feature detection in the test environment

Previously it was easy to miss testing generators, because of omitting the `--harmony` flag; even `make full` skipped testing generators.
This commit introduces detecting support for certain syntax oriented language features, before running tests.
We can also assume using Node.js v4 or higher, so generator support is implied.

Makefile

@@ -28,7 +28,7 @@ browser/livescript-min.js:  browser/livescript.js
 package.json: package.json.ls
 	$(LSC) --compile package.json.ls
 
-.PHONY: build build-browser force full install dev-install test test-harmony coverage loc clean
+.PHONY: build build-browser force full install dev-install test coverage loc clean
 
 all: build
 
@@ -51,9 +51,6 @@ dev-install: package.json
 test: build
 	./scripts/test
 
-test-harmony: build
-	node --harmony ./scripts/test
-
 coverage: build
 	$(ISTANBUL) cover ./scripts/test
 

package.json

@@ -35,7 +35,6 @@
   "scripts": {
     "pretest": "make force && make force",
     "test": "make test",
-    "test-harmony": "make test-harmony",
     "posttest": "git checkout -- lib"
   },
   "preferGlobal": true,

package.json.ls

@@ -35,7 +35,6 @@ bin:
 scripts:
   pretest: 'make force && make force'
   test: 'make test'
-  'test-harmony': 'make test-harmony'
   posttest: 'git checkout -- lib'
 
 prefer-global: true

scripts/test

@@ -21,6 +21,15 @@
     return color + text + reset;
   }
 
+  function testSyntax(code) {
+    try {
+      eval(code);
+    } catch (e) {
+      return false;
+    }
+    return true;
+  }
+
   var startTime = Date.now();
   var passedTests = 0;
   var failedTests = 0;
@@ -156,13 +165,7 @@
 
   var files = fs.readdirSync("test");
 
-  if (process.execArgv.indexOf("--harmony") < 0 && process.execArgv.indexOf("--harmony-generators") < 0) {
-    files.splice(files.indexOf("generators.ls"), 1);
-  } else {
-    console.log("Testing with harmony.");
-  }
-  var supportsAsync = parseInt(process.versions.node.split('.')[0]) >= 7;
-  if (supportsAsync) {
+  if (testSyntax("(async function () {})")) {
     console.log("Testing with async.");
   } else {
     files.splice(files.indexOf("async.ls"), 1);