Parser accepts no explicit outputs.

There is a class of commands that take an output directory where
they create their output files. Among them are cp(1), tar(1) to name a
few. These commands have one or more implicit outputs but no explicit
output.

With this patch, Ninja's parser accepts build edge with an
empty list of explicit outputs.

Author: nicolasdespres

src/graph_test.cc

@@ -149,6 +149,45 @@ TEST_F(GraphTest, ImplicitOutputOutOfDate) {
   EXPECT_TRUE(GetNode("out.imp")->dirty());
 }
 
+TEST_F(GraphTest, ImplicitOutputOnlyParse) {
+  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
+"build | out.imp: cat in\n"));
+
+  Edge* edge = GetNode("out.imp")->in_edge();
+  EXPECT_EQ(1, edge->outputs_.size());
+  EXPECT_EQ("out.imp", edge->outputs_[0]->path());
+  EXPECT_EQ(1, edge->implicit_outs_);
+  EXPECT_EQ(edge, GetNode("out.imp")->in_edge());
+}
+
+TEST_F(GraphTest, ImplicitOutputOnlyMissing) {
+  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
+"build | out.imp: cat in\n"));
+  fs_.Create("in", "");
+
+  Edge* edge = GetNode("out.imp")->in_edge();
+  string err;
+  EXPECT_TRUE(scan_.RecomputeDirty(edge, &err));
+  ASSERT_EQ("", err);
+
+  EXPECT_TRUE(GetNode("out.imp")->dirty());
+}
+
+TEST_F(GraphTest, ImplicitOutputOnlyOutOfDate) {
+  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
+"build | out.imp: cat in\n"));
+  fs_.Create("out.imp", "");
+  fs_.Tick();
+  fs_.Create("in", "");
+
+  Edge* edge = GetNode("out.imp")->in_edge();
+  string err;
+  EXPECT_TRUE(scan_.RecomputeDirty(edge, &err));
+  ASSERT_EQ("", err);
+
+  EXPECT_TRUE(GetNode("out.imp")->dirty());
+}
+
 TEST_F(GraphTest, PathWithCurrentDirectory) {
   ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
 "rule catdep\n"

src/manifest_parser.cc

@@ -236,16 +236,13 @@ bool ManifestParser::ParseEdge(string* err) {
     EvalString out;
     if (!lexer_.ReadPath(&out, err))
       return false;
-    if (out.empty())
-      return lexer_.Error("expected path", err);
-
-    do {
+    while (!out.empty()) {
       outs.push_back(out);
 
       out.Clear();
       if (!lexer_.ReadPath(&out, err))
         return false;
-    } while (!out.empty());
+    }
   }
 
   // Add all implicit outs, counting how many as we go.
@@ -262,6 +259,9 @@ bool ManifestParser::ParseEdge(string* err) {
     }
   }
 
+  if (outs.empty())
+    return lexer_.Error("expected path", err);
+
   if (!ExpectToken(Lexer::COLON, err))
     return false;
 

src/manifest_parser_test.cc

@@ -976,13 +976,10 @@ TEST_F(ParserTest, ImplicitOutputDupes) {
 TEST_F(ParserTest, NoExplicitOutput) {
   ManifestParser parser(&state, NULL, kDupeEdgeActionWarn);
   string err;
-  EXPECT_FALSE(parser.ParseTest(
+  EXPECT_TRUE(parser.ParseTest(
 "rule cat\n"
 "  command = cat $in > $out\n"
 "build | imp : cat bar\n", &err));
-  ASSERT_EQ("input:3: expected path\n"
-            "build | imp : cat bar\n"
-            "      ^ near here", err);
 }
 
 TEST_F(ParserTest, DefaultDefault) {