fix(typescript-axios): add useErasableSyntax support for erasableSyntaxOnly compatibility

Add useErasableSyntax option to the typescript-axios generator so that
generated base.ts avoids TypeScript parameter properties (protected/public
in constructor params), which are incompatible with TypeScript 5.8's
erasableSyntaxOnly flag.

Closes #22540

Author: darrell-thobe-sp

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

@@ -53,10 +53,13 @@ public class TypeScriptAxiosClientCodegen extends AbstractTypeScriptClientCodege
     public static final String AXIOS_VERSION = "axiosVersion";
     public static final String DEFAULT_AXIOS_VERSION = "^1.13.5";
     public static final String WITH_AWSV4_SIGNATURE = "withAWSV4Signature";
+    public static final String USE_ERASABLE_SYNTAX = "useErasableSyntax";
+    public static final String USE_ERASABLE_SYNTAX_DESC = "Use erasable syntax for the generated code, compatible with TypeScript's erasableSyntaxOnly option.";
 
     @Getter @Setter
     protected String npmRepository = null;
     protected Boolean stringEnums = false;
+    protected Boolean useErasableSyntax = false;
     protected String importFileExtension = "";
 
     @Getter @Setter
@@ -97,6 +100,7 @@ public TypeScriptAxiosClientCodegen() {
         this.cliOptions.add(new CliOption(USE_SQUARE_BRACKETS_IN_ARRAY_NAMES, "Setting this property to true will add brackets to array attribute names, e.g. my_values[].", SchemaTypeUtil.BOOLEAN_TYPE).defaultValue(Boolean.FALSE.toString()));
         this.cliOptions.add(new CliOption(AXIOS_VERSION, "Use this property to override the axios version in package.json").defaultValue(DEFAULT_AXIOS_VERSION));
         this.cliOptions.add(new CliOption(WITH_AWSV4_SIGNATURE, "whether to include AWS v4 signature support", SchemaTypeUtil.BOOLEAN_TYPE).defaultValue(Boolean.FALSE.toString()));
+        this.cliOptions.add(new CliOption(USE_ERASABLE_SYNTAX, USE_ERASABLE_SYNTAX_DESC, SchemaTypeUtil.BOOLEAN_TYPE).defaultValue(Boolean.FALSE.toString()));
         // Templates have no mapping between formatted property names and original base names so use only "original" and remove this option
         removeOption(CodegenConstants.MODEL_PROPERTY_NAMING);
     }
@@ -177,6 +181,11 @@ public void processOpts() {
             additionalProperties.put("importFileExtension", this.importFileExtension);
         }
 
+        if (additionalProperties.containsKey(USE_ERASABLE_SYNTAX)) {
+            this.useErasableSyntax = Boolean.parseBoolean(additionalProperties.get(USE_ERASABLE_SYNTAX).toString());
+            additionalProperties.put(USE_ERASABLE_SYNTAX, this.useErasableSyntax);
+        }
+
         if (additionalProperties.containsKey(NPM_NAME)) {
             addNpmPackageGeneration();
         }

modules/openapi-generator/src/main/resources/typescript-axios/baseApi.mustache

@@ -25,20 +25,45 @@ export interface RequestArgs {
 
 export class BaseAPI {
     protected configuration: Configuration | undefined;
+{{^useErasableSyntax}}
 
     constructor(configuration?: Configuration, protected basePath: string = BASE_PATH, protected axios: AxiosInstance = globalAxios) {
         if (configuration) {
             this.configuration = configuration;
             this.basePath = configuration.basePath ?? basePath;
         }
     }
+{{/useErasableSyntax}}
+{{#useErasableSyntax}}
+    protected basePath: string;
+    protected axios: AxiosInstance;
+
+    constructor(configuration?: Configuration, basePath: string = BASE_PATH, axios: AxiosInstance = globalAxios) {
+        this.basePath = basePath;
+        this.axios = axios;
+        if (configuration) {
+            this.configuration = configuration;
+            this.basePath = configuration.basePath ?? basePath;
+        }
+    }
+{{/useErasableSyntax}}
 };
 
 export class RequiredError extends Error {
+{{^useErasableSyntax}}
     constructor(public field: string, msg?: string) {
         super(msg);
         this.name = "RequiredError"
     }
+{{/useErasableSyntax}}
+{{#useErasableSyntax}}
+    public field: string;
+    constructor(field: string, msg?: string) {
+        super(msg);
+        this.name = "RequiredError"
+        this.field = field;
+    }
+{{/useErasableSyntax}}
 }
 
 interface ServerMap {

modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/axios/TypeScriptAxiosClientCodegenTest.java

@@ -11,6 +11,7 @@
 import org.testng.annotations.Test;
 
 import java.io.File;
+import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -178,4 +179,44 @@ public void testDeprecatedArrayAttribute() throws Exception {
         // Verify the non-deprecated array property 'nicknames' is also present
         TestUtils.assertFileContains(file, "'nicknames'?: Array<string>");
     }
+
+    @Test(description = "Verify useErasableSyntax generates erasable code in base.ts")
+    public void testUseErasableSyntaxConfig() throws IOException {
+        boolean[] options = {true, false};
+        for (boolean useErasableSyntax : options) {
+            final File output = Files.createTempDirectory("typescript_axios_erasable_").toFile();
+            output.deleteOnExit();
+
+            final CodegenConfigurator configurator = new CodegenConfigurator()
+                    .setGeneratorName("typescript-axios")
+                    .setInputSpec("src/test/resources/3_0/petstore.yaml")
+                    .addAdditionalProperty("useErasableSyntax", useErasableSyntax)
+                    .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+            final ClientOptInput clientOptInput = configurator.toClientOptInput();
+            final DefaultGenerator generator = new DefaultGenerator();
+            final List<File> files = generator.opts(clientOptInput).generate();
+            files.forEach(File::deleteOnExit);
+
+            Path baseTsPath = Paths.get(output + "/base.ts");
+            TestUtils.assertFileExists(baseTsPath);
+            if (useErasableSyntax) {
+                // Erasable syntax: no parameter properties, explicit field declarations and assignments
+                TestUtils.assertFileContains(baseTsPath, "protected basePath: string;");
+                TestUtils.assertFileContains(baseTsPath, "protected axios: AxiosInstance;");
+                TestUtils.assertFileContains(baseTsPath, "this.basePath = basePath;");
+                TestUtils.assertFileContains(baseTsPath, "this.axios = axios;");
+                TestUtils.assertFileContains(baseTsPath, "public field: string;");
+                TestUtils.assertFileContains(baseTsPath, "this.field = field;");
+                // Should NOT contain parameter properties
+                TestUtils.assertFileNotContains(baseTsPath, "protected basePath: string = BASE_PATH,");
+                TestUtils.assertFileNotContains(baseTsPath, "public field: string,");
+            } else {
+                // Non-erasable syntax: uses parameter properties
+                TestUtils.assertFileContains(baseTsPath, "protected basePath: string = BASE_PATH,");
+                TestUtils.assertFileContains(baseTsPath, "protected axios: AxiosInstance = globalAxios");
+                TestUtils.assertFileContains(baseTsPath, "constructor(public field: string,");
+            }
+        }
+    }
 }