Make some easy optimizations

Author: andrewbranch

src/compiler/core.ts

@@ -1634,6 +1634,26 @@ namespace ts {
         };
     }
 
+    export function memoizeOne<ArgsT extends unknown[], ReturnT>(callback: (...args: ArgsT) => ReturnT) {
+        let value: ReturnT;
+        let cachedArgs: ArgsT;
+        return (...args: ArgsT) => {
+            const length = args.length;
+            if (cachedArgs && cachedArgs.length === length) {
+                for (let i = 0; i < length; i++) {
+                    if (args[i] !== cachedArgs[i]) {
+                        cachedArgs = args;
+                        return value = callback(...args);
+                    }
+                }
+                return value;
+            }
+            cachedArgs = args;
+            return value = callback(...args);
+        };
+    }
+
+
     /**
      * High-order function, composes functions. Note that functions are composed inside-out;
      * for example, `compose(a, b)` is the equivalent of `x => b(a(x))`.

src/compiler/moduleSpecifiers.ts

@@ -173,7 +173,7 @@ namespace ts.moduleSpecifiers {
         return [getPathFromPathComponents(aParts), getPathFromPathComponents(bParts)];
     }
 
-    function discoverProbableSymlinks(files: ReadonlyArray<SourceFile>, getCanonicalFileName: GetCanonicalFileName, cwd: string): ReadonlyMap<string> {
+    const discoverProbableSymlinks = memoizeOne((files: ReadonlyArray<SourceFile>, getCanonicalFileName: GetCanonicalFileName, cwd: string): ReadonlyMap<string> => {
         const result = createMap<string>();
         const symlinks = flatten<readonly [string, string]>(mapDefined(files, sf =>
             sf.resolvedModules && compact(arrayFrom(mapIterator(sf.resolvedModules.values(), res =>
@@ -183,7 +183,7 @@ namespace ts.moduleSpecifiers {
             result.set(commonOriginal, commonResolved);
         }
         return result;
-    }
+    });
 
     /**
      * Looks for existing imports that use symlinks to this module.

src/services/codefixes/importFixes.ts

@@ -593,6 +593,9 @@ namespace ts.codefix {
         });
 
         function getNodeModulesPackageNameFromFileName(importedFileName: string): string | undefined {
+            if (!stringContains(importedFileName, "node_modules")) {
+                return undefined;
+            }
             const specifier = moduleSpecifiers.getModuleSpecifier(
                 compilerOptions,
                 from,