Add github_api_url input defaulting to env.GITHUB_API_URL (#43)

action.yml

@@ -14,6 +14,8 @@ inputs:
     description: The full name of the repository for which the token will be requested (defaults to the current repository).
   permissions:
     description: The JSON-stringified permissions granted to the token (defaults to all the GitHub app permissions, see https://docs.github.com/en/rest/apps/apps#create-an-installation-access-token-for-an-app).
+  github_api_url:
+    description: The API URL of the GitHub server, such as https://api.github.com. Defaults to the environment variable GITHUB_API_URL, see https://docs.github.com/en/actions/reference/environment-variables#default-environment-variables.
 outputs:
   token:
     description: An installation token for the GitHub App on the requested repository.

src/fetch-installation-token.ts

@@ -1,18 +1,19 @@
-import { env } from "node:process";
 import { getOctokit } from "@actions/github";
 import { createAppAuth } from "@octokit/auth-app";
 import { request } from "@octokit/request";
 import ensureError from "ensure-error";
 
 export const fetchInstallationToken = async ({
   appId,
+  baseUrl,
   installationId,
   owner,
   permissions,
   privateKey,
   repo,
 }: Readonly<{
   appId: string;
+  baseUrl: URL;
   installationId?: number;
   owner: string;
   permissions?: Record<string, string>;
@@ -23,9 +24,7 @@ export const fetchInstallationToken = async ({
     appId,
     privateKey,
     request: request.defaults({
-      // GITHUB_API_URL is part of GitHub Actions' built-in environment variables.
-      // See https://docs.github.com/en/actions/reference/environment-variables#default-environment-variables.
-      baseUrl: env.GITHUB_API_URL,
+      baseUrl: baseUrl.toString().replace(/\/+$/, ''),
     }),
   });
 

src/index.ts

@@ -1,4 +1,5 @@
 import { Buffer } from "node:buffer";
+import { env } from "node:process";
 import { getInput, info, setFailed, setOutput, setSecret } from "@actions/core";
 import { context } from "@actions/github";
 import ensureError from "ensure-error";
@@ -29,8 +30,16 @@ const run = async () => {
       ? repositoryInput.split("/")
       : [context.repo.owner, context.repo.repo];
 
+    // GITHUB_API_URL is part of GitHub Actions' built-in environment variables.
+    // See https://docs.github.com/en/actions/reference/environment-variables#default-environment-variables.
+    const githubUrlInput = getInput("github_api_url");
+    const baseUrl = githubUrlInput
+      ? new URL(githubUrlInput)
+      : new URL(env.GITHUB_API_URL!);
+
     const installationToken = await fetchInstallationToken({
       appId,
+      baseUrl,
       installationId,
       owner,
       permissions,