From 949c517fdd1526eaadc70f906cd98829db97e4e5 Mon Sep 17 00:00:00 2001
From: Andy Hanson <anhans@microsoft.com>
Date: Mon, 15 Aug 2016 13:45:33 -0700
Subject: [PATCH] Add `multiMapAdd` helper

---
 src/compiler/core.ts                           | 15 +++++++++++++++
 src/compiler/emitter.ts                        |  2 +-
 src/compiler/sys.ts                            |  2 +-
 src/harness/fourslash.ts                       |  3 +--
 src/harness/unittests/tsserverProjectSystem.ts |  6 ++----
 src/services/services.ts                       |  3 +--
 6 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 27b27bc653292..8ac46f9df0df6 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -566,6 +566,21 @@ namespace ts {
         return result;
     }
 
+    /**
+     * Adds the value to an array of values associated with the key, and returns the array.
+     * Creates the array if it does not already exist.
+     */
+    export function multiMapAdd<V>(map: Map<V[]>, key: string, value: V): V[] {
+        const values = map[key];
+        if (values) {
+            values.push(value);
+            return values;
+        }
+        else {
+            return map[key] = [value];
+        }
+    }
+
     /**
      * Tests whether a value is an array.
      */
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 357a15507a457..74553dac20e04 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -6847,7 +6847,7 @@ const _super = (function (geti, seti) {
                                 // export { x, y }
                                 for (const specifier of (<ExportDeclaration>node).exportClause.elements) {
                                     const name = (specifier.propertyName || specifier.name).text;
-                                    (exportSpecifiers[name] || (exportSpecifiers[name] = [])).push(specifier);
+                                    multiMapAdd(exportSpecifiers, name, specifier);
                                 }
                             }
                             break;
diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index 350d75429b754..458cbc99a4758 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -267,7 +267,7 @@ namespace ts {
                 }
 
                 function addFileWatcherCallback(filePath: string, callback: FileWatcherCallback): void {
-                    (fileWatcherCallbacks[filePath] || (fileWatcherCallbacks[filePath] = [])).push(callback);
+                    multiMapAdd(fileWatcherCallbacks, filePath, callback);
                 }
 
                 function addFile(fileName: string, callback: FileWatcherCallback): WatchedFile {
diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index b5fa53763cb9d..aece7b5c3ec7b 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -1635,8 +1635,7 @@ namespace FourSlash {
             const result = ts.createMap<Range[]>();
             for (const range of this.getRanges()) {
                 const text = this.rangeText(range);
-                const ranges = result[text] || (result[text] = []);
-                ranges.push(range);
+                ts.multiMapAdd(result, text, range);
             }
             return result;
         }
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index 49f033b9defcb..89def128f9e16 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -198,8 +198,7 @@ namespace ts {
 
         watchDirectory(directoryName: string, callback: DirectoryWatcherCallback, recursive: boolean): DirectoryWatcher {
             const path = this.toPath(directoryName);
-            const callbacks = this.watchedDirectories[path] || (this.watchedDirectories[path] = []);
-            callbacks.push({ cb: callback, recursive });
+            const callbacks = multiMapAdd(this.watchedDirectories, path, { cb: callback, recursive });
             return {
                 referenceCount: 0,
                 directoryName,
@@ -239,8 +238,7 @@ namespace ts {
 
         watchFile(fileName: string, callback: FileWatcherCallback) {
             const path = this.toPath(fileName);
-            const callbacks = this.watchedFiles[path] || (this.watchedFiles[path] = []);
-            callbacks.push(callback);
+            const callbacks = multiMapAdd(this.watchedFiles, path, callback);
             return {
                 close: () => {
                     const i = callbacks.indexOf(callback);
diff --git a/src/services/services.ts b/src/services/services.ts
index 9ef14315cb6e9..1c28495dcac40 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -984,8 +984,7 @@ namespace ts {
             function addDeclaration(declaration: Declaration) {
                 const name = getDeclarationName(declaration);
                 if (name) {
-                    const declarations = getDeclarations(name);
-                    declarations.push(declaration);
+                    multiMapAdd(result, name, declaration);
                 }
             }