feat: public url of a file

src/file.ts

@@ -3061,6 +3061,25 @@ class File extends ServiceObject<File> {
     );
   }
 
+  /**
+   * The public URL of this File
+   * Use {@link File#makePublic} to enable anonymous access via the returned URL.
+   *
+   * @returns {string}
+   *
+   * @example
+   * const {Storage} = require('@google-cloud/storage');
+   * const storage = new Storage();
+   * const bucket = storage.bucket('albums');
+   * const file = bucket.file('my-file');
+   *
+   * file.publicUrl();
+   *  // Will return "https://storage.googleapis.com/albums/my-file"
+   */
+  publicUrl(): string {
+    return `${STORAGE_POST_POLICY_BASE_URL}/${this.bucket.name}/${this.name}`;
+  }
+
   move(
     destination: string | Bucket | File,
     options?: MoveOptions

test/file.ts

@@ -3455,6 +3455,48 @@ describe('File', () => {
     });
   });
 
+  describe('publicUrl', () => {
+    it('should return the public URL', done => {
+      const NAME = 'file-name';
+      const file = new File(BUCKET, NAME);
+      assert.strictEqual(
+        file.publicUrl(),
+        `https://storage.googleapis.com/bucket-name/${NAME}`
+      );
+      done();
+    });
+
+    it('with slash in the name', done => {
+      const NAME = 'parent/child';
+      const file = new File(BUCKET, NAME);
+      assert.strictEqual(
+        file.publicUrl(),
+        `https://storage.googleapis.com/bucket-name/${NAME}`
+      );
+      done();
+    });
+
+    it('with tilde in the name', done => {
+      const NAME = 'foo~bar';
+      const file = new File(BUCKET, NAME);
+      assert.strictEqual(
+        file.publicUrl(),
+        `https://storage.googleapis.com/bucket-name/${NAME}`
+      );
+      done();
+    });
+
+    it('with non ascii in the name', done => {
+      const NAME = '\u2603';
+      const file = new File(BUCKET, NAME);
+      assert.strictEqual(
+        file.publicUrl(),
+        `https://storage.googleapis.com/bucket-name/${NAME}`
+      );
+      done();
+    });
+  });
+
   describe('isPublic', () => {
     const sandbox = sinon.createSandbox();