Add import dependencies to Kernel libraries and use them to resynthesize ImportElement(s) in Analyz…

pkg/kernel/lib/text/ast_to_text.dart

 // Copyright (c) 2016, 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.
 library kernel.ast_to_text;
 
 import '../ast.dart';
 import '../import_table.dart';
 
 class Namer<T> {
   int index = 0;
@@ skipping 265 matching lines @@
       var importPath = imports.getImportPath(library);
       if (importPath == "") {
         var prefix =
             syntheticNames.nameLibraryPrefix(library, proposedName: 'self');
         endLine('import self as $prefix;');
       } else {
         var prefix = syntheticNames.nameLibraryPrefix(library);
         endLine('import "$importPath" as $prefix;');
       }
     }
-    for (var import in library.dependencies) {

[Siggi Cherem (dart-lang), 2017/07/20 18:29:00]

I'm not sure I understand this part of the change. This means we no longer print
out library dependencies? Is this to avoid changes to the expectation files in
our unit tests?

If so, I would prefer not to make this change here, but update the expectations
or make a change that doesn't affect regular printing but affects printing of
external libraries only?

[scheglov, 2017/07/20 19:33:53]

First of all, this code has not been used, because we used not to add
dependencies to libraries when building them. Instead, the code about uses
LibraryImportTable to gather "actually used" imports and generate synthetic
prefixes assigned to them, and then we print only these "actually used" imports
into text presentation.

I agree that if we want to have our tests validate that we add required
import/export dependencies into kernels as we build them, we need to update all
the expectations. One nasty consequence of this would be that we will have
duplicate sets of imports - one for "actually used" and another for "specified".
If that's what you think is OK, then I can update all expectations.

[Siggi Cherem (dart-lang), 2017/07/20 22:50:36]

Thanks so much for the clarification. Given your explanation, I'm OK submitting
this change as it is. Let's write a TODO and open a bug to follow up with the
kernel-team on this issue. It seems low priority, but they can let us know if
they have any concerns.

[scheglov, 2017/07/21 16:21:33]

I will add TODO, https://github.com/dart-lang/sdk/issues/30224

-      import.accept(this);
-    }
     endLine();
     var inner = new Printer._inner(this, imports);
-    library.dependencies.forEach(inner.writeNode);
     library.typedefs.forEach(inner.writeNode);
     library.classes.forEach(inner.writeNode);
     library.fields.forEach(inner.writeNode);
     library.procedures.forEach(inner.writeNode);
   }
 
   void writeProgramFile(Program program) {
     ImportTable imports = new ProgramImportTable(program);
     var inner = new Printer._inner(this, imports);
     writeWord('main');
@@ skipping 1369 matching lines @@
   }
   throw 'illegal ProcedureKind: $kind';
 }
 
 class ExpressionPrinter {
   final Printer writeer;
   final int minimumPrecedence;
 
   ExpressionPrinter(this.writeer, this.minimumPrecedence);
 }