message: fix(compiler-cli): avoid producing source mappings for host views
  The host view doesn't map back to user code so the template compiler
  produces a blank `url` for them.
  PR Close
diff: @@ -144,6 +144,7 @@ class _NodeEmitterVisitor implements StatementVisitor, ExpressionVisitor {
  const span = node.sourceSpan;
  if (span.start.file == span.end.file) {
  const file = span.start.file;
  + if (file.url) {
  let source = this._templateSources.get(file);
  if (!source) {
  source = ts.createSourceMapSource(file.url, file.content, pos => pos);
  @@ -152,6 +153,7 @@ class _NodeEmitterVisitor implements StatementVisitor, ExpressionVisitor {
  return {pos: span.start.offset, end: span.end.offset, source};
  }
  }
  + }
  return null;
  }
  