support part file completions

pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart

Index: pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart b/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
index 5426d294ad60a3b8deefd78f3bc2b8e9779ef4d0..5d743f4ce9864db4437fc9a585b09639662b4f44 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart_completion_manager.dart
@@ -79,7 +79,7 @@ class DartCompletionManager extends CompletionManager {
   Future<bool> computeCache() {
     return waitForAnalysis().then((CompilationUnit unit) {
       if (unit != null && !cache.isImportInfoCached(unit)) {
-        return cache.computeImportInfo(unit, searchEngine);
+        return cache.computeImportInfo(unit, searchEngine, true);
       } else {
         return new Future.value(false);
       }
@@ -189,9 +189,16 @@ class DartCompletionManager extends CompletionManager {
    * compilation unit is never going to be resolved.
    */
   Future<CompilationUnit> waitForAnalysis() {
+    List<Source> libraries = context.getLibrariesContaining(source);
+    assert(libraries != null);

[Paul Berry, 2014/12/19 19:13:30]

Nit pick: the change you've made adds assertions, which is great.  But it drops
the defensive programming, because it means that when the code is run in
unchecked mode, the presence of null will cause an exception.

IMHO it's best to be defensive for the benefit of unchecked mode and use
assertions for the benefit of checked mode.  For example, instead of doing the
rewrite you've done in this patch set, you could go back to what you had in
patch set 1 and just add a single assert statement:

if (libraries == null || libraries.length == 0 || libraries[0] == null) {
  // Only libraries.length == 0 is expected to occur in practice;
  // the others are to avoid NRE's.
  assert(libraries != null && libraries.length == 0);
  return new Future.value(null);
}

Your call, though.

+    if (libraries.length == 0) {
+      return new Future.value(null);
+    }
+    Source libSource = libraries[0];
+    assert(libSource != null);
     return context.computeResolvedCompilationUnitAsync(
         source,
-        source).catchError((_) {
+        libSource).catchError((_) {
       // This source file is not scheduled for analysis, so a resolved
       // compilation unit is never going to get computed.
       return null;