Support defining environment constants for dart2js via the command-line.

sdk/lib/_internal/pub/lib/src/command/build.dart

Index: sdk/lib/_internal/pub/lib/src/command/build.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/build.dart b/sdk/lib/_internal/pub/lib/src/command/build.dart
index 1a88922c2fc695bd85274821596ada401681426a..b07cd95d617b7c054fd607f49dba7d198cf5dc3c 100644
--- a/sdk/lib/_internal/pub/lib/src/command/build.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/build.dart
@@ -35,6 +35,10 @@ class BuildCommand extends BarbackCommand {
   int builtFiles = 0;
 
   BuildCommand() {
+    argParser.addOption("define", abbr: "D",
+        help: "Defines an environment constant for dart2js.",
+        allowMultiple: true, splitCommas: false);

[Bob Nystrom, 2015/04/24 21:33:09]

Why make splitCommas false?

[nweiz, 2015/04/24 21:38:06]

Because there's nothing stopping environment constants from containing commas.
Also, it would be different from how dart2js handles it.

+
     argParser.addOption("format",
         help: "How output should be displayed.",
         allowed: ["text", "json"], defaultsTo: "text");
@@ -50,10 +54,16 @@ class BuildCommand extends BarbackCommand {
     var errorsJson = [];
     var logJson = [];
 
+    var environmentConstants = new Map.fromIterable(argResults["define"],
+        key: (pair) => pair.split("=").first,
+        value: (pair) => pair.split("=").last);
+
     // Since this server will only be hit by the transformer loader and isn't
     // user-facing, just use an IPv4 address to avoid a weird bug on the
     // OS X buildbots.
-    return AssetEnvironment.create(entrypoint, mode, useDart2JS: true)
+    return AssetEnvironment.create(entrypoint, mode,
+            environmentConstants: environmentConstants,
+            useDart2JS: true)
         .then((environment) {
       // Show in-progress errors, but not results. Those get handled
       // implicitly by getAllAssets().