Only process the tsconfig once.

Author: chriskrycho

lib/typescript-preprocessor.js

@@ -24,16 +24,18 @@ class TypeScriptPreprocessor {
     this.name = 'ember-cli-typescript';
     this.ext = 'ts';
     this.options = JSON.parse(JSON.stringify(options));
-  }
 
-  toTree(inputNode, inputPath, outputPath) {
-    const tsconfig = readConfig(path.join('.', 'tsconfig.json'));
+    const tsconfig = readConfig(path.join('.', 'tsconfig.json'))
 
     // tsc needs to emit files on the broccoli pipeline, but not in the default
     // config. Otherwise its compiled `.js` files may be created inadvertently.
     tsconfig.compilerOptions.noEmit = false;
     delete tsconfig.compilerOptions.outDir;
 
+    this.tsconfig = tsconfig;
+  }
+
+  toTree(inputNode, inputPath, outputPath) {
     const js = new Funnel(inputNode, {
       exclude: [/ts$/],
       annotation: 'JS files',
@@ -43,7 +45,7 @@ class TypeScriptPreprocessor {
       annotation: 'TS files',
     });
 
-    const ts = tsc(tsFiles, { tsconfig });
+    const ts = tsc(tsFiles, { tsconfig: this.tsconfig });
 
     // Put everything together.
     return new MergeTrees([js, ts], {