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

[thobed]

Summary

Fixes #22540 — [BUG] Typescript-axios code generated is not compatible with erasableSyntaxOnly

TypeScript 5.8 introduced the erasableSyntaxOnly compiler option, which disallows parameter properties (protected/public in constructor parameters). The typescript-axios generator produces code in base.ts that uses parameter properties in both BaseAPI and RequiredError constructors, making the generated code incompatible with this flag.

This PR adds a new useErasableSyntax generator option that, when enabled, replaces parameter properties with explicit field declarations and constructor assignments.

Problem

The generated base.ts contains parameter properties like:

// BaseAPI
constructor(configuration?: Configuration, protected basePath: string = BASE_PATH, protected axios: AxiosInstance = globalAxios) { ... }

// RequiredError
constructor(public field: string, msg?: string) { ... }

These fail compilation when erasableSyntaxOnly: true is set in tsconfig.json (TypeScript 5.8+).

Changes

1. Java Generator (TypeScriptAxiosClientCodegen.java)

• Added useErasableSyntax CLI option (boolean, defaults to false)
• Parses and passes the option through to Mustache templates via additionalProperties

2. Mustache Template (baseApi.mustache)

• Added conditional blocks using {{#useErasableSyntax}} / {{^useErasableSyntax}}
• When enabled: BaseAPI declares basePath and axios as explicit protected fields, assigns them in the constructor body. RequiredError declares field as a public field, assigns it in the constructor body.
• When disabled: behavior is unchanged (existing parameter property syntax)

3. Tests (TypeScriptAxiosClientCodegenTest.java)

• Added testUseErasableSyntaxConfig() test that generates code with both useErasableSyntax: true and useErasableSyntax: false
• Verifies erasable mode produces explicit field declarations and assignments
• Verifies non-erasable mode retains parameter property syntax
• Verifies erasable mode does NOT contain parameter properties

Files Changed

 .../languages/TypeScriptAxiosClientCodegen.java    |  9 +++++
 .../resources/typescript-axios/baseApi.mustache    | 25 +++++++++++++
 .../axios/TypeScriptAxiosClientCodegenTest.java    | 41 ++++++++++++++++++++++
 3 files changed, 75 insertions(+)

Usage

# In your OpenAPI Generator config
generatorName: typescript-axios
additionalProperties:
  useErasableSyntax: "true"

Or via CLI:

openapi-generator-cli generate -g typescript-axios --additional-properties=useErasableSyntax=true -i spec.yaml -o output/

Test Plan

• Build passes: ./mvnw clean install -DskipTests
• TypeScriptAxiosClientCodegenTest.testUseErasableSyntaxConfig passes
• Generated code with useErasableSyntax=true compiles with erasableSyntaxOnly: true
• Generated code without the flag remains unchanged (backward compatible)
• Affected samples regenerated (if applicable)

---

Summary by cubic

Adds a useErasableSyntax option to the typescript-axios generator so base.ts compiles with TypeScript 5.8 erasableSyntaxOnly. Warns when used with stringEnums; tests verify parameter properties (including axios) are removed. Fixes #22540.

• New Features

  • Adds useErasableSyntax (default false).
  • When enabled, BaseAPI and RequiredError use explicit fields and constructor assignments; disabled keeps existing output.
  • Logs a warning if combined with stringEnums.
  • Enable via --additional-properties=useErasableSyntax=true or config additionalProperties.

• Refactors

  • Make the generator logger non-static to align with project ArchUnit rules.

^{Written for commit 30f7c22. Summary will update on new commits.}

[cubic-dev-ai]

2 issues found across 3 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/axios/TypeScriptAxiosClientCodegenTest.java">

<violation number="1" location="modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/axios/TypeScriptAxiosClientCodegenTest.java:213">
P2: The new erasable-syntax test does not assert that the `axios` parameter property is absent, leaving a regression gap for the feature it intends to protect.</violation>
</file>

<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAxiosClientCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAxiosClientCodegen.java:186">
P2: `useErasableSyntax` is not reconciled with `stringEnums`, allowing generation of `export enum` despite claiming erasable-syntax compatibility.</violation>
</file>

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[cubic-dev-ai]

P2: useErasableSyntax is not reconciled with stringEnums, allowing generation of export enum despite claiming erasable-syntax compatibility.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/TypeScriptAxiosClientCodegen.java, line 186:

<comment>`useErasableSyntax` is not reconciled with `stringEnums`, allowing generation of `export enum` despite claiming erasable-syntax compatibility.</comment>

<file context>
@@ -177,6 +181,11 @@ public void processOpts() {
 
+        if (additionalProperties.containsKey(USE_ERASABLE_SYNTAX)) {
+            this.useErasableSyntax = Boolean.parseBoolean(additionalProperties.get(USE_ERASABLE_SYNTAX).toString());
+            additionalProperties.put(USE_ERASABLE_SYNTAX, this.useErasableSyntax);
+        }
+
</file context>

Suggested change

	additionalProperties.put(USE_ERASABLE_SYNTAX, this.useErasableSyntax);
	additionalProperties.put(USE_ERASABLE_SYNTAX, this.useErasableSyntax);
	if (Boolean.TRUE.equals(this.useErasableSyntax) && Boolean.TRUE.equals(this.stringEnums)) {
	this.stringEnums = false;
	additionalProperties.put("stringEnums", false);
	}

[thobed]

Addressed in 0acb15c — added a runtime warning when both useErasableSyntax and stringEnums are enabled. The warning explains that enum declarations are not erasable syntax and recommends disabling stringEnums (the default generates erasable-compatible as const objects).

chose a warning over a hard error to avoid breaking existing configs — users may have valid reasons to enable both (e.g. migrating incrementally).

[thobed]

Thanks for the review!

Finding #1 (missing axios assertion): Fixed in 740a777 — added assertFileNotContains(baseTsPath, "protected axios: AxiosInstance = globalAxios") to the erasable syntax test.

Finding #2 (stringEnums + useErasableSyntax): Looking into this now. When stringEnums=true, the generator produces export enum declarations which are also non-erasable syntax under TypeScript 5.8's erasableSyntaxOnly. Will evaluate whether to add a warning/validation or handle it in this PR.