Merge pull request #11328 from Microsoft/FixTripleSlashCompletions

Fix triple slash completions

src/compiler/core.ts

@@ -1097,7 +1097,9 @@ namespace ts {
         return path.replace(/\\/g, "/");
     }
 
-    // Returns length of path root (i.e. length of "/", "x:/", "//server/share/, file:///user/files")
+    /**
+     * Returns length of path root (i.e. length of "/", "x:/", "//server/share/, file:///user/files")
+    */
     export function getRootLength(path: string): number {
         if (path.charCodeAt(0) === CharacterCodes.slash) {
             if (path.charCodeAt(1) !== CharacterCodes.slash) return 1;
@@ -1126,9 +1128,14 @@ namespace ts {
         return 0;
     }
 
+    /**
+     * Internally, we represent paths as strings with '/' as the directory separator.
+     * When we make system calls (eg: LanguageServiceHost.getDirectory()),
+     * we expect the host to correctly handle paths in our specified format.
+     */
     export const directorySeparator = "/";
     const directorySeparatorCharCode = CharacterCodes.slash;
-    function getNormalizedParts(normalizedSlashedPath: string, rootLength: number) {
+    function getNormalizedParts(normalizedSlashedPath: string, rootLength: number): string[] {
         const parts = normalizedSlashedPath.substr(rootLength).split(directorySeparator);
         const normalized: string[] = [];
         for (const part of parts) {
@@ -1168,6 +1175,11 @@ namespace ts {
         return path.charCodeAt(path.length - 1) === directorySeparatorCharCode;
     }
 
+    /**
+     * Returns the path except for its basename. Eg:
+     * 
+     * /path/to/file.ext -> /path/to
+     */
     export function getDirectoryPath(path: Path): Path;
     export function getDirectoryPath(path: string): string;
     export function getDirectoryPath(path: string): any {