feat: add file.isPublic() function

package.json

@@ -59,6 +59,7 @@
     "date-and-time": "^0.6.3",
     "duplexify": "^3.5.0",
     "extend": "^3.0.0",
+    "gaxios": "^2.0.1",
     "gcs-resumable-upload": "^2.0.0",
     "hash-stream-validation": "^0.2.1",
     "mime": "^2.2.0",

src/file.ts

@@ -57,7 +57,7 @@ import {
 } from '@google-cloud/common/build/src/util';
 const duplexify: DuplexifyConstructor = require('duplexify');
 import {normalize, objectEntries} from './util';
-import {Headers} from 'gaxios';
+import {GaxiosError, Headers, request as gaxiosRequest} from 'gaxios';
 
 export type GetExpirationDateResponse = [Date];
 export interface GetExpirationDateCallback {
@@ -211,6 +211,12 @@ export type MakeFilePrivateResponse = [Metadata];
 
 export interface MakeFilePrivateCallback extends SetFileMetadataCallback {}
 
+export interface IsPublicCallback {
+  (err: Error | null, resp?: boolean): void;
+}
+
+export type IsPublicResponse = [boolean];
+
 export type MakeFilePublicResponse = [Metadata];
 
 export interface MakeFilePublicCallback {
@@ -2595,6 +2601,65 @@ class File extends ServiceObject<File> {
     });
   }
 
+  isPublic(): Promise<IsPublicResponse>;
+  isPublic(callback: IsPublicCallback): void;
+  /**
+   * @callback IsPublicCallback
+   * @param {?Error} err Request error, if any.
+   * @param {boolean} resp Whether file is public or not.
+   */
+  /**
+   * @typedef {array} IsPublicResponse
+   * @property {boolean} 0 Whether file is public or not.
+   */
+  /**
+   * Check whether this file is public or not.
+   * @param {IsPublicCallback} [callback] Callback function.
+   * @returns {Promise<IsPublicResponse>}
+   *
+   * @example
+   * const {Storage} = require('@google-cloud/storage');
+   * const storage = new Storage();
+   * const myBucket = storage.bucket('my-bucket');
+   *
+   * const file = myBucket.file('my-file');
+   *
+   * //-
+   * // Check whether the file is publicly accessible.
+   * //-
+   * file.isPublic(function(err, resp) {
+   *   if (err) {
+   *     console.error(err);
+   *     return;
+   *   }
+   *   console.log(`the file ${file.id} is public: ${resp}`) ;
+   * })
+   * //-
+   * // If the callback is omitted, we'll return a Promise.
+   * //-
+   * file.isPublic().then(function(data) {
+   *   const resp = data[0];
+   * });
+   */
+
+  isPublic(callback?: IsPublicCallback): Promise<IsPublicResponse> | void {
+    gaxiosRequest({
+      method: 'HEAD',
+      url: `http://${
+        this.bucket.name
+      }.storage.googleapis.com/${encodeURIComponent(this.name)}`,
+    }).then(
+      () => callback!(null, true),
+      (err: GaxiosError) => {
+        if (err.code === '403') {
+          callback!(null, false);
+        } else {
+          callback!(err);
+        }
+      }
+    );
+  }
+
   makePrivate(
     options?: MakeFilePrivateOptions
   ): Promise<MakeFilePrivateResponse>;

system-test/storage.ts

@@ -209,17 +209,12 @@ describe('storage', () => {
         bucket = storageWithoutAuth.bucket('gcp-public-data-landsat');
       });
 
-      it('should list and download a file', done => {
-        bucket.getFiles(
-          {
-            autoPaginate: false,
-          },
-          (err, files) => {
-            assert.ifError(err);
-            const file = files![0];
-            file.download(done);
-          }
-        );
+      it('should list and download a file', async () => {
+        const [files] = await bucket.getFiles({autoPaginate: false});
+        const file = files[0];
+        const [isPublic] = await file.isPublic();
+        assert.strictEqual(isPublic, true);
+        assert.doesNotReject(file.download());
       });
     });
 
@@ -232,13 +227,14 @@ describe('storage', () => {
         file = bucket.file(privateFile.id!);
       });
 
-      it('should not download a file', done => {
-        file.download(err => {
-          assert(
-            err!.message.indexOf('does not have storage.objects.get') > -1
-          );
-          done();
-        });
+      it('should not download a file', async () => {
+        const [isPublic] = await file.isPublic();
+        assert.strictEqual(isPublic, false);
+        assert.rejects(
+          file.download(),
+          (err: Error) =>
+            err.message.indexOf('does not have storage.objects.get') > -1
+        );
       });
 
       it('should not upload a file', done => {
@@ -390,7 +386,7 @@ describe('storage', () => {
         const resps = await Promise.all(
           files.map(file => isFilePublicAsync(file))
         );
-        resps.forEach(resp => assert.ok(resp));
+        resps.forEach(resp => assert.strictEqual(resp, true));
         await Promise.all([
           bucket.acl.default.delete({entity: 'allUsers'}),
           bucket.deleteFiles(),
@@ -422,7 +418,9 @@ describe('storage', () => {
         const resps = await Promise.all(
           files.map(file => isFilePublicAsync(file))
         );
-        resps.forEach(resp => assert.ok(!resp));
+        resps.forEach(resp => {
+          assert.strictEqual(resp, false);
+        });
         await bucket.deleteFiles();
       });
     });

test/file.ts

@@ -36,6 +36,7 @@ import * as through from 'through2';
 import * as tmp from 'tmp';
 import * as url from 'url';
 import * as zlib from 'zlib';
+import * as gaxios from 'gaxios';
 
 import {
   Bucket,
@@ -3205,6 +3206,60 @@ describe('File', () => {
     });
   });
 
+  describe('isPublic', () => {
+    const sandbox = sinon.createSandbox();
+
+    afterEach(() => sandbox.restore());
+
+    it('should execute callback with `true` in response', done => {
+      sandbox.stub(gaxios, 'request').resolves();
+      file.isPublic((err: gaxios.GaxiosError, resp: boolean) => {
+        assert.ifError(err);
+        assert.strictEqual(resp, true);
+        done();
+      });
+    });
+
+    it('should execute callback with `false` in response', done => {
+      sandbox.stub(gaxios, 'request').rejects({code: '403'});
+      file.isPublic((err: gaxios.GaxiosError, resp: boolean) => {
+        assert.ifError(err);
+        assert.strictEqual(resp, false);
+        done();
+      });
+    });
+
+    it('should propagate non-403 errors to user', done => {
+      const error = {code: '400'};
+      sandbox.stub(gaxios, 'request').rejects(error as gaxios.GaxiosError);
+      file.isPublic((err: gaxios.GaxiosError) => {
+        assert.strictEqual(err, error);
+        done();
+      });
+    });
+
+    it('should correctly send a HEAD request', done => {
+      const spy = sandbox.spy(gaxios, 'request');
+      file.isPublic((err: gaxios.GaxiosError) => {
+        assert.ifError(err);
+        assert.strictEqual(spy.calledWithMatch({method: 'HEAD'}), true);
+        done();
+      });
+    });
+
+    it('should correctly format URL in the request', done => {
+      const expecterURL = `http://${
+        BUCKET.name
+      }.storage.googleapis.com/${encodeURIComponent(file.name)}`;
+      const spy = sandbox.spy(gaxios, 'request');
+      file.isPublic((err: gaxios.GaxiosError) => {
+        assert.ifError(err);
+        assert.strictEqual(spy.calledWithMatch({url: expecterURL}), true);
+        done();
+      });
+    });
+  });
+
   describe('move', () => {
     describe('copy to destination', () => {
       function assertCopyFile(