GetOptions for controlling offline behaviour

packages/firebase/index.d.ts

@@ -1112,6 +1112,37 @@ declare namespace firebase.firestore {
     readonly merge?: boolean;
   }
 
+  /**
+   * An options object that configures the behavior of `get()` calls on
+   * `DocumentReference` and `Query`. By providing a `GetOptions` object, these
+   * methods can be configured to fetch results only from the server, only from
+   * the local cache or attempt to fetch results from the server and fall back to
+   * the cache (which is the default).
+   */
+  export interface GetOptions {
+    /**
+     * Describes whether we should get from server or cache.
+     *
+     * Setting to 'default' (or not setting at all), causes Firestore to try to
+     * retrieve an up-to-date (server-retrieved) snapshot, but fall back to
+     * returning cached data if the server can't be reached.
+     *
+     * Setting to 'server' causes Firestore to avoid the cache, generating an
+     * error if the server cannot be reached. Note that the cache will still be
+     * updated if the server request succeeds. Also note that latency-compensation
+     * still takes effect, so any pending write operations will be visible in the
+     * returned data (merged into the server-provided data).
+     *
+     * Setting to 'cache' causes Firestore to immediately return a value from the
+     * cache, ignoring the server completely (implying that the returned value
+     * may be stale with respect to the value on the server.) If there is no data
+     * in the cache to satisfy the `get()` call, `DocumentReference.get()` will
+     * return an error and `QuerySnapshot.get()` will return an empty
+     * `QuerySnapshot` with no documents.
+     */
+    readonly source?: 'default' | 'server' | 'cache';
+  }
+
   /**
    * A `DocumentReference` refers to a document location in a Firestore database
    * and can be used to write, read, or listen to the location. The document at
@@ -1213,14 +1244,16 @@ declare namespace firebase.firestore {
     /**
      * Reads the document referred to by this `DocumentReference`.
      *
-     * Note: get() attempts to provide up-to-date data when possible by waiting
-     * for data from the server, but it may return cached data or fail if you
-     * are offline and the server cannot be reached.
+     * Note: By default, get() attempts to provide up-to-date data when possible
+     * by waiting for data from the server, but it may return cached data or fail
+     * if you are offline and the server cannot be reached. This behavior can be
+     * altered via the `GetOptions` parameter.
      *
+     * @param options An object to configure the get behavior.
      * @return A Promise resolved with a DocumentSnapshot containing the
      * current document contents.
      */
-    get(): Promise<DocumentSnapshot>;
+    get(options?: GetOptions): Promise<DocumentSnapshot>;
 
     /**
      * Attaches a listener for DocumentSnapshot events. You may either pass
@@ -1598,9 +1631,15 @@ declare namespace firebase.firestore {
     /**
      * Executes the query and returns the results as a QuerySnapshot.
      *
+     * Note: By default, get() attempts to provide up-to-date data when possible
+     * by waiting for data from the server, but it may return cached data or fail
+     * if you are offline and the server cannot be reached. This behavior can be
+     * altered via the `GetOptions` parameter.
+     *
+     * @param options An object to configure the get behavior.
      * @return A Promise that will be resolved with the results of the Query.
      */
-    get(): Promise<QuerySnapshot>;
+    get(options?: GetOptions): Promise<QuerySnapshot>;
 
     /**
      * Attaches a listener for QuerySnapshot events. You may either pass

packages/firestore-types/index.d.ts

@@ -494,6 +494,37 @@ export interface SetOptions {
   readonly merge?: boolean;
 }
 
+/**
+ * An options object that configures the behavior of `get()` calls on
+ * `DocumentReference` and `Query`. By providing a `GetOptions` object, these
+ * methods can be configured to fetch results only from the server, only from
+ * the local cache or attempt to fetch results from the server and fall back to
+ * the cache (which is the default).
+ */
+export interface GetOptions {
+  /**
+   * Describes whether we should get from server or cache.
+   *
+   * Setting to 'default' (or not setting at all), causes Firestore to try to
+   * retrieve an up-to-date (server-retrieved) snapshot, but fall back to
+   * returning cached data if the server can't be reached.
+   *
+   * Setting to 'server' causes Firestore to avoid the cache, generating an
+   * error if the server cannot be reached. Note that the cache will still be
+   * updated if the server request succeeds. Also note that latency-compensation
+   * still takes effect, so any pending write operations will be visible in the
+   * returned data (merged into the server-provided data).
+   *
+   * Setting to 'cache' causes Firestore to immediately return a value from the
+   * cache, ignoring the server completely (implying that the returned value
+   * may be stale with respect to the value on the server.) If there is no data
+   * in the cache to satisfy the `get()` call, `DocumentReference.get()` will
+   * return an error and `QuerySnapshot.get()` will return an empty
+   * `QuerySnapshot` with no documents.
+   */
+  readonly source?: 'default' | 'server' | 'cache';
+}
+
 /**
  * A `DocumentReference` refers to a document location in a Firestore database
  * and can be used to write, read, or listen to the location. The document at
@@ -595,14 +626,16 @@ export class DocumentReference {
   /**
    * Reads the document referred to by this `DocumentReference`.
    *
-   * Note: get() attempts to provide up-to-date data when possible by waiting
-   * for data from the server, but it may return cached data or fail if you
-   * are offline and the server cannot be reached.
+   * Note: By default, get() attempts to provide up-to-date data when possible
+   * by waiting for data from the server, but it may return cached data or fail
+   * if you are offline and the server cannot be reached. This behavior can be
+   * altered via the `GetOptions` parameter.
    *
+   * @param options An object to configure the get behavior.
    * @return A Promise resolved with a DocumentSnapshot containing the
    * current document contents.
    */
-  get(): Promise<DocumentSnapshot>;
+  get(options?: GetOptions): Promise<DocumentSnapshot>;
 
   /**
    * Attaches a listener for DocumentSnapshot events. You may either pass
@@ -976,9 +1009,15 @@ export class Query {
   /**
    * Executes the query and returns the results as a QuerySnapshot.
    *
+   * Note: By default, get() attempts to provide up-to-date data when possible
+   * by waiting for data from the server, but it may return cached data or fail
+   * if you are offline and the server cannot be reached. This behavior can be
+   * altered via the `GetOptions` parameter.
+   *
+   * @param options An object to configure the get behavior.
    * @return A Promise that will be resolved with the results of the Query.
    */
-  get(): Promise<QuerySnapshot>;
+  get(options?: GetOptions): Promise<QuerySnapshot>;
 
   /**
    * Attaches a listener for QuerySnapshot events. You may either pass

packages/firestore/CHANGELOG.md

@@ -10,6 +10,10 @@
   `FirestoreSettings` to `true`. Note that the current behavior
   (`DocumentSnapshot`s returning JS Date objects) will be removed in a future
   release. `Timestamp` supports higher precision than JS Date.
+- [feature] Added ability to control whether DocumentReference.get() and
+  Query.get() should fetch from server only, (by passing { source: 'server' }),
+  cache only (by passing { source: 'cache' }), or attempt server and fall back
+  to the cache (which was the only option previously, and is now the default).
 
 # 0.3.6
 - [fixed] Fixed a regression in the Firebase JS release 4.11.0 that could

packages/firestore/src/api/database.ts

@@ -1000,43 +1000,91 @@ export class DocumentReference implements firestore.DocumentReference {
     };
   }
 
-  get(): Promise<firestore.DocumentSnapshot> {
-    validateExactNumberOfArgs('DocumentReference.get', arguments, 0);
+  get(options?: firestore.GetOptions): Promise<firestore.DocumentSnapshot> {
+    validateOptionNames('DocumentReference.get', options, ['source']);
+    if (options) {
+      validateNamedOptionalPropertyEquals(
+        'DocumentReference.get',
+        'options',
+        'source',
+        options.source,
+        ['default', 'server', 'cache']
+      );
+    }
     return new Promise(
       (resolve: Resolver<firestore.DocumentSnapshot>, reject: Rejecter) => {
-        const unlisten = this.onSnapshotInternal(
-          {
-            includeQueryMetadataChanges: true,
-            includeDocumentMetadataChanges: true,
-            waitForSyncWhenOnline: true
-          },
-          {
-            next: (snap: firestore.DocumentSnapshot) => {
-              // Remove query first before passing event to user to avoid
-              // user actions affecting the now stale query.
-              unlisten();
-
-              if (!snap.exists && snap.metadata.fromCache) {
-                // TODO(dimond): If we're online and the document doesn't
-                // exist then we resolve with a doc.exists set to false. If
-                // we're offline however, we reject the Promise in this
-                // case. Two options: 1) Cache the negative response from
-                // the server so we can deliver that even when you're
-                // offline 2) Actually reject the Promise in the online case
-                // if the document doesn't exist.
-                reject(
-                  new FirestoreError(
-                    Code.ABORTED,
-                    'Failed to get document because the client is ' + 'offline.'
-                  )
-                );
-              } else {
-                resolve(snap);
-              }
-            },
-            error: reject
+        if (options && options.source === 'cache') {
+          this.firestore
+            .ensureClientConfigured()
+            .getDocumentFromLocalCache(this._key)
+            .then((doc: Document) => {
+              resolve(
+                new DocumentSnapshot(
+                  this.firestore,
+                  this._key,
+                  doc,
+                  /*fromCache=*/ true
+                )
+              );
+            }, reject);
+        } else {
+          this.getViaSnapshotListener(resolve, reject, options);
+        }
+      }
+    );
+  }
+
+  private getViaSnapshotListener(
+    resolve: Resolver<firestore.DocumentSnapshot>,
+    reject: Rejecter,
+    options?: firestore.GetOptions
+  ): void {
+    const unlisten = this.onSnapshotInternal(
+      {
+        includeQueryMetadataChanges: true,
+        includeDocumentMetadataChanges: true,
+        waitForSyncWhenOnline: true
+      },
+      {
+        next: (snap: firestore.DocumentSnapshot) => {
+          // Remove query first before passing event to user to avoid
+          // user actions affecting the now stale query.
+          unlisten();
+
+          if (!snap.exists && snap.metadata.fromCache) {
+            // TODO(dimond): If we're online and the document doesn't
+            // exist then we resolve with a doc.exists set to false. If
+            // we're offline however, we reject the Promise in this
+            // case. Two options: 1) Cache the negative response from
+            // the server so we can deliver that even when you're
+            // offline 2) Actually reject the Promise in the online case
+            // if the document doesn't exist.
+            reject(
+              new FirestoreError(
+                Code.UNAVAILABLE,
+                'Failed to get document because the client is ' + 'offline.'
+              )
+            );
+          } else if (
+            snap.exists &&
+            snap.metadata.fromCache &&
+            options &&
+            options.source === 'server'
+          ) {
+            reject(
+              new FirestoreError(
+                Code.UNAVAILABLE,
+                'Failed to get document from server. (However, this ' +
+                  'document does exist in the local cache. Run again ' +
+                  'without setting source to "server" to ' +
+                  'retrieve the cached document.)'
+              )
+            );
+          } else {
+            resolve(snap);
           }
-        );
+        },
+        error: reject
       }
     );
   }
@@ -1619,27 +1667,60 @@ export class Query implements firestore.Query {
     };
   }
 
-  get(): Promise<firestore.QuerySnapshot> {
-    validateExactNumberOfArgs('Query.get', arguments, 0);
+  get(options?: firestore.GetOptions): Promise<firestore.QuerySnapshot> {
+    validateBetweenNumberOfArgs('Query.get', arguments, 0, 1);
     return new Promise(
       (resolve: Resolver<firestore.QuerySnapshot>, reject: Rejecter) => {
-        const unlisten = this.onSnapshotInternal(
-          {
-            includeDocumentMetadataChanges: false,
-            includeQueryMetadataChanges: true,
-            waitForSyncWhenOnline: true
-          },
-          {
-            next: (result: firestore.QuerySnapshot) => {
-              // Remove query first before passing event to user to avoid
-              // user actions affecting the now stale query.
-              unlisten();
-
-              resolve(result);
-            },
-            error: reject
+        if (options && options.source === 'cache') {
+          this.firestore
+            .ensureClientConfigured()
+            .getDocumentsFromLocalCache(this._query)
+            .then((viewSnap: ViewSnapshot) => {
+              resolve(new QuerySnapshot(this.firestore, this._query, viewSnap));
+            }, reject);
+        } else {
+          this.getViaSnapshotListener(resolve, reject, options);
+        }
+      }
+    );
+  }
+
+  private getViaSnapshotListener(
+    resolve: Resolver<firestore.QuerySnapshot>,
+    reject: Rejecter,
+    options?: firestore.GetOptions
+  ): void {
+    const unlisten = this.onSnapshotInternal(
+      {
+        includeDocumentMetadataChanges: false,
+        includeQueryMetadataChanges: true,
+        waitForSyncWhenOnline: true
+      },
+      {
+        next: (result: firestore.QuerySnapshot) => {
+          // Remove query first before passing event to user to avoid
+          // user actions affecting the now stale query.
+          unlisten();
+
+          if (
+            result.metadata.fromCache &&
+            options &&
+            options.source === 'server'
+          ) {
+            reject(
+              new FirestoreError(
+                Code.UNAVAILABLE,
+                'Failed to get documents from server. (However, these ' +
+                  'documents may exist in the local cache. Run again ' +
+                  'without setting source to "server" to ' +
+                  'retrieve the cached documents.)'
+              )
+            );
+          } else {
+            resolve(result);
           }
-        );
+        },
+        error: reject
       }
     );
   }