Pull allowed extensions from grammar definitions

lib/main/atom/utils/atom.ts

@@ -1,4 +1,5 @@
 import * as Atom from "atom"
+import {memoize, throttle} from "lodash"
 import * as path from "path"
 import {FileLocationQuery, Location, pointToLocation} from "./ts"
 
@@ -17,9 +18,10 @@ export function isTypescriptFile(filePath: string | undefined): boolean {
 }
 
 export function typeScriptScopes(): ReadonlyArray<string> {
-  const tsScopes = atom.config.get("atom-typescript").tsSyntaxScopes
-  if (atom.config.get("atom-typescript").allowJS) {
-    tsScopes.push(...atom.config.get("atom-typescript").jsSyntaxScopes)
+  const config = atom.config.get("atom-typescript")
+  const tsScopes = config.tsSyntaxScopes
+  if (config.allowJS) {
+    tsScopes.push(...config.jsSyntaxScopes)
   }
   return tsScopes
 }
@@ -33,13 +35,36 @@ export function isTypescriptGrammar(editor: Atom.TextEditor): boolean {
   return typeScriptScopes().includes(scopeName)
 }
 
-function isAllowedExtension(ext: string) {
-  const tsExts = atom.config.get("atom-typescript").tsFileExtensions
-  if (atom.config.get("atom-typescript").allowJS) {
-    tsExts.push(...atom.config.get("atom-typescript").jsFileExtensions)
+function notNullary<T>(x: T | undefined | null): x is T {
+  return x != null
+}
+
+function memoizeThrottle<T, U>(func: (arg: T) => U, wait: number): (arg: T) => U {
+  const mem = memoize((_param: T) => throttle(func, wait, {leading: true}))
+  return (param: T) => mem(param)(param)! // NOTE: leading MUST be true for this ! to hold
+}
+
+const isAllowedExtension = memoizeThrottle((ext: string) => {
+  const config = atom.config.get("atom-typescript")
+  const tsExts = config.tsFileExtensions
+  if (config.allowJS) {
+    tsExts.push(...config.jsFileExtensions)
+  }
+  if (config.extensionsFromGrammars) {
+    const custom = atom.config.get("core.customFileTypes") ?? {}
+    const scopes = typeScriptScopes()
+    tsExts.push(
+      ...([] as Array<string | undefined>)
+        .concat(
+          ...scopes.map((scope) => atom.grammars.grammarForScopeName(scope)?.fileTypes),
+          ...scopes.map((scope) => custom[scope]),
+        )
+        .filter(notNullary)
+        .map((s) => `.${s}`),
+    )
   }
   return tsExts.includes(ext)
-}
+}, 5000)
 
 export function getFilePathPosition(
   editor: Atom.TextEditor,

lib/typings/atom-config.d.ts

@@ -37,6 +37,7 @@ declare module "atom" {
     "atom-typescript.suppressAllDiagnostics": boolean
     "atom-typescript.tsFileExtensions": string[]
     "atom-typescript.jsFileExtensions": string[]
+    "atom-typescript.extensionsFromGrammars": boolean
     "atom-typescript.tsSyntaxScopes": string[]
     "atom-typescript.jsSyntaxScopes": string[]
     "atom-typescript.allowJS": boolean
@@ -77,6 +78,7 @@ declare module "atom" {
       suppressAllDiagnostics: boolean
       tsFileExtensions: string[]
       jsFileExtensions: string[]
+      extensionsFromGrammars: boolean
       tsSyntaxScopes: string[]
       jsSyntaxScopes: string[]
       allowJS: boolean

lib/typings/atom.d.ts

@@ -18,4 +18,7 @@ declare module "atom" {
   interface TextEditorElement {
     setUpdatedSynchronously(val: boolean): void
   }
+  interface Grammar {
+    fileTypes: string[]
+  }
 }

package.json

@@ -281,6 +281,13 @@
       ],
       "order": 140
     },
+    "extensionsFromGrammars": {
+      "title": "Determine file extensions from Atom grammar settings",
+      "description": "Pull recognized file extensions from grammar definitions matching the syntax scopes defined below",
+      "type": "boolean",
+      "default": true,
+      "order": 145
+    },
     "tsSyntaxScopes": {
       "title": "TypeScript syntax scopes",
       "description": "Comma-separated list of TypeScript syntax scopes; may require Atom restart to take effect; DO NOT EDIT unless you know what you are doing",