Use default runner tool cache location in favor of custom default

Author: iby

action.yml

@@ -8,7 +8,7 @@ inputs:
     description: An explicit key for storing and restoring the cache.
     required: true
   dir:
-    description: A directory path for storing (to) and restoring (from) the cache. Defaults to $SELF_CACHED_DIR or `~/.self-cached` if not set.
+    description: A directory path for storing (to) and restoring (from) the cache. Defaults to $SELF_CACHED_DIR or $RUNNER_TOOL_CACHE if not set.
     required: false
 outputs:
   cache-hit:

product/dist/Restore.js

@@ -13,17 +13,33 @@ beforeEach(() => {
 });
 
 describe('getDirInput', () => {
-  it('can return input value when $SELF_CACHED_DIR is not set', () => {
+  it('can return input value when only $SELF_CACHED_DIR is set', () => {
+    vi.stubEnv('SELF_CACHED_DIR', 'foo');
+    vi.stubEnv('RUNNER_TOOL_CACHE', undefined);
+    expect(getDirInput('baz')).toBe('baz');
+    expect(getDirInput(undefined)).toBe('foo');
+  });
+
+  it('can return input value when only $RUNNER_TOOL_CACHE is set', () => {
     vi.stubEnv('SELF_CACHED_DIR', undefined);
-    expect(getDirInput('foo')).toBe('foo');
-    expect(getDirInput(undefined)).toBe(path.join(os.homedir(), '.self-cached'));
+    vi.stubEnv('RUNNER_TOOL_CACHE', 'foo');
+    expect(getDirInput('baz')).toBe('baz');
+    expect(getDirInput(undefined)).toBe('foo');
   });
 
-  it('can return input value when $SELF_CACHED_DIR is set', () => {
+  it('can return input value when both $SELF_CACHED_DIR and $RUNNER_TOOL_CACHE are set', () => {
     vi.stubEnv('SELF_CACHED_DIR', 'foo');
-    expect(getDirInput('bar')).toBe('bar');
+    vi.stubEnv('RUNNER_TOOL_CACHE', 'bar');
+    expect(getDirInput('baz')).toBe('baz');
     expect(getDirInput(undefined)).toBe('foo');
   });
+
+  it("can't return input value when neither $SELF_CACHED_DIR or $RUNNER_TOOL_CACHE are not set", () => {
+    vi.stubEnv('SELF_CACHED_DIR', undefined);
+    vi.stubEnv('RUNNER_TOOL_CACHE', undefined);
+    expect(getDirInput('baz')).toBe('baz');
+    expect(getDirInput(undefined)).toBe(undefined);
+  });
 });
 
 describe('getLocalPath', () => {

product/dist/Store.js

@@ -23,7 +23,7 @@ export enum State {
 export function getDirInput(value: string | undefined): string {
   if (value) return value;
   if (process.env.SELF_CACHED_DIR) return process.env.SELF_CACHED_DIR;
-  return path.join(os.homedir(), '.self-cached');
+  return process.env.RUNNER_TOOL_CACHE!;
 }
 
 export async function getLocalPath(inputPath: string): Promise<{ path: string; name: string; exists: boolean }> {