,34 +16,45 @@ import (
 type defInd = uint32
 
 const (
-	// Production is the best asserter for most uses. The assertion violations
-	// are treated as Go error values. And only a pragmatic caller info is
-	// automatically included into the error message like file name, line
-	// number, and caller function.
+	// Production (pkg default) is the best asserter for most uses. The
+	// assertion violations are treated as Go error values. And only a
+	// pragmatic caller info is automatically included into the error message
+	// like file name, line number, and caller function, all in one line:
+	//
+	//  copy file: main.go:37: CopyFile(): assertion violation: string shouldn't be empty
 	Production defInd = 0 + iota
 
 	// Development is the best asserter for most development uses. The
 	// assertion violations are treated as Go error values. And a formatted
 	// caller info is automatically included to the error message like file
-	// name, line number, and caller function.
+	// name, line number, and caller function. Everything in a beautiful
+	// multi-line message:
+	//
+	//  --------------------------------
+	//  Assertion Fault at:
+	//  main.go:37 CopyFile():
+	//  assertion violation: string shouldn't be empty
+	//  --------------------------------
 	Development
 
 	// Test minimalistic asserter for unit test use. More pragmatic is the
-	// TestFull asserter (default).
+	// TestFull asserter (test default).
 	//
-	// Use this asserter if your IDE/editor doesn't support long file names, or
-	// for temporary problem solving for your programming environment.
+	// Use this asserter if your IDE/editor doesn't support full file names and
+	// it relies a relative path (Go standard). You can use this also if you
+	// need temporary problem solving for your programming environment.
 	Test
 
-	// TestFull asserter (default). The TestFull asserter includes caller info
-	// and call stack for unit testing, similarly like err2's error traces.
+	// TestFull asserter (test default). The TestFull asserter includes the
+	// caller info and the call stack for unit testing, similarly like err2's
+	// error traces.
 	//
 	// The call stack produced by the test asserts can be used over Go module
 	// boundaries. For example, if your app and it's sub packages both use
 	// err2/assert for unit testing and runtime checks, the runtime assertions
-	// will be automatically converted to test asserts on the fly. If any of
-	// the runtime asserts in sub packages fails during the app tests, the
-	// current app test fails too.
+	// will be automatically converted to test asserts. If any of the runtime
+	// asserts of the sub packages fails during the app tests, the app test
+	// fails as well.
 	//
 	// Note, that the cross-module assertions produce long file names (path
 	// included), and some of the Go test result parsers cannot handle that.
@@ -53,7 +64,7 @@ const (
 	TestFull
 
 	// Debug asserter transforms assertion violations to panics which is the
-	// patter that e.g. Go's standard library uses:
+	// pattern that e.g. Go's standard library uses:
 	//
 	//   if p == nil {
 	//        panic("pkg: ptr cannot be nil")

From 56256a77217d4d8a4244c415bbac70887291d9b0 Mon Sep 17 00:00:00 2001
From: lainio <harri.lainio@iki.fi>
Date: Sun, 20 Aug 2023 14:09:26 +0300
Subject: [PATCH 09/14] more norrr test cases

---
 err2_test.go | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/err2_test.go b/err2_test.go
index b893172..0463d38 100644
--- a/err2_test.go
+++ b/err2_test.go
@@ -113,7 +113,7 @@ func TestHandle_noerrHandler(t *testing.T) {
 		try.To1(throw())
 	})
 
-	t.Run("noerr is error order is first and error happens", func(t *testing.T) {
+	t.Run("noerr is first and error happens", func(t *testing.T) {
 		t.Parallel()
 		var err error
 		var handlerCalled bool
@@ -173,6 +173,8 @@ func TestHandle_noerrHandler(t *testing.T) {
 			handlerCalled = noerr
 		})
 
+		defer err2.Handle(&err)
+
 		defer err2.Handle(&err, func(err error) error {
 			test.Require(t, false, "no error to handle!")
 			// this should not be called, so lets try to fuckup things...
@@ -189,6 +191,44 @@ func TestHandle_noerrHandler(t *testing.T) {
 		try.To(noErr())
 	})
 
+	t.Run("noerr handler is first of MANY and error happens UNTIL reset", func(t *testing.T) {
+		t.Parallel()
+		var err error
+		var noerrHandlerCalled, errHandlerCalled bool
+		defer func() {
+			test.Require(t, noerrHandlerCalled)
+			test.Require(t, errHandlerCalled)
+		}()
+
+		// This is the handler we are thesting!
+		defer err2.Handle(&err, func(noerr bool) {
+			test.Require(t, true)
+			test.Require(t, noerr)
+			noerrHandlerCalled = noerr
+		})
+
+		// this is the err handler that resets the error to nil
+		defer err2.Handle(&err, func(err error) error {
+			test.Require(t, true) // helps fast debugging
+
+			// this should not be called, so lets try to fuckup things...
+			noerrHandlerCalled = false // see first deferred function
+			// keep the track that we have been here
+			errHandlerCalled = true // see first deferred function
+			return nil
+		})
+
+		defer err2.Handle(&err, func(err error) error {
+			test.Require(t, true) // helps fast debugging
+			// this should not be called, so lets try to fuckup things...
+			noerrHandlerCalled = false // see first deferred function
+
+			errHandlerCalled = true // see first deferred function
+			return err
+		})
+		try.To1(throw())
+	})
+
 	t.Run("noerr handler is middle of MANY and NO error happens", func(t *testing.T) {
 		t.Parallel()
 		var err error
@@ -197,6 +237,8 @@ func TestHandle_noerrHandler(t *testing.T) {
 			test.Require(t, handlerCalled)
 		}()
 
+		defer err2.Handle(&err)
+
 		defer err2.Handle(&err, func(err error) error {
 			test.Require(t, false, "no error to handle!")
 			// this should not be called, so lets try to fuckup things...

From b756914e667de88b02b198364b25137ba9f440f9 Mon Sep 17 00:00:00 2001
From: lainio <harri.lainio@iki.fi>
Date: Sun, 20 Aug 2023 14:10:02 +0300
Subject: [PATCH 10/14] more go doc to try.ToX functions

---
 try/try.go | 48 ++++++++++++++++++++++++++++++++++++------------
 1 file changed, 36 insertions(+), 12 deletions(-)

diff --git a/try/try.go b/try/try.go
index f7c10c8..f476ae9 100644
--- a/try/try.go
+++ b/try/try.go
@@ -67,34 +67,58 @@ import (
 	"github.com/lainio/err2"
 )
 
-// To is a helper function to call functions which returns (error)
-// and check the error value. If an error occurs, it panics the error where err2
-// handlers can catch it if needed.
+// To is a helper function to call functions which returns an error value and
+// check the value. If an error occurs, it panics the error so that err2
+// handlers can catch it if needed. Note! If no err2.Handle or err2.Catch exist
+// in the call stack and To detects the error, the error is not handled, and the
+// app will crash. When using try.To functions you should always have proper
+// err2.Handle or err2.Catch statements in the call stack.
+//
+//	defer err2.Handle(&err)
+//	...
+//	try.To(w.Close())
 func To(err error) {
 	if err != nil {
 		panic(err)
 	}
 }
 
-// To1 is a helper function to call functions which returns (T, error)
-// and check the error value. If an error occurs, it panics the error where err2
-// handlers can catch it if needed.
+// To1 is a helper function to call functions which returns values (T, error)
+// and check the error value. If an error occurs, it panics the error so that
+// err2 handlers can catch it if needed. Note! If no err2.Handle or err2.Catch
+// exist in the call stack and To1 detects the error, the error is not handled,
+// and the app will crash. When using try.To1 functions you should always have
+// proper err2.Handle or err2.Catch statements in the call stack.
+//
+//	defer err2.Handle(&err)
+//	...
+//	r := try.To1(os.Open(src))
 func To1[T any](v T, err error) T {
 	To(err)
 	return v
 }
 
-// To2 is a helper function to call functions which returns (T, U, error)
-// and check the error value. If an error occurs, it panics the error where err2
-// handlers can catch it if needed.
+// To2 is a helper function to call functions which returns values (T, U, error)
+// and check the error value. If an error occurs, it panics the error so that
+// err2 handlers can catch it if needed. Note! If no err2.Handle or err2.Catch
+// exist in the call stack and To2 detects the error, the error is not handled,
+// and the app will crash. When using try.To2 functions you should always have
+// proper err2.Handle or err2.Catch statements in the call stack.
+//
+//	defer err2.Handle(&err)
+//	...
+//	kid, pk := try.To2(keys.CreateAndExportPubKeyBytes(kms.ED25519))
 func To2[T, U any](v1 T, v2 U, err error) (T, U) {
 	To(err)
 	return v1, v2
 }
 
-// To3 is a helper function to call functions which returns (T, U, V, error)
-// and check the error value. If an error occurs, it panics the error where err2
-// handlers can catch it if needed.
+// To3 is a helper function to call functions which returns values (T, U, V,
+// error) and check the error value. If an error occurs, it panics the error so
+// that err2 handlers can catch it if needed. Note! If no err2.Handle or
+// err2.Catch exist in the call stack and To3 detects the error, the error is
+// not handled, and the app will crash. When using try.To3 functions you should
+// always have proper err2.Handle or err2.Catch statements in the call stack.
 func To3[T, U, V any](v1 T, v2 U, v3 V, err error) (T, U, V) {
 	To(err)
 	return v1, v2, v3

From 9cf5db4f6e8d7b8b282ce3ada3427ddd4d84828c Mon Sep 17 00:00:00 2001
From: lainio <harri.lainio@iki.fi>
Date: Sun, 20 Aug 2023 16:27:10 +0300
Subject: [PATCH 11/14] english in try.To docs

---
 try/try.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/try/try.go b/try/try.go
index f476ae9..07e5137 100644
--- a/try/try.go
+++ b/try/try.go
@@ -70,7 +70,7 @@ import (
 // To is a helper function to call functions which returns an error value and
 // check the value. If an error occurs, it panics the error so that err2
 // handlers can catch it if needed. Note! If no err2.Handle or err2.Catch exist
-// in the call stack and To detects the error, the error is not handled, and the
+// in the call stack and To panics an error, the error is not handled, and the
 // app will crash. When using try.To functions you should always have proper
 // err2.Handle or err2.Catch statements in the call stack.
 //
@@ -86,7 +86,7 @@ func To(err error) {
 // To1 is a helper function to call functions which returns values (T, error)
 // and check the error value. If an error occurs, it panics the error so that
 // err2 handlers can catch it if needed. Note! If no err2.Handle or err2.Catch
-// exist in the call stack and To1 detects the error, the error is not handled,
+// exist in the call stack and To1 panics an error, the error is not handled,
 // and the app will crash. When using try.To1 functions you should always have
 // proper err2.Handle or err2.Catch statements in the call stack.
 //
@@ -101,7 +101,7 @@ func To1[T any](v T, err error) T {
 // To2 is a helper function to call functions which returns values (T, U, error)
 // and check the error value. If an error occurs, it panics the error so that
 // err2 handlers can catch it if needed. Note! If no err2.Handle or err2.Catch
-// exist in the call stack and To2 detects the error, the error is not handled,
+// exist in the call stack and To2 panics an error, the error is not handled,
 // and the app will crash. When using try.To2 functions you should always have
 // proper err2.Handle or err2.Catch statements in the call stack.
 //
@@ -116,7 +116,7 @@ func To2[T, U any](v1 T, v2 U, err error) (T, U) {
 // To3 is a helper function to call functions which returns values (T, U, V,
 // error) and check the error value. If an error occurs, it panics the error so
 // that err2 handlers can catch it if needed. Note! If no err2.Handle or
-// err2.Catch exist in the call stack and To3 detects the error, the error is
+// err2.Catch exist in the call stack and To3 panics an error, the error is
 // not handled, and the app will crash. When using try.To3 functions you should
 // always have proper err2.Handle or err2.Catch statements in the call stack.
 func To3[T, U, V any](v1 T, v2 U, v3 V, err error) (T, U, V) {

From c1538a08a55160c2dd1608b9ca1672c7cbf2e74c Mon Sep 17 00:00:00 2001
From: lainio <harri.lainio@iki.fi>
Date: Sun, 20 Aug 2023 17:55:45 +0300
Subject: [PATCH 12/14] better tests for noerr case and chaingin handlers

---
 err2_test.go | 34 ++++++++++++++++++++++++----------
 1 file changed, 24 insertions(+), 10 deletions(-)

diff --git a/err2_test.go b/err2_test.go
index 0463d38..b1540da 100644
--- a/err2_test.go
+++ b/err2_test.go
@@ -11,8 +11,10 @@ import (
 	"github.com/lainio/err2/try"
 )
 
+const errStringInThrow = "this is an ERROR"
+
 func throw() (string, error) {
-	return "", fmt.Errorf("this is an ERROR")
+	return "", fmt.Errorf(errStringInThrow)
 }
 
 func twoStrNoThrow() (string, string, error)        { return "test", "test", nil }
@@ -113,12 +115,16 @@ func TestHandle_noerrHandler(t *testing.T) {
 		try.To1(throw())
 	})
 
-	t.Run("noerr is first and error happens", func(t *testing.T) {
+	t.Run("noerr is first and error happens with many handlers", func(t *testing.T) {
 		t.Parallel()
-		var err error
-		var handlerCalled bool
+		var (
+			err               error
+			finalAnnotatedErr = fmt.Errorf("err: %v", errStringInThrow)
+			handlerCalled     bool
+		)
 		defer func() {
 			test.Require(t, !handlerCalled)
+			test.RequireEqual(t, err.Error(), finalAnnotatedErr.Error())
 		}()
 
 		// This is the handler we are thesting!
@@ -127,11 +133,18 @@ func TestHandle_noerrHandler(t *testing.T) {
 			handlerCalled = noerr
 		})
 
+		// important! test that our handler doesn't change the current error
+		// and it's not nil
+		defer err2.Handle(&err, func(er error) error {
+			test.Require(t, er != nil, "er val: ", er, err)
+			return er
+		})
+
 		defer err2.Handle(&err, func(err error) error {
 			// this should not be called, so lets try to fuckup things...
 			handlerCalled = false
 			test.Require(t, err != nil)
-			return err
+			return finalAnnotatedErr
 		})
 		try.To1(throw())
 	})
@@ -191,7 +204,7 @@ func TestHandle_noerrHandler(t *testing.T) {
 		try.To(noErr())
 	})
 
-	t.Run("noerr handler is first of MANY and error happens UNTIL reset", func(t *testing.T) {
+	t.Run("noerr handler is first of MANY and error happens UNTIL RESET", func(t *testing.T) {
 		t.Parallel()
 		var err error
 		var noerrHandlerCalled, errHandlerCalled bool
@@ -202,14 +215,14 @@ func TestHandle_noerrHandler(t *testing.T) {
 
 		// This is the handler we are thesting!
 		defer err2.Handle(&err, func(noerr bool) {
-			test.Require(t, true)
+			test.Require(t, true) // we are here, for debugging
 			test.Require(t, noerr)
 			noerrHandlerCalled = noerr
 		})
 
-		// this is the err handler that resets the error to nil
+		// this is the err handler that -- RESETS -- the error to nil
 		defer err2.Handle(&err, func(err error) error {
-			test.Require(t, true) // helps fast debugging
+			test.Require(t, err != nil) // helps fast debugging
 
 			// this should not be called, so lets try to fuckup things...
 			noerrHandlerCalled = false // see first deferred function
@@ -219,7 +232,7 @@ func TestHandle_noerrHandler(t *testing.T) {
 		})
 
 		defer err2.Handle(&err, func(err error) error {
-			test.Require(t, true) // helps fast debugging
+			test.Require(t, err != nil) // helps fast debugging
 			// this should not be called, so lets try to fuckup things...
 			noerrHandlerCalled = false // see first deferred function
 
@@ -237,6 +250,7 @@ func TestHandle_noerrHandler(t *testing.T) {
 			test.Require(t, handlerCalled)
 		}()
 
+		defer err2.Handle(&err)
 		defer err2.Handle(&err)
 
 		defer err2.Handle(&err, func(err error) error {

From 9924243dc38fda0fb60cc3ae8c8804f59762e02c Mon Sep 17 00:00:00 2001
From: lainio <harri.lainio@iki.fi>
Date: Sun, 20 Aug 2023 17:56:32 +0300
Subject: [PATCH 13/14] keep werr up-to-date in Info

---
 internal/handler/handler.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/internal/handler/handler.go b/internal/handler/handler.go
index e6d29e4..a97df33 100644
--- a/internal/handler/handler.go
+++ b/internal/handler/handler.go
@@ -79,6 +79,7 @@ func (i *Info) callNilHandler() {
 	}
 	if i.NilHandler != nil {
 		*i.Err = i.NilHandler(i.werr)
+		i.werr = *i.Err // remember change both our errors!
 	} else {
 		i.defaultNilHandler()
 	}
@@ -101,6 +102,7 @@ func (i *Info) callErrorHandler() {
 	i.checkErrorTracer()
 	if i.ErrorHandler != nil {
 		*i.Err = i.ErrorHandler(i.Any.(error))
+		i.werr = *i.Err // remember change both our errors!
 	} else {
 		i.defaultErrorHandler()
 	}
@@ -254,6 +256,7 @@ func PreProcess(errPtr *error, info *Info, a ...any) error {
 	// named return val. Reason is unknown.
 	err := x.Whom(errPtr != nil, *errPtr, nil)
 	info.Err = &err
+	info.werr = *info.Err // remember change both our errors!
 
 	// We want the function who sets the handler, i.e. calls the
 	// err2.Handle function via defer. Because call stack is in reverse

From 7b5af1d01f025812a72a247c55dd9548807bafb3 Mon Sep 17 00:00:00 2001
From: Harri Lainio <harri.lainio@iki.fi>
Date: Sun, 20 Aug 2023 21:28:32 +0300
Subject: [PATCH 14/14] new migration helpers for marginal cases

---
 scripts/README.md    |  8 ++++++--
 scripts/functions.sh | 27 +++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/scripts/README.md b/scripts/README.md
index d8780b0..642e98d 100644
--- a/scripts/README.md
+++ b/scripts/README.md
@@ -9,7 +9,7 @@ successfully from type variables (see below) to Go generics API.
 This readme will guide you to use auto-migration scripts when ever we deprecate
 functions or make something obsolete.
 
-### Auto-Migration of v0.9.40
+### Auto-Migration of v0.9.40 & v0.9.41
 
 The version 0.9.40 is a major update because of the performance and API change.
 We have managed to eliminate `defer` slowdown. Our benchmarks are 3x faster than
@@ -52,7 +52,11 @@ Follow these steps:
 1. Use `git diff` or similar to skimming that all changes seem to be OK. Here
    you have an opportunity to start use new features of `err2` like logging.
 1. You are ready to commit changes.
-
+1. *Problem solving tip.* Use following command to search helper functions:
+   ```shell
+   migr-name.sh -h todo_catch
+   migr-name.sh -h repl_catch
+   ```
 #### Manual Migration With a Location List
 
 Follow these steps check do you have migration needs for v0.9.40:
diff --git a/scripts/functions.sh b/scripts/functions.sh
index 88bf7c0..29266f8 100644
--- a/scripts/functions.sh
+++ b/scripts/functions.sh
@@ -475,6 +475,33 @@ repl_handle_func() {
 }
 
 search_catch_multi='(^\s*)(defer err2\.Catch\(func\(err error\) \{)([\s\S]*?)(^\s*\}\)$)'
+search_catch_multi_with_panic_handler='(^\s*)(defer err2\.Catch\(func\(err error\) \{)([\s\S]*?)(^\s*\}, func\()(\w* any\) \{)'
+# '^\s*\}, func\(\w* any\) \{'         1      2                                       3         4               5
+
+# --- make Catch panic easier
+# '^\s*\}, func\(\w* interface\{\}\) \{'
+search_catch_old_signature='(^\s*\}, func\(\w* )(interface\{\})(\) \{)'
+#                           1                   2              3
+
+todo_catchold_sig() {
+	vlog "searching old Catch panic handler signatures"
+	ag "$search_catch_old_signature"
+}
+
+repl_catchold_sig() {
+	vlog "replacing old Catch panic handler signatures"
+	check_commit "$search_catch_old_signature" '\1any\3'
+}
+
+todo_catchp_func() {
+	vlog "searching old error Catchers"
+	ag "$search_catch_multi_with_panic_handler"
+}
+
+repl_catchp_func() {
+	vlog "replacing old error Catchers with panic"
+	check_commit "$search_catch_multi_with_panic_handler" '\1defer err2.Catch(err2.Err(func(err error) {\3\1}), func(\5'
+}
 
 todo_catch_func() {
 	vlog "searching old error Catchers"