Allow --dry-run

Author: sigurdm

lib/src/command/cache_gc.dart

@@ -36,10 +36,16 @@ class CacheGcCommand extends PubCommand {
       help: 'Also delete recent files',
       hideNegatedUsage: true,
     );
+    argParser.addFlag(
+      'dry-run',
+      help: 'Print list of files that would be deleted',
+      hideNegatedUsage: true,
+    );
   }
 
   @override
   Future<void> runProtected() async {
+    final dryRun = argResults.flag('dry-run');
     final activeRoots = cache.activeRoots();
     final validActiveRoots = <String>[];
     final paths = <String>{};
@@ -131,11 +137,17 @@ class CacheGcCommand extends PubCommand {
     log.message('');
     log.message(
       '''
-All other projects will need to run `$topLevelProgram pub get` again to work correctly.''',
+All other projects ${dryRun ? 'would' : 'will'} need to run `$topLevelProgram pub get` again to work correctly.''',
     );
-    log.message('Will recover ${readableFileSize(sum)}.');
-
-    if (argResults.flag('force') ||
+    log.message(
+      '${dryRun ? 'Would' : 'Will'} recover ${readableFileSize(sum)}.',
+    );
+    if (dryRun) {
+      log.message('Would delete:');
+      for (final path in allPathsToGC..sort()) {
+        log.message(path);
+      }
+    } else if (argResults.flag('force') ||
         await confirm('Are you sure you want to continue?')) {
       await log.progress('Deleting unused cache entries', () async {
         for (final path in allPathsToGC..sort()) {

test/cache/gc_test.dart

@@ -153,6 +153,22 @@ void main() async {
       output: allOf(matchesAppPath, contains('No unused cache entries found')),
     );
     final s = RegExp.escape(p.separator);
+    await runPub(
+      args: ['cache', 'gc', '--force', '--ignore-timestamp', '--dry-run'],
+      output: allOf([
+        matchesAppPath,
+        contains(RegExp('Would recover [0-9]{3} KB.')),
+        contains(RegExp('.*git.*cache${s}git1-.*')),
+        contains(RegExp('.*git.*cache${s}git_with_path1-.*')),
+        contains(RegExp('.*git.*git1-.*')),
+        contains(RegExp('.*git.*git_with_path1-.*')),
+        contains(RegExp('.*hosted-hashes.*hosted1-1.0.0.sha256')),
+        contains(RegExp('.*hosted.*hosted1-1.0.0.')),
+        isNot(contains(RegExp('.*hosted2'))),
+        isNot(contains(RegExp('.*git2'))),
+        isNot(contains(RegExp('.*git_with_path2'))),
+      ]),
+    );
     await runPub(
       args: ['cache', 'gc', '--force', '--ignore-timestamp'],
       output: allOf(
@@ -166,9 +182,7 @@ void main() async {
         ),
         contains(RegExp('Deleting directory .*git.*git1-.*')),
         contains(RegExp('Deleting directory .*git.*git_with_path1-.*')),
-        contains(
-          RegExp('Deleting file .*hosted-hashes.*hosted1-1.0.0.sha256.'),
-        ),
+        contains(RegExp('Deleting file .*hosted-hashes.*hosted1-1.0.0.sha256')),
         contains(RegExp('Deleting directory .*hosted.*hosted1-1.0.0.')),
         isNot(contains(RegExp('Deleting.*hosted2'))),
         isNot(contains(RegExp('Deleting.*git2'))),