3 files changed, 28 insertions, 4 deletions
diff --git a/js/compiler.ts b/js/compiler.ts
index 624aab201..f0f82ffb1 100644
--- a/js/compiler.ts
+++ b/js/compiler.ts
@@ -169,6 +169,8 @@ export class DenoCompiler
   // A reference to the global scope so it can be monkey patched during
   // testing
   private _window = window;
+  // Flags forcing recompilation of TS code
+  public recompile = false;
 
   /**
    * Drain the run queue, retrieving the arguments for the module
@@ -412,11 +414,15 @@ export class DenoCompiler
 
   /**
    * Retrieve the output of the TypeScript compiler for a given module and
-   * cache the result.
+   * cache the result. Re-compilation can be forced using '--recompile' flag.
    */
   compile(moduleMetaData: ModuleMetaData): OutputCode {
-    this._log("compiler.compile", moduleMetaData.fileName);
-    if (moduleMetaData.outputCode) {
+    const recompile = !!this.recompile;
+    this._log(
+        "compiler.compile",
+        { filename: moduleMetaData.fileName, recompile }
+    );
+    if (!recompile && moduleMetaData.outputCode) {
       return moduleMetaData.outputCode;
     }
     const { fileName, sourceCode } = moduleMetaData;
diff --git a/js/compiler_test.ts b/js/compiler_test.ts
index fdb5fe03b..fef18ec3d 100644
--- a/js/compiler_test.ts
+++ b/js/compiler_test.ts
@@ -458,6 +458,23 @@ test(function compilerGetScriptFileNames() {
   teardown();
 });
 
+test(function compilerRecompileFlag() {
+  setup();
+  compilerInstance.run("foo/bar.ts", "/root/project");
+  assertEqual(getEmitOutputStack.length, 1, "Expected only a single emitted file.");
+  // running compiler against same file should use cached code
+  compilerInstance.run("foo/bar.ts", "/root/project");
+  assertEqual(getEmitOutputStack.length, 1, "Expected only a single emitted file.");
+  compilerInstance.recompile = true;
+  compilerInstance.run("foo/bar.ts", "/root/project");
+  assertEqual(getEmitOutputStack.length, 2, "Expected two emitted file.");
+  assert(
+      getEmitOutputStack[0] === getEmitOutputStack[1],
+      "Expected same file to be emitted twice."
+  );
+  teardown();
+});
+
 test(function compilerGetScriptKind() {
   assertEqual(compilerInstance.getScriptKind("foo.ts"), ts.ScriptKind.TS);
   assertEqual(compilerInstance.getScriptKind("foo.d.ts"), ts.ScriptKind.TS);
diff --git a/js/main.ts b/js/main.ts
index e927710a7..63d72e87f 100644
--- a/js/main.ts
+++ b/js/main.ts
@@ -37,7 +37,7 @@ export default function denoMain() {
   libdeno.setGlobalErrorHandler(onGlobalError);
   const compiler = DenoCompiler.instance();
 
-  // First we send an empty "Start" message to let the privlaged side know we
+  // First we send an empty "Start" message to let the privileged side know we
   // are ready. The response should be a "StartRes" message containing the CLI
   // args and other info.
   const startResMsg = sendStart();
@@ -68,5 +68,6 @@ export default function denoMain() {
     os.exit(0);
   }
 
+  compiler.recompile = startResMsg.recompileFlag();
   compiler.run(inputFn, `${cwd}/`);
 }