Add simple test migration helper.

tools/migration/bin/migrate_batch.dart

Index: tools/migration/bin/migrate_batch.dart
diff --git a/tools/migration/bin/migrate_batch.dart b/tools/migration/bin/migrate_batch.dart
new file mode 100644
index 0000000000000000000000000000000000000000..b0ae2b1f2722a5cf9940da0314a11dc39df77ed4
--- /dev/null
+++ b/tools/migration/bin/migrate_batch.dart
@@ -0,0 +1,290 @@
+// Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// Given the beginning and ending file names in a batch, does as much automated
+/// migration and possible and prints out the remaining manual steps required.
+///
+/// This should be safe to run, and safe to re-run on an in-progress chunk.
+/// However, it has not been thoroughly tested, so run at your own risk.
+
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+
+import 'package:migration/src/log.dart';
+
+const simpleDirs = const ["corelib", "language", "lib"];
+
+final String sdkRoot =
+    p.normalize(p.join(p.dirname(p.fromUri(Platform.script)), '../../../'));
+
+final String testRoot = p.join(sdkRoot, "tests");
+
+bool dryRun = false;
+
+void main(List<String> arguments) {
+  if (arguments.contains("--dry-run")) {
+    dryRun = true;
+    arguments = arguments.where((argument) => argument != "--dry-run").toList();
+  }
+
+  if (arguments.length != 2) {
+    stderr.writeln(
+        "Usage: dart migrate_batch.dart [--dry-run] <first file> <last file>");
+    stderr.writeln();
+    stderr.writeln("Example:");
+    stderr.writeln();
+    stderr.writeln(
+        "    \$ dart migrate_batch.dart corelib/map_to_string corelib/queue");
+    exit(1);
+  }
+
+  var first = toTwoPath(arguments[0]);
+  var last = toTwoPath(arguments[1]);
+
+  var tests = scanTests();
+
+  // Find the range of files in the chunk. We use comparisons here instead of
+  // equality to try to compensate for files that may only appear in one fork
+  // and should be part of the chunk but aren't officially listed as the begin
+  // or end point.
+  var startIndex = -1;
+  var endIndex = 0;
+  for (var i = 0; i < tests.length; i++) {
+    if (startIndex == -1 && tests[i].twoPath.compareTo(first) >= 0) {
+      startIndex = i;
+    }
+
+    if (tests[i].twoPath.compareTo(last) > 0) {
+      endIndex = i;
+      break;
+    }
+  }
+
+  print("Migrating ${bold(endIndex - startIndex)} tests from ${bold(first)} "
+      "to ${bold(last)}...");
+  print("");
+
+  var todos = <String>[];
+  var migratedTests = 0;
+  var unmigratedTests = 0;
+  for (var i = startIndex; i < endIndex; i++) {
+    if (tests[i].migrate(todos)) {
+      migratedTests++;
+    } else {
+      unmigratedTests++;
+    }
+  }
+
+  print("");
+
+  var summary = "";
+
+  if (migratedTests > 0) {
+    var s = migratedTests == 1 ? "" : "s";
+    summary += "Successfully migrated ${green(migratedTests)} test$s. ";
+  }
+
+  if (unmigratedTests > 0) {
+    var s = migratedTests == 1 ? "" : "s";
+    summary += "Need manual work on ${red(unmigratedTests)} test$s:";
+  }
+
+  print(summary);
+  todos.forEach(todo);
+}
+
+String toTwoPath(String path) {
+  // Allow eliding "_test" and/or ".dart" to make things more command-line
+  // friendly.
+  if (!path.endsWith("_test.dart")) path += "_test.dart";
+  if (!path.endsWith(".dart")) path += ".dart";
+
+  for (var dir in simpleDirs) {
+    if (p.isWithin(dir, path)) {
+      return p.join("${dir}_2", p.relative(path, from: dir));
+    }
+
+    if (p.isWithin("${dir}_strong", path)) {
+      return p.join("${dir}_2", p.relative(path, from: dir));
+    }
+  }
+
+  if (p.isWithin("html", path)) {
+    return p.join("lib_2/html", p.relative(path, from: "html"));
+  }
+
+  if (p.isWithin("isolate", path)) {
+    return p.join("lib_2/isolate", p.relative(path, from: "isolate"));
+  }
+
+  // Guess it's already a two path.
+  return path;
+}
+
+/// Loads all of the unforked test files.
+///
+/// Creates an list of [Fork]s, ordered by their destination paths. Handles
+/// tests that only appear in one fork or the other, or both.
+List<Fork> scanTests() {
+  var tests = <String, Fork>{};
+
+  addTestDirectory(String fromDir, String twoDir) {
+    for (var entry
+        in new Directory(p.join(testRoot, fromDir)).listSync(recursive: true)) {
+      if (!entry.path.endsWith("_test.dart")) continue;
+
+      var fromPath = p.relative(entry.path, from: testRoot);
+      var twoPath = p.join(twoDir, p.relative(fromPath, from: fromDir));
+
+      var fork = tests.putIfAbsent(twoPath, () => new Fork(twoPath));
+      if (fromDir.contains("_strong")) {
+        fork.strongPath = fromPath;
+      } else {
+        fork.onePath = fromPath;
+      }
+    }
+  }
+
+  addTestDirectory("corelib", "corelib_2");
+  addTestDirectory("corelib_strong", "corelib_2");
+  addTestDirectory("html", "lib_2/html");
+  addTestDirectory("isolate", "lib_2/isolate");
+  addTestDirectory("language", "language_2");
+  addTestDirectory("language_strong", "language_2");
+  addTestDirectory("lib", "lib_2");
+  addTestDirectory("lib_strong", "lib_2");
+
+  var sorted = tests.values.toList();
+  sorted.sort((a, b) => a.twoPath.compareTo(b.twoPath));
+  return sorted;
+}
+
+/// Moves the file from [from] to [to], which are both assumed to be relative
+/// paths inside "tests".
+void moveFile(String from, String to) {
+  if (dryRun) {
+    print("  Dry run: move $from to $to");
+    return;
+  }
+
+  new File(p.join(testRoot, from)).renameSync(p.join(testRoot, to));
+}
+
+/// Reads the contents of the file at [path], which is assumed to be relative
+/// within "tests".
+String readFile(String path) {
+  return new File(p.join(testRoot, path)).readAsStringSync();
+}
+
+/// Deletes the file at [path], which is assumed to be relative within "tests".
+void deleteFile(String path) {
+  if (dryRun) {
+    print("  Dry run: delete $path");
+    return;
+  }
+
+  new File(p.join(testRoot, path)).deleteSync();
+}
+
+bool checkForUnitTest(String path, String source) {
+  if (!source.contains("package:unittest")) return false;
+
+  note("${bold(path)} uses unittest package.");
+  return true;
+}
+
+class Fork {
+  final String twoPath;
+  String onePath;
+  String strongPath;
+
+  String get twoSource {
+    if (twoPath == null) return null;
+    if (_twoSource == null) _twoSource = readFile(twoPath);
+    return _twoSource;
+  }
+
+  String _twoSource;
+
+  String get oneSource {
+    if (onePath == null) return null;
+    if (_oneSource == null) _oneSource = readFile(onePath);
+    return _oneSource;
+  }
+
+  String _oneSource;
+
+  String get strongSource {
+    if (strongPath == null) return null;
+    if (_strongSource == null) _strongSource = readFile(strongPath);
+    return _strongSource;
+  }
+
+  String _strongSource;
+
+  Fork(this.twoPath);
+
+  bool migrate(List<String> todos) {
+    print("- ${bold(twoPath)}:");
+
+    var todosBefore = todos.length;
+    var isMigrated = new File(p.join(testRoot, twoPath)).existsSync();
+
+    // If there is a migrated version and it's the same as an unmigrated one,
+    // delete the unmigrated one.
+    if (isMigrated) {
+      if (onePath != null) {
+        if (oneSource == twoSource) {
+          deleteFile(onePath);
+          done("Deleted already-migrated $onePath.");
+        } else {
+          note("${bold(onePath)} does not match already-migrated "
+              "${bold(twoPath)}.");
+          todos.add("Merge ${bold(onePath)} into ${bold(twoPath)}.");
+          checkForUnitTest(onePath, oneSource);
+        }
+      }
+
+      if (strongPath != null) {
+        if (strongSource == twoSource) {
+          deleteFile(strongPath);
+          done("Deleted already-migrated ${bold(strongPath)}.");
+        } else {
+          note("${bold(strongPath)} does not match already-migrated "
+              "${bold(twoPath)}.");
+          todos.add("Merge ${bold(strongPath)} into ${bold(twoPath)}.");
+          checkForUnitTest(strongPath, strongSource);
+        }
+      }
+    } else {
+      // If it only exists in one place, just move it.
+      if (strongPath == null) {
+        moveFile(onePath, twoPath);
+        done("Moved from ${bold(onePath)} (no strong mode fork).");
+      } else if (onePath == null) {
+        moveFile(strongPath, twoPath);
+        done("Moved from ${bold(strongPath)} (no 1.0 mode fork).");
+      } else if (oneSource == strongSource) {
+        // The forks are identical, pick one.
+        moveFile(onePath, twoPath);
+        deleteFile(strongPath);
+        done("Merged identical forks.");
+        checkForUnitTest(twoPath, oneSource);
+      } else {
+        // Otherwise, a manual merge is required. Start with the strong one.
+        moveFile(strongPath, twoPath);
+        done("Moved strong fork, kept 1.0 fork, manual merge required.");
+        todos.add("Merge ${bold(onePath)} into ${bold(twoPath)}.");
+        checkForUnitTest(onePath, oneSource);
+      }
+    }
+
+    if (checkForUnitTest(twoPath, twoSource)) {
+      todos.add("Migrate ${bold(twoPath)} off unittest.");
+    }
+
+    return todos.length == todosBefore;
+  }
+}