Normalize path slashes for Windows (#285)

src/index.ts

@@ -123,7 +123,7 @@ export function parse (value: string | undefined) {
 /**
  * Replace backslashes with forward slashes.
  */
-export function slash (value: string): string {
+export function normalizeSlashes (value: string): string {
   return value.replace(/\\/g, '/')
 }
 
@@ -386,7 +386,7 @@ export function register (options: Options = {}): () => Register {
  * Check if the filename should be ignored.
  */
 function shouldIgnore (filename: string, ignore: RegExp[], service: () => Register) {
-  const relname = slash(filename)
+  const relname = normalizeSlashes(filename)
 
   return ignore.some(x => x.test(relname))
 }
@@ -445,14 +445,15 @@ function readConfig (compilerOptions: any, project: string | boolean | undefined
   delete result.config.compilerOptions.outFile
   delete result.config.compilerOptions.declarationDir
 
-  const basePath = result.path ? dirname(result.path) : cwd
+  const configPath = result.path && normalizeSlashes(result.path)
+  const basePath = configPath ? dirname(configPath) : normalizeSlashes(cwd)
 
   if (typeof ts.parseConfigFile === 'function') {
     return ts.parseConfigFile(result.config, ts.sys, basePath)
   }
 
   if (typeof ts.parseJsonConfigFileContent === 'function') {
-    return ts.parseJsonConfigFileContent(result.config, ts.sys, basePath, null, result.path as string)
+    return ts.parseJsonConfigFileContent(result.config, ts.sys, basePath, null, configPath as string)
   }
 
   throw new TypeError('Could not find a compatible `parseConfigFile` function')