[typescript-angular] Allow generating discriminator based type visitor

docs/generators/typescript-angular.md

@@ -34,6 +34,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |sortModelPropertiesByRequiredFlag|Sort model properties to place required parameters before optional parameters.| |true|
 |sortParamsByRequiredFlag|Sort method arguments to place required parameters before optional parameters.| |true|
 |stringEnums|Generate string enums instead of objects for enum values.| |false|
+|subtypeVisitor|Use discriminators to create a subtype visitor.| |false|
 |supportsES6|Generate code that conforms to ES6.| |false|
 |taggedUnions|Use discriminators to create tagged unions instead of extending interfaces.| |false|
 |useSingleRequestParameter|Setting this property to true will generate functions with a single argument containing all API endpoint parameters instead of one argument per parameter.| |false|

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAngularClientCodegen.java

@@ -49,6 +49,7 @@ public static enum PROVIDED_IN_LEVEL {none, root, any, platform}
     public static final String WITH_INTERFACES = "withInterfaces";
     public static final String USE_SINGLE_REQUEST_PARAMETER = "useSingleRequestParameter";
     public static final String TAGGED_UNIONS = "taggedUnions";
+    public static final String SUBTYPE_VISITOR = "subtypeVisitor";
     public static final String NG_VERSION = "ngVersion";
     public static final String PROVIDED_IN_ROOT = "providedInRoot";
     public static final String PROVIDED_IN = "providedIn";
@@ -77,6 +78,7 @@ public static enum PROVIDED_IN_LEVEL {none, root, any, platform}
     protected PROVIDED_IN_LEVEL providedIn = PROVIDED_IN_LEVEL.root;
 
     private boolean taggedUnions = false;
+    private boolean subtypeVisitor = false;
 
     public TypeScriptAngularClientCodegen() {
         super();
@@ -106,6 +108,9 @@ public TypeScriptAngularClientCodegen() {
         this.cliOptions.add(CliOption.newBoolean(TAGGED_UNIONS,
                 "Use discriminators to create tagged unions instead of extending interfaces.",
                 this.taggedUnions));
+        this.cliOptions.add(CliOption.newBoolean(SUBTYPE_VISITOR,
+                "Use discriminators to create a subtype visitor.",
+                this.subtypeVisitor));
         this.cliOptions.add(CliOption.newBoolean(PROVIDED_IN_ROOT,
                 "Use this property to provide Injectables in root (it is only valid in angular version greater or equal to 6.0.0). IMPORTANT: Deprecated for angular version greater or equal to 9.0.0, use **providedIn** instead.",
                 false));
@@ -200,6 +205,10 @@ public void processOpts() {
             taggedUnions = Boolean.parseBoolean(additionalProperties.get(TAGGED_UNIONS).toString());
         }
 
+        if (additionalProperties.containsKey(SUBTYPE_VISITOR)) {
+            subtypeVisitor = Boolean.parseBoolean(additionalProperties.get(SUBTYPE_VISITOR).toString());
+        }
+
         if (ngVersion.atLeast("9.0.0") && additionalProperties.containsKey(PROVIDED_IN)) {
             setProvidedIn(additionalProperties.get(PROVIDED_IN).toString());
         } else {
@@ -514,11 +523,18 @@ public Map<String, Object> postProcessAllModels(Map<String, Object> objs) {
                 CodegenModel cm = (CodegenModel) mo.get("model");
                 if (taggedUnions) {
                     mo.put(TAGGED_UNIONS, true);
+                }
+                if (subtypeVisitor) {
+                    mo.put(SUBTYPE_VISITOR, true);
+                }
+                if (taggedUnions || subtypeVisitor) {
                     if (cm.discriminator != null && cm.children != null) {
                         for (CodegenModel child : cm.children) {
                             cm.imports.add(child.classname);
                         }
                     }
+                }
+                if (taggedUnions) {
                     if (cm.parent != null) {
                         cm.imports.remove(cm.parent);
                     }

modules/openapi-generator/src/main/resources/typescript-angular/modelGeneric.mustache

@@ -7,4 +7,4 @@ export interface {{classname}}{{#allParents}}{{#-first}} extends {{/-first}}{{{.
     {{/description}}
     {{#isReadOnly}}readonly {{/isReadOnly}}{{{name}}}{{^required}}?{{/required}}: {{#isEnum}}{{{datatypeWithEnum}}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}}{{#isNullable}} | null{{/isNullable}};
 {{/vars}}
-}{{>modelGenericEnums}}
+}{{>modelGenericEnums}}{{>modelGenericVisitor}}

modules/openapi-generator/src/main/resources/typescript-angular/modelGenericVisitor.mustache

@@ -0,0 +1,29 @@
+{{#subtypeVisitor}}
+    {{#discriminator}}
+
+
+export interface {{classname}}Visitor<R> {
+        {{#discriminator.mappedModels}}
+    visit{{modelName}}(value: {{modelName}}): R;
+        {{/discriminator.mappedModels}}
+}
+
+export function visit{{classname}}<R>(value: {{classname}}, visitor: {{classname}}Visitor<R>): R {
+    switch (value.{{discriminator.propertyName}}) {
+        {{#discriminator.mappedModels}}
+        case '{{mappingName}}':
+            return visitor.visit{{modelName}}(<{{modelName}}>value);
+        {{/discriminator.mappedModels}}
+        default:
+        {{#taggedUnions}}
+            // Make the compiler fail if there is an unmapped member
+            const _exhaustiveCheck: never = value;
+            throw new Error("Unknown model discriminator for '" + value + "'" + _exhaustiveCheck);
+        {{/taggedUnions}}
+        {{^taggedUnions}}
+            throw new Error("Unknown model discriminator '" + value.{{discriminator.propertyName}} + "'");
+        {{/taggedUnions}}
+    }
+}
+    {{/discriminator}}
+{{/subtypeVisitor}}

modules/openapi-generator/src/main/resources/typescript-angular/modelTaggedUnion.mustache

@@ -1,5 +1,6 @@
 {{#discriminator}}
 export type {{classname}} = {{#children}}{{^-first}} | {{/-first}}{{classname}}{{/children}};
+{{>modelGenericVisitor}}
 {{/discriminator}}
 {{^discriminator}}
 {{#parent}}

modules/openapi-generator/src/test/java/org/openapitools/codegen/options/TypeScriptAngularClientOptionsProvider.java

@@ -75,6 +75,7 @@ public Map<String, String> createOptions() {
                 .put(TypeScriptAngularClientCodegen.PROVIDED_IN_ROOT, Boolean.FALSE.toString())
                 .put(TypeScriptAngularClientCodegen.PROVIDED_IN, PROVIDED_IN_LEVEL)
                 .put(TypeScriptAngularClientCodegen.TAGGED_UNIONS, Boolean.FALSE.toString())
+                .put(TypeScriptAngularClientCodegen.SUBTYPE_VISITOR, Boolean.FALSE.toString())
                 .put(TypeScriptAngularClientCodegen.NPM_REPOSITORY, NPM_REPOSITORY)
                 .put(TypeScriptAngularClientCodegen.NG_VERSION, NG_VERSION)
                 .put(TypeScriptAngularClientCodegen.API_MODULE_PREFIX, API_MODULE_PREFIX)