feat(typescript-angular): add withHttpResource option for signal-based GET resources

Opt-in, Angular 20+. Every GET operation without a request body gets a
<operation>Resource method next to its Observable method, returning an
Angular httpResource (httpResource.text or httpResource.blob when the
response is text or binary). Writes keep only their Observable method.

The query, header and credential code moves into a partial shared by
both paths, so the output of every existing configuration is unchanged.
Adds a sample build inside typescript-angular-v22-provided-in-root with
an HttpTestingController spec.

Author: thekhegay

bin/configs/typescript-angular-v22-with-http-resource.yaml

@@ -0,0 +1,8 @@
+generatorName: typescript-angular
+outputDir: samples/client/petstore/typescript-angular-v22-provided-in-root/builds/with-http-resource
+inputSpec: modules/openapi-generator/src/test/resources/3_0/typescript-angular/http-resource.yaml
+templateDir: modules/openapi-generator/src/main/resources/typescript-angular
+additionalProperties:
+  ngVersion: 22.0.0
+  supportsES6: true
+  withHttpResource: true

docs/generators/typescript-angular.md

@@ -55,6 +55,7 @@ These options may be applied as additional-properties (cli) or configOptions (pl
 |tsVersion|The version of typescript compatible with Angular (see ngVersion option).| |null|
 |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|
 |useSquareBracketsInArrayNames|Setting this property to true will add brackets to array attribute names, e.g. my_values[].| |false|
+|withHttpResource|Setting this property to true will generate, next to the Observable method of each GET operation without a request body, a method returning a signal-based Angular httpResource. Requires Angular v20+.| |false|
 |withInterfaces|Setting this property to true will generate interfaces next to the default class implementations.| |false|
 |zonejsVersion|The version of zone.js compatible with Angular (see ngVersion option).| |null|
 

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

@@ -38,6 +38,7 @@
 
 import java.io.File;
 import java.util.*;
+import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
@@ -59,6 +60,9 @@ public static enum QUERY_PARAM_OBJECT_FORMAT_TYPE {dot, json, key}
 
     public static enum PROVIDED_IN_LEVEL {none, root, any, platform}
 
+    // same expression as Configuration.isJsonMime in configuration.mustache
+    private static final Pattern JSON_MIME_PATTERN = Pattern.compile("^(application/json|[^;/ \\t]+/[^;/ \\t]+[+]json)[ \\t]*(;.*)?$", Pattern.CASE_INSENSITIVE);
+
     private static final String DEFAULT_IMPORT_PREFIX = "./";
     private static final String DEFAULT_MODEL_IMPORT_DIRECTORY_PREFIX = "../";
 
@@ -86,6 +90,13 @@ public static enum PROVIDED_IN_LEVEL {none, root, any, platform}
     public static final String RXJS_VERSION = "rxjsVersion";
     public static final String NGPACKAGR_VERSION = "ngPackagrVersion";
     public static final String ZONEJS_VERSION = "zonejsVersion";
+    public static final String WITH_HTTP_RESOURCE = "withHttpResource";
+
+    public static final String X_ANGULAR_HTTP_RESOURCE = "x-angular-http-resource";
+    public static final String X_ANGULAR_HTTP_RESOURCE_FACTORY = "x-angular-http-resource-factory";
+    public static final String X_ANGULAR_HTTP_RESOURCE_TYPE = "x-angular-http-resource-type";
+    public static final String X_ANGULAR_HTTP_RESOURCE_ACCEPT = "x-angular-http-resource-accept";
+    public static final String X_ANGULAR_REQUEST_PARAMS_INTERFACE = "x-angular-request-params-interface";
 
     protected String ngVersion = "22.0.0";
     @Getter @Setter
@@ -101,6 +112,7 @@ 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 withHttpResource = false;
 
     public TypeScriptAngularClientCodegen() {
         super();
@@ -131,6 +143,10 @@ public TypeScriptAngularClientCodegen() {
         this.cliOptions.add(CliOption.newBoolean(USE_SINGLE_REQUEST_PARAMETER,
                 "Setting this property to true will generate functions with a single argument containing all API endpoint parameters instead of one argument per parameter.",
                 false));
+        this.cliOptions.add(CliOption.newBoolean(WITH_HTTP_RESOURCE,
+                "Setting this property to true will generate, next to the Observable method of each GET operation without a request body, "
+                        + "a method returning a signal-based Angular httpResource. Requires Angular v20+.",
+                false));
         this.cliOptions.add(CliOption.newBoolean(TAGGED_UNIONS,
                 "Use discriminators to create tagged unions instead of extending interfaces.",
                 this.taggedUnions));
@@ -221,6 +237,17 @@ public void processOpts() {
             throw new IllegalArgumentException("Invalid ngVersion: " + ngVersion + ". Only Angular v9+ is supported.");
         }
 
+        if (additionalProperties.containsKey(WITH_HTTP_RESOURCE)) {
+            withHttpResource = convertPropertyToBoolean(WITH_HTTP_RESOURCE);
+        }
+        if (withHttpResource && !ngVersion.atLeast("20.0.0")) {
+            throw new IllegalArgumentException("Invalid ngVersion: " + ngVersion + ". " + WITH_HTTP_RESOURCE + " requires Angular v20+.");
+        }
+        writePropertyBack(WITH_HTTP_RESOURCE, withHttpResource);
+        if (withHttpResource) {
+            supportingFiles.add(new SupportingFile("httpResourceOptions.mustache", getIndexDirectory(), "http.resource.options.ts"));
+        }
+
         if (additionalProperties.containsKey(NPM_NAME)) {
             addNpmPackageGeneration(ngVersion);
         }
@@ -423,13 +450,24 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap operations, L
         objs.put("apiFilename", getApiFilenameFromClassname(objs.getClassname()));
 
         List<CodegenOperation> ops = objs.getOperation();
+        Set<String> nicknames = ops.stream().map(op -> op.nickname).collect(Collectors.toSet());
         boolean hasSomeFormParams = false;
         boolean hasSomeEncodableParams = false;
+        boolean hasSomeHttpResource = false;
         for (CodegenOperation op : ops) {
             if (op.getHasFormParams()) {
                 hasSomeFormParams = true;
             }
             op.httpMethod = op.httpMethod.toLowerCase(Locale.ENGLISH);
+            if (markHttpResource(op, nicknames)) {
+                hasSomeHttpResource = true;
+            }
+            // the <Operation>RequestParams interface: for every operation with useSingleRequestParameter, else for the resource methods only
+            if (op.getHasParams() && (getUseSingleRequestParameter() || op.vendorExtensions.containsKey(X_ANGULAR_HTTP_RESOURCE))) {
+                op.vendorExtensions.put(X_ANGULAR_REQUEST_PARAMS_INTERFACE, true);
+            } else {
+                op.vendorExtensions.remove(X_ANGULAR_REQUEST_PARAMS_INTERFACE);
+            }
             // deduplicate auth methods by name (as they will lead to duplicate code):
             op.authMethods =
                     op.authMethods != null ? op.authMethods.stream().collect(Collectors.collectingAndThen(Collectors.toCollection(() -> new TreeSet<>(Comparator.comparing(x -> x.name))), ArrayList::new))
@@ -474,6 +512,7 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap operations, L
 
         operations.put("hasSomeFormParams", hasSomeFormParams);
         operations.put("hasSomeEncodableParams", hasSomeEncodableParams);
+        operations.put("hasSomeHttpResource", hasSomeHttpResource);
 
         // Add additional filename information for model imports in the services
         List<Map<String, String>> imports = operations.getImports();
@@ -486,6 +525,61 @@ public OperationsMap postProcessOperationsWithModels(OperationsMap operations, L
         return operations;
     }
 
+    /**
+     * Marks a GET operation without a request body for an additional httpResource method.
+     * The factory mirrors the responseType the Observable method picks at runtime for the default
+     * Accept header (Configuration.selectHeaderAccept): JSON (or no produces) uses httpResource,
+     * text uses httpResource.text, anything else, and file responses, httpResource.blob.
+     *
+     * @param op        the operation, with its http method already lower-cased
+     * @param nicknames the nicknames of all operations of the same API class
+     * @return true if the operation gets a resource method
+     */
+    private boolean markHttpResource(CodegenOperation op, Set<String> nicknames) {
+        op.vendorExtensions.remove(X_ANGULAR_HTTP_RESOURCE);
+        if (!withHttpResource || !"get".equals(op.httpMethod) || op.getHasBodyOrFormParams()) {
+            return false;
+        }
+        String resourceName = op.nickname + "Resource";
+        if (nicknames.contains(resourceName) || nicknames.contains(resourceName + "Request")) {
+            LOGGER.warn("Not generating {} for operation {}: the name is taken by another operation.", resourceName, op.operationId);
+            return false;
+        }
+
+        List<String> produces = op.produces == null ? Collections.emptyList() : op.produces.stream()
+                .map(mediaType -> mediaType.get("mediaType"))
+                .filter(Objects::nonNull)
+                .collect(Collectors.toList());
+        String accept = produces.stream()
+                .filter(mediaType -> JSON_MIME_PATTERN.matcher(mediaType).matches())
+                .findFirst()
+                .orElse(produces.isEmpty() ? null : produces.get(0));
+
+        String factory;
+        String type;
+        if (op.isResponseFile) {
+            factory = ".blob";
+            type = "Blob";
+        } else if (accept != null && accept.startsWith("text")) {
+            factory = ".text";
+            type = "string";
+        } else if (accept == null || JSON_MIME_PATTERN.matcher(accept).matches()) {
+            factory = "";
+            type = op.returnType != null ? op.returnType : "any";
+        } else {
+            factory = ".blob";
+            type = "Blob";
+        }
+
+        op.vendorExtensions.put(X_ANGULAR_HTTP_RESOURCE, true);
+        op.vendorExtensions.put(X_ANGULAR_HTTP_RESOURCE_FACTORY, factory);
+        op.vendorExtensions.put(X_ANGULAR_HTTP_RESOURCE_TYPE, type);
+        if (accept != null) {
+            op.vendorExtensions.put(X_ANGULAR_HTTP_RESOURCE_ACCEPT, accept);
+        }
+        return true;
+    }
+
     @Override
     public ModelsMap postProcessModels(ModelsMap objs) {
         ModelsMap result = super.postProcessModels(objs);

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

@@ -160,6 +160,49 @@ export const appConfig: ApplicationConfig = {
 };
 ```
 
+{{#withHttpResource}}
+### Signal-based resources
+
+Every `GET` operation without a request body also has a `...Resource` method, next to its Observable method,
+which returns an Angular [`HttpResourceRef`](https://angular.dev/api/common/http/HttpResourceRef)
+(see [`httpResource`](https://angular.dev/guide/http/http-resource)):
+
+```typescript
+import { Component, computed, inject, input } from '@angular/core';
+import { PetService } from '{{npmName}}';
+
+@Component({
+    selector: 'app-pet',
+    templateUrl: './pet.component.html',
+})
+export class PetComponent {
+    readonly petId = input.required<number>();
+
+    // requested again whenever petId changes
+    readonly pet = inject(PetService).getPetByIdResource(() => ({ petId: this.petId() }));
+
+    readonly name = computed(() => this.pet.hasValue() ? this.pet.value().name : '');
+}
+```
+
+- The first argument returns the request parameters and is called in a reactive context: every signal it reads
+  sends a new request when it changes. While it returns `undefined`, or a required parameter is `null` or `undefined`,
+  the resource stays idle. Operations without parameters take no such argument, and it can be left out when all
+  parameters are optional.
+- Call the method in an injection context (a field initializer or a constructor), or pass an `injector` in the options.
+  The resource belongs to that injector: it is destroyed with it, and it sends its request through the `HttpClient`
+  of that injector, so the interceptors of the caller apply.
+- The credentials of the `{{configurationClassName}}` are read each time the request is built, so a credential
+  function that reads a signal sends a new request when the signal changes. Other credential changes need `reload()`.
+- `transferCache` defaults to `true`, as for the Observable methods. Angular's transfer cache skips requests with an
+  `Authorization` header unless `includeRequestsWithAuthHeaders` is set in `withHttpTransferCacheOptions`.
+- Resources are generated for reads only. A resource cancels its pending request when its parameters change, which
+  is not safe for a write, so operations that change data keep only their Observable method.
+
+The `withHttpResource` option requires Angular 20 or later. `httpResource` is stable since Angular 22 and
+experimental in Angular 20 and 21.
+
+{{/withHttpResource}}
 ### Customizing path parameter encoding
 
 Without further customization, only [path-parameters][parameter-locations-url] of [style][style-values-url] 'simple'

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

@@ -5,6 +5,9 @@ import { Inject, Injectable, Optional }                      from '@angular/core
 import { HttpClient, HttpHeaders, HttpParams,
          HttpResponse, HttpEvent{{#httpContextInOptions}}, HttpContext {{/httpContextInOptions}}
         }       from '@angular/common/http';
+{{#hasSomeHttpResource}}
+import { HttpResourceRef, HttpResourceRequest, httpResource } from '@angular/common/http';
+{{/hasSomeHttpResource}}
 import { Observable }                                        from 'rxjs';
 import { OpenApiHttpParams, QueryParamStyle } from '../query.params';
 
@@ -17,29 +20,30 @@ import { {{ classname }} } from '{{ filename }}';
 import { BASE_PATH, COLLECTION_FORMATS }                     from '../variables';
 import { {{configurationClassName}} }                                     from '../configuration';
 import { BaseService } from '../api.base.service';
+{{#hasSomeHttpResource}}
+import { ApiHttpResourceOptions } from '../http.resource.options';
+{{/hasSomeHttpResource}}
 {{#withInterfaces}}
 import {
-    {{classname}}Interface{{#useSingleRequestParameter}}{{#operations}}{{#operation}}{{#allParams.0}},
-    {{#prefixParameterInterfaces}}{{classname}}{{/prefixParameterInterfaces}}{{operationIdCamelCase}}RequestParams{{/allParams.0}}{{/operation}}{{/operations}}{{/useSingleRequestParameter}}
+    {{classname}}Interface{{#operations}}{{#operation}}{{#vendorExtensions.x-angular-request-params-interface}},
+    {{#prefixParameterInterfaces}}{{classname}}{{/prefixParameterInterfaces}}{{operationIdCamelCase}}RequestParams{{/vendorExtensions.x-angular-request-params-interface}}{{/operation}}{{/operations}}
 } from './{{classFilename}}Interface';
 {{/withInterfaces}}
 
 {{#operations}}
 
 {{^withInterfaces}}
-{{#useSingleRequestParameter}}
 {{#operation}}
-{{#allParams.0}}
+{{#vendorExtensions.x-angular-request-params-interface}}
 export interface {{#prefixParameterInterfaces}}{{classname}}{{/prefixParameterInterfaces}}{{operationIdCamelCase}}RequestParams {
 {{#allParams}}
     {{#description}}/** {{.}} */
     {{/description}}{{paramName}}{{^required}}?{{/required}}: {{{dataType}}}{{#isNullable}} | null{{/isNullable}};
 {{/allParams}}
 }
 
-{{/allParams.0}}
+{{/vendorExtensions.x-angular-request-params-interface}}
 {{/operation}}
-{{/useSingleRequestParameter}}
 {{/withInterfaces}}
 
 {{#description}}
@@ -107,90 +111,7 @@ export class {{classname}} extends BaseService {
 {{/required}}
 {{/allParams}}
 
-{{#hasQueryParamsOrAuth}}
-        let localVarQueryParameters = new OpenApiHttpParams(this.encoder);
-{{#queryParams}}
-
-        localVarQueryParameters = this.addToHttpParams(
-            localVarQueryParameters,
-            '{{baseName}}',
-            <any>{{paramName}},
-            {{#isQueryParamObjectFormatJson}}
-            QueryParamStyle.Json,
-            {{/isQueryParamObjectFormatJson}}
-            {{^isQueryParamObjectFormatJson}}
-            {{^style}}
-            {{#queryIsJsonMimeType}}
-            QueryParamStyle.Json,
-            {{/queryIsJsonMimeType}}
-            {{^queryIsJsonMimeType}}
-            QueryParamStyle.Form,
-            {{/queryIsJsonMimeType}}
-            {{/style}}
-            {{#style}}
-            {{#isDeepObject}}
-            QueryParamStyle.DeepObject,
-            {{/isDeepObject}}
-            {{#isFormStyle}}
-            QueryParamStyle.Form,
-            {{/isFormStyle}}
-            {{#isSpaceDelimited}}
-            QueryParamStyle.SpaceDelimited,
-            {{/isSpaceDelimited}}
-            {{#isPipeDelimited}}
-            QueryParamStyle.PipeDelimited,
-            {{/isPipeDelimited}}
-            {{#queryIsJsonMimeType}}
-            QueryParamStyle.Json,
-            {{/queryIsJsonMimeType}}
-            {{/style}}
-            {{/isQueryParamObjectFormatJson}}
-            {{isExplode}},
-        );
-
-{{/queryParams}}
-
-{{/hasQueryParamsOrAuth}}
-        let localVarHeaders = this.defaultHeaders;
-{{#headerParams}}
-        {{#isArray}}
-        if ({{paramName}}) {
-            localVarHeaders = localVarHeaders.set('{{baseName}}', [...{{paramName}}].join(COLLECTION_FORMATS['{{collectionFormat}}']));
-        }
-        {{/isArray}}
-        {{^isArray}}
-        if ({{paramName}} !== undefined && {{paramName}} !== null) {
-            localVarHeaders = localVarHeaders.set('{{baseName}}', String({{paramName}}));
-        }
-        {{/isArray}}
-{{/headerParams}}
-
-{{#authMethods}}
-        // authentication ({{name}}) required
-{{#isApiKey}}
-    {{#isKeyInHeader}}
-        localVarHeaders = this.configuration.addCredentialToHeaders('{{name}}', '{{keyParamName}}', localVarHeaders);
-    {{/isKeyInHeader}}
-    {{#isKeyInQuery}}
-        localVarQueryParameters = this.configuration.addCredentialToQuery('{{name}}', '{{keyParamName}}', localVarQueryParameters);
-    {{/isKeyInQuery}}
-{{/isApiKey}}
-{{#isBasic}}
-    {{#isBasicBasic}}
-        localVarHeaders = this.configuration.addCredentialToHeaders('{{name}}', 'Authorization', localVarHeaders, 'Basic ');
-    {{/isBasicBasic}}
-    {{#isBasicBearer}}
-        localVarHeaders = this.configuration.addCredentialToHeaders('{{name}}', 'Authorization', localVarHeaders, 'Bearer ');
-    {{/isBasicBearer}}
-{{/isBasic}}
-{{#isOAuth}}
-        localVarHeaders = this.configuration.addCredentialToHeaders('{{name}}', 'Authorization', localVarHeaders, 'Bearer ');
-{{/isOAuth}}
-{{#isOpenId}}
-        localVarHeaders = this.configuration.addCredentialToHeaders('{{name}}', 'Authorization', localVarHeaders, 'Bearer ');
-{{/isOpenId}}
-
-{{/authMethods}}
+{{>apiRequestQueryAndHeaders}}
         const localVarHttpHeaderAcceptSelected: string | undefined = options?.httpHeaderAccept ?? this.configuration.selectHeaderAccept([
     {{#produces}}
             '{{{mediaType}}}'{{^-last}},{{/-last}}
@@ -328,5 +249,8 @@ export class {{classname}} extends BaseService {
         );
     }
 
+{{#vendorExtensions.x-angular-http-resource}}
+{{>apiHttpResource}}
+{{/vendorExtensions.x-angular-http-resource}}
 {{/operation}}}
 {{/operations}}