Restore tolerance of self-referencing phony build statements

Since commit v1.8.0^2~3^2~1 (Teach RecomputeDirty to detect cycles in
the build graph, 2015-11-13) we correctly reject self-referencing phony
build statements like

    build a: phony a

as cycles.  Unfortunately this breaks support for CMake 2.8.12.x and
3.0.x because those versions incorrectly produce edges of this form
(that we used to tolerate).  In order to preserve compatibility with
those CMake versions we need to restore tolerance of these edges.

Add a special case to the manifest parser to filter out self-referencing
inputs of phony edges of the form produced by those CMake versions.
Warn by default, but add a `-w phonycycle={err,warn}` option to make it
an error.

Fixes: #1322

1 files changed, 16 insertions, 2 deletions

diff --git a/src/ninja.cc b/src/ninja.cc
index 586e8dc..ed004ac 100644
--- a/src/ninja.cc
+++ b/src/ninja.cc
@@ -70,6 +70,9 @@ struct Options {
 
   /// Whether duplicate rules for one target should warn or print an error.
   bool dupe_edges_should_err;
+
+  /// Whether phony cycles should warn or print an error.
+  bool phony_cycle_should_err;
 };
 
 /// The Ninja main() loads up a series of data structures; various tools need
@@ -845,7 +848,8 @@ bool DebugEnable(const string& name) {
 bool WarningEnable(const string& name, Options* options) {
   if (name == "list") {
     printf("warning flags:\n"
-"  dupbuild={err,warn}  multiple build lines for one target\n");
+"  dupbuild={err,warn}  multiple build lines for one target\n"
+"  phonycycle={err,warn}  phony build statement references itself\n");
     return false;
   } else if (name == "dupbuild=err") {
     options->dupe_edges_should_err = true;
@@ -853,9 +857,16 @@ bool WarningEnable(const string& name, Options* options) {
   } else if (name == "dupbuild=warn") {
     options->dupe_edges_should_err = false;
     return true;
+  } else if (name == "phonycycle=err") {
+    options->phony_cycle_should_err = true;
+    return true;
+  } else if (name == "phonycycle=warn") {
+    options->phony_cycle_should_err = false;
+    return true;
   } else {
     const char* suggestion =
-        SpellcheckString(name.c_str(), "dupbuild=err", "dupbuild=warn", NULL);
+        SpellcheckString(name.c_str(), "dupbuild=err", "dupbuild=warn",
+                         "phonycycle=err", "phonycycle=warn", NULL);
     if (suggestion) {
       Error("unknown warning flag '%s', did you mean '%s'?",
             name.c_str(), suggestion);
@@ -1148,6 +1159,9 @@ int real_main(int argc, char** argv) {
     if (options.dupe_edges_should_err) {
       parser_opts.dupe_edge_action_ = kDupeEdgeActionError;
     }
+    if (options.phony_cycle_should_err) {
+      parser_opts.phony_cycle_action_ = kPhonyCycleActionError;
+    }
     ManifestParser parser(&ninja.state_, &ninja.disk_interface_, parser_opts);
     string err;
     if (!parser.Load(options.input_file, &err)) {