Emmet strict mode move, part 2 (#37840)

Continue moving emmet extension to strict mode. This change does the following:

- Remove jsdoc types. These are unused in ts files and can easily get out of date
- Annotate when something can return undefined
- Add null checks for when something can be undefined
- Add explicit types when something can be any

extensions/emmet/src/locateFile.ts

@@ -15,9 +15,8 @@ const reAbsolute = /^\/+/;
 /**
  * Locates given `filePath` on user’s file system and returns absolute path to it.
  * This method expects either URL, or relative/absolute path to resource
- * @param  {String} basePath Base path to use if filePath is not absoulte
- * @param  {String} filePath File to locate. 
- * @return {Promise}
+ * @param basePath Base path to use if filePath is not absoulte
+ * @param filePath File to locate.
  */
 export function locateFile(base: string, filePath: string): Promise<string> {
 	if (/^\w+:/.test(filePath)) {
@@ -34,26 +33,20 @@ export function locateFile(base: string, filePath: string): Promise<string> {
 
 /**
  * Resolves relative file path
- * @param  {TextEditor|String} base
- * @param  {String}            filePath
- * @return {Promise}
  */
-function resolveRelative(basePath, filePath): Promise<string> {
+function resolveRelative(basePath: string, filePath: string): Promise<string> {
 	return tryFile(path.resolve(basePath, filePath));
 }
 
 /**
  * Resolves absolute file path agaist given editor: tries to find file in every
  * parent of editor’s file
- * @param  {TextEditor|String} base
- * @param  {String}            filePath
- * @return {Promise}
  */
-function resolveAbsolute(basePath, filePath): Promise<string> {
+function resolveAbsolute(basePath: string, filePath: string): Promise<string> {
 	return new Promise((resolve, reject) => {
 		filePath = filePath.replace(reAbsolute, '');
 
-		const next = ctx => {
+		const next = (ctx: string) => {
 			tryFile(path.resolve(ctx, filePath))
 				.then(resolve, err => {
 					const dir = path.dirname(ctx);
@@ -71,10 +64,8 @@ function resolveAbsolute(basePath, filePath): Promise<string> {
 
 /**
  * Check if given file exists and it’s a file, not directory
- * @param  {String} file
- * @return {Promise}
  */
-function tryFile(file): Promise<string> {
+function tryFile(file: string): Promise<string> {
 	return new Promise((resolve, reject) => {
 		fs.stat(file, (err, stat) => {
 			if (err) {