fix: change exists to return false on error code 5 (#353)

src/database.js

@@ -146,39 +146,6 @@ class Database extends ServiceObject {
        *   });
        */
       create: true,
-      /**
-       * @typedef {array} DatabaseExistsResponse
-       * @property {boolean} 0 Whether the {@link Database} exists.
-       */
-      /**
-       * @callback DatabaseExistsCallback
-       * @param {?Error} err Request error, if any.
-       * @param {boolean} exists Whether the {@link Database} exists.
-       */
-      /**
-       * Check if a database exists.
-       *
-       * @method Database#exists
-       * @param {DatabaseExistsCallback} [callback] Callback function.
-       * @returns {Promise<DatabaseExistsResponse>}
-       *
-       * @example
-       * const {Spanner} = require('@google-cloud/spanner');
-       * const spanner = new Spanner();
-       *
-       * const instance = spanner.instance('my-instance');
-       * const database = instance.database('my-database');
-       *
-       * database.exists(function(err, exists) {});
-       *
-       * //-
-       * // If the callback is omitted, we'll return a Promise.
-       * //-
-       * database.exists().then(function(data) {
-       *   const exists = data[0];
-       * });
-       */
-      exists: true,
     };
 
     const formattedName_ = Database.formatName_(instance.formattedName_, name);
@@ -547,6 +514,51 @@ class Database extends ServiceObject {
       );
     });
   }
+  /**
+   * @typedef {array} DatabaseExistsResponse
+   * @property {boolean} 0 Whether the {@link Database} exists.
+   */
+  /**
+   * @callback DatabaseExistsCallback
+   * @param {?Error} err Request error, if any.
+   * @param {boolean} exists Whether the {@link Database} exists.
+   */
+  /**
+   * Check if a database exists.
+   *
+   * @method Database#exists
+   * @param {DatabaseExistsCallback} [callback] Callback function.
+   * @returns {Promise<DatabaseExistsResponse>}
+   *
+   * @example
+   * const {Spanner} = require('@google-cloud/spanner');
+   * const spanner = new Spanner();
+   *
+   * const instance = spanner.instance('my-instance');
+   * const database = instance.database('my-database');
+   *
+   * database.exists(function(err, exists) {});
+   *
+   * //-
+   * // If the callback is omitted, we'll return a Promise.
+   * //-
+   * database.exists().then(function(data) {
+   *   const exists = data[0];
+   * });
+   */
+  exists(callback) {
+    const NOT_FOUND = 5;
+
+    this.getMetadata(function(err) {
+      if (err && err.code !== NOT_FOUND) {
+        callback(err, null);
+        return;
+      }
+
+      const exists = !err || err.code !== NOT_FOUND;
+      callback(null, exists);
+    });
+  }
   /**
    * @typedef {array} GetDatabaseResponse
    * @property {Database} 0 The {@link Database}.

src/instance.js

@@ -91,38 +91,6 @@ class Instance extends common.ServiceObject {
        *   });
        */
       create: true,
-      /**
-       * @typedef {array} InstanceExistsResponse
-       * @property {boolean} 0 Whether the {@link Instance} exists.
-       */
-      /**
-       * @callback InstanceExistsCallback
-       * @param {?Error} err Request error, if any.
-       * @param {boolean} exists Whether the {@link Instance} exists.
-       */
-      /**
-       * Check if an instance exists.
-       *
-       * @method Instance#exists
-       * @param {InstanceExistsCallback} [callback] Callback function.
-       * @returns {Promise<InstanceExistsResponse>}
-       *
-       * @example
-       * const {Spanner} = require('@google-cloud/spanner');
-       * const spanner = new Spanner();
-       *
-       * const instance = spanner.instance('my-instance');
-       *
-       * instance.exists(function(err, exists) {});
-       *
-       * //-
-       * // If the callback is omitted, we'll return a Promise.
-       * //-
-       * instance.exists().then(function(data) {
-       *   const exists = data[0];
-       * });
-       */
-      exists: true,
     };
     super({
       parent: spanner,
@@ -363,6 +331,50 @@ class Instance extends common.ServiceObject {
         );
       });
   }
+  /**
+   * @typedef {array} InstanceExistsResponse
+   * @property {boolean} 0 Whether the {@link Instance} exists.
+   */
+  /**
+   * @callback InstanceExistsCallback
+   * @param {?Error} err Request error, if any.
+   * @param {boolean} exists Whether the {@link Instance} exists.
+   */
+  /**
+   * Check if an instance exists.
+   *
+   * @method Instance#exists
+   * @param {InstanceExistsCallback} [callback] Callback function.
+   * @returns {Promise<InstanceExistsResponse>}
+   *
+   * @example
+   * const {Spanner} = require('@google-cloud/spanner');
+   * const spanner = new Spanner();
+   *
+   * const instance = spanner.instance('my-instance');
+   *
+   * instance.exists(function(err, exists) {});
+   *
+   * //-
+   * // If the callback is omitted, we'll return a Promise.
+   * //-
+   * instance.exists().then(function(data) {
+   *   const exists = data[0];
+   * });
+   */
+  exists(callback) {
+    const NOT_FOUND = 5;
+
+    this.getMetadata(function(err) {
+      if (err && err.code !== NOT_FOUND) {
+        callback(err, null);
+        return;
+      }
+
+      const exists = !err || err.code !== NOT_FOUND;
+      callback(null, exists);
+    });
+  }
   /**
    * @typedef {array} GetInstanceResponse
    * @property {Instance} 0 The {@link Instance}.

system-test/spanner.js

@@ -733,6 +733,22 @@ describe('Spanner', function() {
         })
       );
     });
+
+    it('should return true for instances that exist', function(done) {
+      instance.exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, true);
+        done();
+      });
+    });
+
+    it('should return false for instances that do not exist', function(done) {
+      spanner.instance('bad-instance').exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, false);
+        done();
+      });
+    });
   });
 
   describe('instanceConfigs', function() {
@@ -834,6 +850,22 @@ describe('Spanner', function() {
         );
     });
 
+    it('should return true for databases that exist', function(done) {
+      database.exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, true);
+        done();
+      });
+    });
+
+    it('should return false for databases that do not exist', function(done) {
+      instance.database('bad-database').exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, false);
+        done();
+      });
+    });
+
     it('should create a table', function(done) {
       const createTableStatement = `
         CREATE TABLE Singers (

test/database.js

@@ -209,10 +209,7 @@ describe('Database', function() {
 
       assert.strictEqual(calledWith.parent, instanceInstance);
       assert.strictEqual(calledWith.id, NAME);
-      assert.deepStrictEqual(calledWith.methods, {
-        create: true,
-        exists: true,
-      });
+      assert.deepStrictEqual(calledWith.methods, {create: true});
 
       calledWith.createMethod(null, options, done);
     });
@@ -550,6 +547,48 @@ describe('Database', function() {
     });
   });
 
+  describe('exists', function() {
+    it('should return any non-404 like errors', function(done) {
+      const error = {code: 3};
+
+      database.getMetadata = function(callback) {
+        callback(error);
+      };
+
+      database.exists(function(err, exists) {
+        assert.strictEqual(err, error);
+        assert.strictEqual(exists, null);
+        done();
+      });
+    });
+
+    it('should return true if error is absent', function(done) {
+      database.getMetadata = function(callback) {
+        callback(null);
+      };
+
+      database.exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, true);
+        done();
+      });
+    });
+
+    it('should return false if not found error if present', function(done) {
+      const error = {code: 5};
+
+      database.getMetadata = function(callback) {
+        callback(error);
+      };
+
+      database.exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, false);
+        done();
+      });
+    });
+  });
+
   describe('get', function() {
     it('should call getMetadata', function(done) {
       const options = {};

test/instance.js

@@ -144,10 +144,7 @@ describe('Instance', function() {
 
       assert.strictEqual(calledWith.parent, spannerInstance);
       assert.strictEqual(calledWith.id, NAME);
-      assert.deepStrictEqual(calledWith.methods, {
-        create: true,
-        exists: true,
-      });
+      assert.deepStrictEqual(calledWith.methods, {create: true});
 
       calledWith.createMethod(null, options, done);
     });
@@ -428,6 +425,48 @@ describe('Instance', function() {
     });
   });
 
+  describe('exists', function() {
+    it('should return any non-404 like errors', function(done) {
+      const error = {code: 3};
+
+      instance.getMetadata = function(callback) {
+        callback(error);
+      };
+
+      instance.exists(function(err, exists) {
+        assert.strictEqual(err, error);
+        assert.strictEqual(exists, null);
+        done();
+      });
+    });
+
+    it('should return true if error is absent', function(done) {
+      instance.getMetadata = function(callback) {
+        callback(null);
+      };
+
+      instance.exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, true);
+        done();
+      });
+    });
+
+    it('should return false if not found error if present', function(done) {
+      const error = {code: 5};
+
+      instance.getMetadata = function(callback) {
+        callback(error);
+      };
+
+      instance.exists(function(err, exists) {
+        assert.ifError(err);
+        assert.strictEqual(exists, false);
+        done();
+      });
+    });
+  });
+
   describe('get', function() {
     it('should call getMetadata', function(done) {
       const options = {};