[BUG][typescript-angular] Compile-error TS7030 in configuration.ts when using Basic-Auth and "noImplicitReturns"

Created by: HexagonSun

Description

When generating a typescript-angular client using security schema "basicAuth", the generated configuration.ts does not compile when using typescript's compiler-flag noImplicitReturns.

Although this flag is not enabled by default, Angular's official examples do use it (see e.g. this stackblitz example linked in the Tour of Heroes example here).

openapi-generator version

v5.1.0

The bug occurs in all versions since at least 5.0.0. I've previously used 4.3.0 where the issue did not occur.

OpenAPI declaration file content or url

openapi: 3.0.0
info:
  version: '1.0'
  title: Test API
paths:
  /test:
    get:
      responses:
        default:
          description: test path
components:
    securitySchemes:
        basicAuth:
            type: http
            scheme: basic
security:
    -   basicAuth: []

Generation Details

Nothing special: a regular generation command for a typescript-angular client, see steps to reproduce below.

Steps to reproduce

1. Generate an angular-typescript client from the OpenAPI declaration above

   java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate \
     -i $TMPDIR/configuration-TS7030/issue.yaml \
     -g typescript-angular \
     -o $TMPDIR/configuration-TS7030/client

2. Compile the file using compiler-flag noImplicitReturns

   npx -p typescript tsc \
     --noEmit \
     --lib es2015,dom \
     --noImplicitReturns \
     $TMPDIR/configuration-TS7030/client/configuration.ts

The output shows a compiler error TS7030:

$ npx -p typescript tsc   --noEmit   --lib es2015,dom   --noImplicitReturns   $TMPDIR/configuration-TS7030/client/configuration.ts
../../../../../var/folders/9n/_t8fsm2d4hv8lyjl_zh5873c0000gn/T/configuration-TS7030/client/configuration.ts:1:36 - error TS2307: Cannot find module '@angular/common/http' or its corresponding type declarations.

1 import { HttpParameterCodec } from '@angular/common/http';
                                     ~~~~~~~~~~~~~~~~~~~~~~

../../../../../var/folders/9n/_t8fsm2d4hv8lyjl_zh5873c0000gn/T/configuration-TS7030/client/configuration.ts:63:45 - error TS7030: Not all code paths return a value.

63             this.credentials['basicAuth'] = () => {
                                               ~~~~~~~


Found 2 errors.

(Note that the first error is caused by the generated OpenAPI client not being part of an Angular project).

Related issues/PRs

The issue seems to be a regression of #6944 (closed) / PR 6953

Suggest a fix

The issue is trivially resolved by changing the mustache template configuration.moustache:

diff --git a/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache b/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache
index e3a5e824385..1566cd4c946 100644
--- a/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache
@@ -73,6 +73,7 @@ export class {{configurationClassName}} {
                 if (this.username || this.password) {
                     return btoa(this.username + ':' + this.password);
                 }
+                return undefined;
             };
     {{/isBasicBasic}}
     {{#isBasicBearer}}

Or, a bit nicer using a ternary operator as other methods nearby do, too:

diff --git a/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache b/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache
index e3a5e824385..6c2082f5175 100644
--- a/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-angular/configuration.mustache
@@ -70,9 +70,9 @@ export class {{configurationClassName}} {
 {{#isBasic}}
     {{#isBasicBasic}}
             this.credentials['{{name}}'] = () => {
-                if (this.username || this.password) {
-                    return btoa(this.username + ':' + this.password);
-                }
+                return this.username || this.password
+                    ? btoa(this.username + ':' + this.password)
+                    : undefined;
             };
     {{/isBasicBasic}}
     {{#isBasicBearer}}

Changing the code to always provide a return value does not affect compilation without noImplicitReturns (equally trivially verified by running the steps to reproduce withouth specifying --noImplicitReturns).