have flutter precache print if there's no work to do (#3213)

* have flutter precache print if there's no work to do

* tweak precache

packages/flutter_tools/lib/src/cache.dart

@@ -38,19 +38,29 @@ class Cache {
     return new Directory(path.join(getCacheArtifacts().path, name));
   }
 
-  String getVersionFor(String kArtifactName) {
-    File versionFile = new File(path.join(getRoot().path, '$kArtifactName.version'));
+  String getVersionFor(String artifactName) {
+    File versionFile = new File(path.join(getRoot().path, '$artifactName.version'));
     return versionFile.existsSync() ? versionFile.readAsStringSync().trim() : null;
   }
 
-  String getStampFor(String kArtifactName) {
-    File stampFile = new File(path.join(getRoot().path, '$kArtifactName.stamp'));
+  String getStampFor(String artifactName) {
+    File stampFile = getStampFileFor(artifactName);
     return stampFile.existsSync() ? stampFile.readAsStringSync().trim() : null;
   }
 
-  void setStampFor(String kArtifactName, String version) {
-    File stampFile = new File(path.join(getRoot().path, '$kArtifactName.stamp'));
-    stampFile.writeAsStringSync(version);
+  void setStampFor(String artifactName, String version) {
+    getStampFileFor(artifactName).writeAsStringSync(version);
+  }
+
+  File getStampFileFor(String artifactName) {
+    return new File(path.join(getRoot().path, '$artifactName.stamp'));
+  }
+
+  bool isUpToDate() {
+    MaterialFonts materialFonts = new MaterialFonts(cache);
+    FlutterEngine engine = new FlutterEngine(cache);
+
+    return materialFonts.isUpToDate() && engine.isUpToDate();
   }
 
   Future<String> getThirdPartyFile(String urlStr, String serviceName, {

packages/flutter_tools/lib/src/commands/precache.dart

@@ -6,7 +6,7 @@ import 'dart:async';
 
 import 'package:args/command_runner.dart';
 
-import '../cache.dart';
+import '../globals.dart';
 
 class PrecacheCommand extends Command {
   @override
@@ -17,7 +17,11 @@ class PrecacheCommand extends Command {
 
   @override
   Future<int> run() async {
-    await Cache.instance.updateAll();
+    if (cache.isUpToDate())
+      printStatus('All up-to-date.');
+    else
+      await cache.updateAll();
+
     return 0;
   }
 }

packages/flutter_tools/lib/src/dart/pub.dart

@@ -18,7 +18,7 @@ bool _shouldRunPubGet({ File pubSpecYaml, File dotPackages }) {
   DateTime dotPackagesLastModified = dotPackages.lastModifiedSync();
   if (pubSpecYaml.lastModifiedSync().isAfter(dotPackagesLastModified))
     return true;
-  File flutterToolsStamp = new File(path.join(Cache.instance.getRoot().path, 'flutter_tools.stamp'));
+  File flutterToolsStamp = Cache.instance.getStampFileFor('flutter_tools');
   if (flutterToolsStamp.lastModifiedSync().isAfter(dotPackagesLastModified))
     return true;
   return false;