move extractDefinedVariables from analyzer cli to analyzer

pkg/analyzer/lib/src/command_line/arguments.dart

Index: pkg/analyzer/lib/src/command_line/arguments.dart
diff --git a/pkg/analyzer/lib/src/command_line/arguments.dart b/pkg/analyzer/lib/src/command_line/arguments.dart
index 9b6e9f81f69d57a9fed1a88de6fd72d9f490739c..941075f21217cc2f63f2cd5ca3ebe61686424306 100644
--- a/pkg/analyzer/lib/src/command_line/arguments.dart
+++ b/pkg/analyzer/lib/src/command_line/arguments.dart
@@ -165,6 +165,35 @@ void defineAnalysisArguments(ArgParser parser) {
 }
 
 /**
+ * Find arguments of the form -Dkey=value
+ * or argument pairs of the form -Dkey value
+ * and place those key/value pairs into [definedVariables].
+ * Return a list of arguments with the key/value arguments removed.
+ */
+List<String> extractDefinedVariables(

[Brian Wilkerson, 2016/12/14 17:47:35]

This is already being done as part of createContextBuilderOptions. Given that we
want to move everyone to using ContextBuilder, we could just build the options,
and extract the declared variables for now knowing that this gets us closer to
the longer term goal.

[danrubel, 2016/12/14 18:06:56]

That makes sense as a long term goal, but I'd like to take it in smaller steps.
I tried to be more ambitious last week and didn't make any progress. I found
that detangling and normalizing Analyzer CLI and DDC code to be more involved
than I thought. This week I'm taking it in smaller steps and making good
progress. Ok if I check this in as a step towards what you describe?

+    List<String> args, Map<String, String> definedVariables) {
+  int count = args.length;
+  List<String> remainingArgs = <String>[];
+  for (int i = 0; i < count; i++) {
+    String arg = args[i];
+    if (arg == '--') {
+      while (i < count) {
+        remainingArgs.add(args[i++]);
+      }
+    } else if (arg.startsWith("-D")) {
+      if (i + 1 < count) {
+        definedVariables[arg.substring(2)] = args[++i];
+      } else {
+        remainingArgs.add(arg);
+      }
+    } else {
+      remainingArgs.add(arg);
+    }
+  }
+  return remainingArgs;
+}
+
+/**
  * Return a list of command-line arguments containing all of the given [args]
  * that are defined by the given [parser]. An argument is considered to be
  * defined by the parser if