Support multilicense LICENSE files generically. (#5310)

Also, add a "flutter build flx --report-licensed-packages" option for
when you need to get the list of the packages affected by licenses.

packages/flutter/lib/src/foundation/licenses.dart

@@ -243,8 +243,14 @@ class LicenseEntryWithLineBreaks extends LicenseEntry {
 /// The flutter tool will automatically collect the contents of all the LICENSE
 /// files found at the root of each package into a single LICENSE file in the
 /// default asset bundle. Each license in that file is separated from the next
-/// by a line of eighty hyphens (`-`). The `services` package registers a
-/// license collector that splits that file and adds each entry to the registry.
+/// by a line of eighty hyphens (`-`), and begins with a list of package names
+/// that the license applies to, one to a line, separated from the next by a
+/// blank line. The `services` package registers a license collector that splits
+/// that file and adds each entry to the registry.
+///
+/// The LICENSE files in each package can either consist of a single license, or
+/// can be in the format described above. In the latter case, each component
+/// license and list of package names is merged independently.
 class LicenseRegistry {
   LicenseRegistry._();
 

packages/flutter_tools/lib/src/asset.dart

@@ -65,9 +65,12 @@ class AssetBundle {
     return stat.modified.isAfter(_lastBuildTimestamp);
   }
 
-  Future<int> build({String manifestPath: defaultManifestPath,
-                     String workingDirPath: defaultWorkingDirPath,
-                     bool includeRobotoFonts: true}) async {
+  Future<int> build({
+    String manifestPath: defaultManifestPath,
+    String workingDirPath: defaultWorkingDirPath,
+    bool includeRobotoFonts: true,
+    bool reportLicensedPackages: false
+  }) async {
     Object manifest = _loadFlutterYamlManifest(manifestPath);
     if (manifest == null) {
       // No manifest file found for this application.
@@ -134,16 +137,16 @@ class AssetBundle {
     if (fontManifest != null)
       entries.add(fontManifest);
 
-    // TODO(ianh): Only do the following line if we've changed packages
-    entries.add(await _obtainLicenses(packageMap, assetBasePath));
+    // TODO(ianh): Only do the following line if we've changed packages or if our LICENSE file changed
+    entries.add(await _obtainLicenses(packageMap, assetBasePath, reportPackages: reportLicensedPackages));
 
     return 0;
   }
 
   void dump() {
-    print('Dumping AssetBundle:');
+    printTrace('Dumping AssetBundle:');
     for (AssetBundleEntry entry in entries) {
-      print(entry.archivePath);
+      printTrace(entry.archivePath);
     }
   }
 }
@@ -219,15 +222,24 @@ final String _licenseSeparator = '\n' + ('-' * 80) + '\n';
 /// Returns a AssetBundleEntry representing the license file.
 Future<AssetBundleEntry> _obtainLicenses(
   PackageMap packageMap,
-  String assetBase
+  String assetBase,
+  { bool reportPackages }
 ) async {
-  // Read the LICENSE file from each package in the .packages file,
-  // splitting each one into each component license (so that we can
-  // de-dupe if possible).
-  // For the sky_engine package we assume each license starts with
-  // package names. For the other packages we assume that each
-  // license is raw.
+  // Read the LICENSE file from each package in the .packages file, splitting
+  // each one into each component license (so that we can de-dupe if possible).
+  //
+  // Individual licenses inside each LICENSE file should be separated by 80
+  // hyphens on their own on a line.
+  //
+  // If a LICENSE file contains more than one component license, then each
+  // component license must start with the names of the packages to which the
+  // component license applies, with each package name on its own line, and the
+  // list of package names separated from the actual license text by a blank
+  // line. (The packages need not match the names of the pub package. For
+  // example, a package might itself contain code from multiple third-party
+  // sources, and might need to include a license for each one.)
   final Map<String, Set<String>> packageLicenses = <String, Set<String>>{};
+  final Set<String> allPackages = new Set<String>();
   for (String packageName in packageMap.map.keys) {
     final Uri package = packageMap.map[packageName];
     if (package != null && package.scheme == 'file') {
@@ -238,7 +250,7 @@ Future<AssetBundleEntry> _obtainLicenses(
         for (String rawLicense in rawLicenses) {
           List<String> packageNames;
           String licenseText;
-          if (packageName == 'sky_engine') {
+          if (rawLicenses.length > 1) {
             final int split = rawLicense.indexOf('\n\n');
             if (split >= 0) {
               packageNames = rawLicense.substring(0, split).split('\n');
@@ -251,11 +263,18 @@ Future<AssetBundleEntry> _obtainLicenses(
           }
           packageLicenses.putIfAbsent(licenseText, () => new Set<String>())
             ..addAll(packageNames);
+          allPackages.addAll(packageNames);
         }
       }
     }
   }
 
+  if (reportPackages) {
+    final List<String> allPackagesList = allPackages.toList()..sort();
+    printStatus('Licenses were found for the following packages:');
+    printStatus(allPackagesList.join(', '));
+  }
+
   final List<String> combinedLicensesList = packageLicenses.keys.map(
     (String license) {
       List<String> packageNames = packageLicenses[license].toList()

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

@@ -22,6 +22,7 @@ class BuildFlxCommand extends BuildSubCommand {
     argParser.addOption('depfile', defaultsTo: defaultDepfilePath);
     argParser.addOption('working-dir', defaultsTo: defaultWorkingDirPath);
     argParser.addFlag('include-roboto-fonts', defaultsTo: true);
+    argParser.addFlag('report-licensed-packages', help: 'Whether to report the names of all the packages that are included in the application\'s LICENSE file.', defaultsTo: false);
     usesPubOption();
   }
 
@@ -49,7 +50,8 @@ class BuildFlxCommand extends BuildSubCommand {
       privateKeyPath: argResults['private-key'],
       workingDirPath: argResults['working-dir'],
       precompiledSnapshot: argResults['precompiled'],
-      includeRobotoFonts: argResults['include-roboto-fonts']
+      includeRobotoFonts: argResults['include-roboto-fonts'],
+      reportLicensedPackages: argResults['report-licensed-packages']
     ).then((int result) {
       if (result == 0)
         printStatus('Built $outputPath.');

packages/flutter_tools/lib/src/flx.dart

@@ -77,7 +77,8 @@ Future<int> build({
   String privateKeyPath: defaultPrivateKeyPath,
   String workingDirPath: defaultWorkingDirPath,
   bool precompiledSnapshot: false,
-  bool includeRobotoFonts: true
+  bool includeRobotoFonts: true,
+  bool reportLicensedPackages: false
 }) async {
   File snapshotFile;
 
@@ -105,7 +106,8 @@ Future<int> build({
     outputPath: outputPath,
     privateKeyPath: privateKeyPath,
     workingDirPath: workingDirPath,
-    includeRobotoFonts: includeRobotoFonts
+    includeRobotoFonts: includeRobotoFonts,
+    reportLicensedPackages: reportLicensedPackages
   );
 }
 
@@ -115,15 +117,19 @@ Future<int> assemble({
   String outputPath: defaultFlxOutputPath,
   String privateKeyPath: defaultPrivateKeyPath,
   String workingDirPath: defaultWorkingDirPath,
-  bool includeRobotoFonts: true
+  bool includeRobotoFonts: true,
+  bool reportLicensedPackages: false
 }) async {
   printTrace('Building $outputPath');
 
   // Build the asset bundle.
   AssetBundle assetBundle = new AssetBundle();
-  int result = await assetBundle.build(manifestPath: manifestPath,
-                                       workingDirPath: workingDirPath,
-                                       includeRobotoFonts: includeRobotoFonts);
+  int result = await assetBundle.build(
+    manifestPath: manifestPath,
+    workingDirPath: workingDirPath,
+    includeRobotoFonts: includeRobotoFonts,
+    reportLicensedPackages: reportLicensedPackages
+  );
   if (result != 0) {
     return result;
   }