Validate packages against their SDK constraints.

utils/pub/entrypoint.dart

Index: utils/pub/entrypoint.dart
diff --git a/utils/pub/entrypoint.dart b/utils/pub/entrypoint.dart
index 30bfeb1650a37f6af89274ae9180f255b30578eb..9a68c12e7bf7f299aed2d3fd46bf5be066bc836c 100644
--- a/utils/pub/entrypoint.dart
+++ b/utils/pub/entrypoint.dart
@@ -9,6 +9,7 @@ import 'io.dart';
 import 'lock_file.dart';
 import 'log.dart' as log;
 import 'package.dart';
+import 'sdk.dart' as sdk;
 import 'system_cache.dart';
 import 'utils.dart';
 import 'version.dart';
@@ -139,6 +140,62 @@ class Entrypoint {
       .then(_linkSecondaryPackageDirs);
   }
 
+  /// Traverses the root's package dependency graph and loads each of the
+  /// reached packages. This should only be called after the lockfile has been
+  /// successfully generated.
+  Future<List<Package>> walkDependencies() {

[nweiz, 2013/01/31 22:38:53]

Maybe this and validateSdkConstraints should be methods on LockFile? It weirds
me out that they have this weird "should only be called" requirement.

[Bob Nystrom, 2013/02/01 16:53:29]

I put it here because walking the locked transitive deps is really only
meaningful for the root package. Seemed like it made sense here. LockFile is
really just the state for the file itself and not the root package that owns it.
Yeah, I'm not crazy about that either. Before when this was a separate command,
it would throw an error if an entry wasn't in the lock file. For now, I think
the comment is enough?

[nweiz, 2013/02/01 22:24:54]

I'd like to at least get an exception if this is called incorrectly. Right now
it'll just use an empty lockfile and return [].

[Bob Nystrom, 2013/02/02 00:02:31]

It should fail if called with an out of date lockfile. It will try to look up a
dependency in it and get null back and then barf on that.

+    return loadLockFile().then((lockFile) {
+      var group = new FutureGroup<Package>();
+      var visited = new Set<String>();
+
+      // Include the root package in the results.
+      group.add(new Future.immediate(root));
+
+      visitPackage(Package package) {
+        for (var ref in package.dependencies) {
+          if (visited.contains(ref.name)) continue;
+
+          // Look up the concrete version.
+          var id = lockFile.packages[ref.name];
+
+          visited.add(ref.name);
+          var future = cache.describe(id);
+          group.add(future.then(visitPackage));
+        }
+
+        return package;
+      }
+
+      visitPackage(root);
+      return group.future;
+    });
+  }
+
+  /// Validates that the current Dart SDK version matches the SDK constraints
+  /// of every package in the dependency graph. If a package's constraint does
+  /// not match, prints an error.
+  Future validateSdkConstraints() {
+    return walkDependencies().then((packages) {
+      var errors = [];
+
+      for (var package in packages) {
+        var sdkConstraint = package.pubspec.environment.sdkVersion;
+        if (!sdkConstraint.allows(sdk.version)) {
+          errors.add("- '${package.name}' requires ${sdkConstraint}");
+        }
+      }
+
+      if (errors.length > 0) {
+        log.error("Some packages are not compatible with SDK version "
+            "${sdk.version}:\n${errors.join('\n')}\n\n"

[nweiz, 2013/01/31 22:38:53]

When I'm formatting multiline strings like this, I usually add an additional
four spaces of indentation when there's a line break in the source but no line
break in the output. I'd also probably add a source newline after the first
"\n". For example:

    log.error("Some packages are not compatible with SDK version "
            "${sdk.version}:\n"
        "${errors.join('\n')}\n\n"
        "You may be able to resolve this by upgrading to the latest Dart "
            "SDK\n"
        "or adding a version constraint to use an older version of a "
            "package.");

Also, maybe "with SDK version" -> "with your SDK version".

[Bob Nystrom, 2013/02/01 16:53:29]

Done and done.

+            "You may be able to resolve this by upgrading to the latest Dart "
+            "SDK\n"
+            "or adding a version constraint to use an older version of a "
+            "package.");
+      }
+    });
+  }
+
   /// Loads the list of concrete package versions from the `pubspec.lock`, if it
   /// exists. If it doesn't, this completes to an empty [LockFile].
   Future<LockFile> loadLockFile() {