[dartdevc] Fix violations of library_prefix lint

Rename the library prefix used in imports from `JS` to `js_ast`. Create more of
a distinction between:
* `JS` the library.  Now named `js_ast`.
* `js` the const instance of a JSBuilder.
* `JS` the helper to inline javascript in the SDK patches
  and runtime libraries.

Ignore the lint in the js_ast directory to avoid additional diffs for the
eventual un-forking of the package.

Cleanup a few unused imports.

Issue #37218

Change-Id: I039c1048876d9d9ad424fbec3ad555d300845a3d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/106160
Reviewed-by: Nate Bosch <nbosch@google.com>
Reviewed-by: Mark Zhou <markzipan@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>

Author: nshahan

pkg/dev_compiler/analysis_options.yaml

@@ -24,6 +24,7 @@ linter:
     - empty_catches
     - empty_constructor_bodies
     - library_names
+    - library_prefixes
     - no_duplicate_case_values
     - null_closures
     - prefer_contains

pkg/dev_compiler/lib/src/analyzer/code_generator.dart

@@ -15,12 +15,12 @@ import 'package:args/args.dart' show ArgParser, ArgResults;
 import 'package:path/path.dart' as path;
 import 'package:source_maps/source_maps.dart';
 
-import '../compiler/js_names.dart' as JS;
+import '../compiler/js_names.dart' as js_ast;
 import '../compiler/module_builder.dart'
     show transformModuleFormat, ModuleFormat;
 import '../compiler/shared_command.dart';
 import '../compiler/shared_compiler.dart';
-import '../js_ast/js_ast.dart' as JS;
+import '../js_ast/js_ast.dart' as js_ast;
 import '../js_ast/js_ast.dart' show js;
 import '../js_ast/source_map_printer.dart' show SourceMapPrintingContext;
 import 'code_generator.dart' show CodeGenerator;
@@ -95,7 +95,7 @@ JSModuleFile compileWithAnalyzer(
     }
   }
 
-  JS.Program jsProgram;
+  js_ast.Program jsProgram;
   if (options.unsafeForceCompile || !errors.hasFatalErrors) {
     var codeGenerator = CodeGenerator(
         driver,
@@ -227,7 +227,7 @@ class JSModuleFile {
 
   /// The AST that will be used to generate the [code] and [sourceMap] for this
   /// module.
-  final JS.Program moduleTree;
+  final js_ast.Program moduleTree;
 
   /// The compiler options used to generate this module.
   final CompilerOptions options;
@@ -256,20 +256,21 @@ class JSModuleFile {
   // TODO(jmesserly): this should match our old logic, but I'm not sure we are
   // correctly handling the pointer from the .js file to the .map file.
   JSModuleCode getCode(ModuleFormat format, String jsUrl, String mapUrl) {
-    var opts = JS.JavaScriptPrintingOptions(
+    var opts = js_ast.JavaScriptPrintingOptions(
         allowKeywordsInProperties: true, allowSingleLineIfStatements: true);
-    JS.SimpleJavaScriptPrintingContext printer;
+    js_ast.SimpleJavaScriptPrintingContext printer;
     SourceMapBuilder sourceMap;
     if (options.sourceMap) {
       var sourceMapContext = SourceMapPrintingContext();
       sourceMap = sourceMapContext.sourceMap;
       printer = sourceMapContext;
     } else {
-      printer = JS.SimpleJavaScriptPrintingContext();
+      printer = js_ast.SimpleJavaScriptPrintingContext();
     }
 
     var tree = transformModuleFormat(format, moduleTree);
-    tree.accept(JS.Printer(opts, printer, localNamer: JS.TemporaryNamer(tree)));
+    tree.accept(
+        js_ast.Printer(opts, printer, localNamer: js_ast.TemporaryNamer(tree)));
 
     Map builtMap;
     if (options.sourceMap && sourceMap != null) {

pkg/dev_compiler/lib/src/analyzer/module_compiler.dart

@@ -8,8 +8,7 @@ import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart' show InterfaceType;
 import 'package:analyzer/src/dart/element/element.dart' show FieldElementImpl;
 
-import '../compiler/js_names.dart' as JS;
-import '../js_ast/js_ast.dart' as JS;
+import '../compiler/js_names.dart' as js_ast;
 import 'element_helpers.dart';
 import 'extension_types.dart';
 
@@ -176,7 +175,7 @@ class ClassPropertyModel {
   /// pair in JavaScript.
   ///
   /// The value property stores the symbol used for the field's storage slot.
-  final virtualFields = <FieldElement, JS.TemporaryId>{};
+  final virtualFields = <FieldElement, js_ast.TemporaryId>{};
 
   /// The set of inherited getters, used because JS getters/setters are paired,
   /// so if we're generating a setter we may need to emit a getter that calls
@@ -250,7 +249,7 @@ class ClassPropertyModel {
                 covariantParameters != null &&
                 covariantParameters.contains(setter.parameters[0]) &&
                 covariantPrivateMembers.contains(setter)) {
-          virtualFields[field] = JS.TemporaryId(name);
+          virtualFields[field] = js_ast.TemporaryId(name);
         }
       }
     }

pkg/dev_compiler/lib/src/analyzer/property_model.dart

@@ -3,13 +3,14 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:collection';
+
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/member.dart' show TypeParameterMember;
 import 'package:analyzer/dart/element/type.dart';
 
 import '../analyzer/element_helpers.dart';
-import '../compiler/js_names.dart' as JS;
-import '../js_ast/js_ast.dart' as JS;
+import '../compiler/js_names.dart' as js_ast;
+import '../js_ast/js_ast.dart' as js_ast;
 import '../js_ast/js_ast.dart' show js;
 
 Set<TypeParameterElement> freeTypeParameters(DartType t) {
@@ -54,11 +55,11 @@ class _CacheTable {
   // Use a LinkedHashMap to maintain key insertion order so the generated code
   // is stable under slight perturbation.  (If this is not good enough we could
   // sort by name to canonicalize order.)
-  final _names = LinkedHashMap<DartType, JS.TemporaryId>(
+  final _names = LinkedHashMap<DartType, js_ast.TemporaryId>(
       equals: typesAreEqual, hashCode: typeHashCode);
   Iterable<DartType> get keys => _names.keys.toList();
 
-  JS.Statement _dischargeType(DartType type) {
+  js_ast.Statement _dischargeType(DartType type) {
     var name = _names.remove(type);
     if (name != null) {
       return js.statement('let #;', [name]);
@@ -69,8 +70,8 @@ class _CacheTable {
   /// Emit a list of statements declaring the cache variables for
   /// types tracked by this table.  If [typeFilter] is given,
   /// only emit the types listed in the filter.
-  List<JS.Statement> discharge([Iterable<DartType> typeFilter]) {
-    var decls = <JS.Statement>[];
+  List<js_ast.Statement> discharge([Iterable<DartType> typeFilter]) {
+    var decls = <js_ast.Statement>[];
     var types = typeFilter ?? keys;
     for (var t in types) {
       var stmt = _dischargeType(t);
@@ -119,26 +120,26 @@ class _CacheTable {
 
   /// Heuristically choose a good name for the cache and generator
   /// variables.
-  JS.TemporaryId chooseTypeName(DartType type) {
-    return JS.TemporaryId(_typeString(type));
+  js_ast.TemporaryId chooseTypeName(DartType type) {
+    return js_ast.TemporaryId(_typeString(type));
   }
 }
 
 /// _GeneratorTable tracks types which have been
 /// named and hoisted.
 class _GeneratorTable extends _CacheTable {
-  final _defs = LinkedHashMap<DartType, JS.Expression>(
+  final _defs = LinkedHashMap<DartType, js_ast.Expression>(
       equals: typesAreEqual, hashCode: typeHashCode);
 
-  final JS.Identifier _runtimeModule;
+  final js_ast.Identifier _runtimeModule;
 
   _GeneratorTable(this._runtimeModule);
 
   @override
-  JS.Statement _dischargeType(DartType t) {
+  js_ast.Statement _dischargeType(DartType t) {
     var name = _names.remove(t);
     if (name != null) {
-      JS.Expression init = _defs.remove(t);
+      js_ast.Expression init = _defs.remove(t);
       assert(init != null);
       return js.statement('let # = () => ((# = #.constFn(#))());',
           [name, name, _runtimeModule, init]);
@@ -149,7 +150,7 @@ class _GeneratorTable extends _CacheTable {
   /// If [type] does not already have a generator name chosen for it,
   /// assign it one, using [typeRep] as the initializer for it.
   /// Emit the generator name.
-  JS.TemporaryId _nameType(DartType type, JS.Expression typeRep) {
+  js_ast.TemporaryId _nameType(DartType type, js_ast.Expression typeRep) {
     var temp = _names[type];
     if (temp == null) {
       _names[type] = temp = chooseTypeName(type);
@@ -169,12 +170,12 @@ class TypeTable {
   /// parameter.
   final _scopeDependencies = <TypeParameterElement, List<DartType>>{};
 
-  TypeTable(JS.Identifier runtime) : _generators = _GeneratorTable(runtime);
+  TypeTable(js_ast.Identifier runtime) : _generators = _GeneratorTable(runtime);
 
   /// Emit a list of statements declaring the cache variables and generator
   /// definitions tracked by the table.  If [formals] is present, only
   /// emit the definitions which depend on the formals.
-  List<JS.Statement> discharge([List<TypeParameterElement> formals]) {
+  List<js_ast.Statement> discharge([List<TypeParameterElement> formals]) {
     var filter = formals?.expand((p) => _scopeDependencies[p] ?? <DartType>[]);
     var stmts = [_generators].expand((c) => c.discharge(filter)).toList();
     formals?.forEach(_scopeDependencies.remove);
@@ -205,7 +206,8 @@ class TypeTable {
   /// Given a type [type], and a JS expression [typeRep] which implements it,
   /// add the type and its representation to the table, returning an
   /// expression which implements the type (but which caches the value).
-  JS.Expression nameType(ParameterizedType type, JS.Expression typeRep) {
+  js_ast.Expression nameType(
+      ParameterizedType type, js_ast.Expression typeRep) {
     if (!_generators.isNamed(type) && recordScopeDependencies(type)) {
       return typeRep;
     }
@@ -223,10 +225,11 @@ class TypeTable {
   /// should be a function that is invoked to compute the type, rather than the
   /// type itself. This allows better integration with `lazyFn`, avoiding an
   /// extra level of indirection.
-  JS.Expression nameFunctionType(FunctionType type, JS.Expression typeRep,
+  js_ast.Expression nameFunctionType(
+      FunctionType type, js_ast.Expression typeRep,
       {bool lazy = false}) {
     if (!_generators.isNamed(type) && recordScopeDependencies(type)) {
-      return lazy ? JS.ArrowFun([], typeRep) : typeRep;
+      return lazy ? js_ast.ArrowFun([], typeRep) : typeRep;
     }
 
     var name = _generators._nameType(type, typeRep);