Guard localeCompare function

Author: Kanchalai Tanglertsampan

src/compiler/core.ts

@@ -20,6 +20,24 @@ namespace ts {
 
     const createObject = Object.create;
 
+    // More efficient to create a collator once and use its `compare` than to call `a.localeCompare(b)` many times.
+    export const collator: { compare(a: string, b: string): number } = typeof Intl === "object" && typeof Intl.Collator === "function" ? new Intl.Collator() : undefined;
+
+    /**
+     * Use this function instead of calling "String.prototype.localeCompre". This function will preform appropriate check to make sure that
+     *  "typeof Intl" is correct as there are reported issues #11110  nad #11339.
+     * @param a reference string to compare
+     * @param b string to compare against
+     * @param locales string of BCP 47 language tag or an array of string of BCP 47 language tag
+     * @param options an object of Intl.CollatorOptions to specify localeCompare properties
+     */
+    export function localeCompare(a: string, b: string, locales?: string | string[], options?: Intl.CollatorOptions): number | undefined {
+        if (collator && String.prototype.localeCompare) {
+            return a.localeCompare(b, locales, options);
+        }
+        return undefined;
+    }
+
     export function createMap<T>(template?: MapLike<T>): Map<T> {
         const map: Map<T> = createObject(null); // tslint:disable-line:no-null-keyword
 
@@ -1016,8 +1034,8 @@ namespace ts {
         if (a === undefined) return Comparison.LessThan;
         if (b === undefined) return Comparison.GreaterThan;
         if (ignoreCase) {
-            if (String.prototype.localeCompare) {
-                const result = a.localeCompare(b, /*locales*/ undefined, { usage: "sort", sensitivity: "accent" });
+            const result = localeCompare(a, b, /*locales*/ undefined, /*options*/  { usage: "sort", sensitivity: "accent" });
+            if (result) {
                 return result < 0 ? Comparison.LessThan : result > 0 ? Comparison.GreaterThan : Comparison.EqualTo;
             }
 

src/harness/harness.ts

@@ -1634,7 +1634,7 @@ namespace Harness {
 
         export function collateOutputs(outputFiles: Harness.Compiler.GeneratedFile[]): string {
             // Collect, test, and sort the fileNames
-            outputFiles.sort((a, b) => cleanName(a.fileName).localeCompare(cleanName(b.fileName)));
+            outputFiles.sort((a, b) => ts.localeCompare(cleanName(a.fileName), cleanName(b.fileName)));
 
             // Emit them
             let result = "";

src/server/session.ts

@@ -959,7 +959,7 @@ namespace ts.server {
                         result.push({ name, kind, kindModifiers, sortText, replacementSpan: convertedSpan });
                     }
                     return result;
-                }, []).sort((a, b) => a.name.localeCompare(b.name));
+                }, []).sort((a, b) => localeCompare(a.name, b.name));
             }
             else {
                 return completions;

src/services/navigateTo.ts

@@ -188,8 +188,8 @@ namespace ts.NavigateTo {
             // We first sort case insensitively.  So "Aaa" will come before "bar".
             // Then we sort case sensitively, so "aaa" will come before "Aaa".
             return i1.matchKind - i2.matchKind ||
-                i1.name.localeCompare(i2.name, undefined, baseSensitivity) ||
-                i1.name.localeCompare(i2.name);
+                ts.localeCompare(i1.name, i2.name, /*locales*/ undefined, /*options*/ baseSensitivity) ||
+                ts.localeCompare(i1.name, i2.name);
         }
 
         function createNavigateToItem(rawItem: RawNavigateToItem): NavigateToItem {

src/services/navigationBar.ts

@@ -323,10 +323,8 @@ namespace ts.NavigationBar {
         }
     }
 
-    // More efficient to create a collator once and use its `compare` than to call `a.localeCompare(b)` many times.
-    const collator: { compare(a: string, b: string): number } = typeof Intl === "object" && typeof Intl.Collator === "function" ? new Intl.Collator() : undefined;
     // Intl is missing in Safari, and node 0.10 treats "a" as greater than "B".
-    const localeCompareIsCorrect = collator && collator.compare("a", "B") < 0;
+    const localeCompareIsCorrect = ts.collator && ts.collator.compare("a", "B") < 0;
     const localeCompareFix: (a: string, b: string) => number = localeCompareIsCorrect ? collator.compare : function(a, b) {
         // This isn't perfect, but it passes all of our tests.
         for (let i = 0; i < Math.min(a.length, b.length); i++) {
@@ -337,7 +335,7 @@ namespace ts.NavigationBar {
             if (chA === "'" && chB === "\"") {
                 return -1;
             }
-            const cmp = chA.toLocaleLowerCase().localeCompare(chB.toLocaleLowerCase());
+            const cmp = ts.localeCompare(chA.toLocaleLowerCase(), chB.toLocaleLowerCase());
             if (cmp !== 0) {
                 return cmp;
             }