Remove phony edges for nodes created by a dependency loader.

This patch simplifies Ninja internals without modifying
its behavior. It removes the creation (and removal) of phony
edges as producers for nodes loaded by dependency loaders, i.e.
coming from depfiles, dyndep files or the deps log.

These edges were only used to ensure the build did not
abort when these files are missing, unlike regular source
inputs. This can be easily checked by adding a new flag to
the Node class instead. This makes it easier to reason about
how Ninja works internally.

More specifically:

- Move the generated_by_dep_loader_ flag from the Edge class
  to the Node class. The flag is true by default to minimize
  changes to the source code, since node instances can be
  first created by reading the deps or build logs before
  the manifest itself.

- Modify Plan::AddSubTarget() to avoid aborting the build
  when a generated-by-deploader node is missing. Instead
  the function exits immediately, which corresponds to
  what happened before.

- State::AddOut(), State::AddIn(), State::AddValidation():
  Ensure that nodes added by these methods, which are
  only called from the manifest parser and unit-tests
  set the |generated_by_dep_loader_| flag to false, to
  indicate that these are regular input / output nodes.

- ManifestParser::ParseEdge(): Add an assertion verifying
  that the dyndep file is marked as a regular input.

- DyndepLoader::UpdateEdge(): Remove code path that
  looked for phony in-edges and ignored them.

- DepLoader::CreatePhonyInEdge() is removed as no
  longer necessary.

+ Update a few places in unit-tests that were checking
  for the creation of the phony edges.

Fuchsia-Topic: persistent-mode
Change-Id: I98998238002351ef9c7a103040eb8a26d4183969

1 files changed, 3 insertions, 0 deletions

diff --git a/src/state.h b/src/state.h
index 878ac6d..886b78f 100644
--- a/src/state.h
+++ b/src/state.h
@@ -105,6 +105,9 @@ struct State {
   Node* LookupNode(StringPiece path) const;
   Node* SpellcheckNode(const std::string& path);
 
+  /// Add input / output / validation nodes to a given edge. This also
+  /// ensures that the generated_by_dep_loader() flag for all these nodes
+  /// is set to false, to indicate that they come from the input manifest.
   void AddIn(Edge* edge, StringPiece path, uint64_t slash_bits);
   bool AddOut(Edge* edge, StringPiece path, uint64_t slash_bits);
   void AddValidation(Edge* edge, StringPiece path, uint64_t slash_bits);