Dyndep‑listed implicit dependencies are no longer silently ignored when missing.

Ninja now reports an error if a dyndep input is missing and has no rule to build it,
except when the node is also marked as depfile‑loaded, in which case the check is suppressed.

Author: moritzx22

src/build.cc

@@ -825,6 +825,17 @@ bool Builder::StartEdge(Edge* edge, string* err) {
   if (edge->is_phony())
     return true;
 
+  // Late validation: verify that dyndep‑only inputs are present.
+  for (const auto input : edge->inputs_) {
+    if (input->missing() && input->generated_by_dyndep_loader()) {
+      string referenced;
+      referenced = ", needed by dyndep '" + edge->GetUnescapedDyndep() + "',";
+      *err = "'" + input->path() + "'" + referenced +
+             " missing and no known rule to make it";
+      return false;
+    }
+  }
+
   int64_t start_time_millis = GetTimeMillis() - start_time_millis_;
   running_edges_.insert(make_pair(edge, start_time_millis));
 
@@ -943,6 +954,13 @@ bool Builder::FinishCommand(CommandRunner::Result* result, string* err) {
         }
       }
     }
+
+    // Refresh output file status to support later dyndep existence checks.
+    // https://github.com/ninja-build/ninja/issues/2573
+    for (auto o : edge->outputs_) {
+      o->MarkExists();
+    }
+
     if (node_cleaned) {
       record_mtime = edge->command_start_time_;
     }

src/build_test.cc

@@ -3367,6 +3367,61 @@ TEST_F(BuildTest, DyndepMissingAndNoRule) {
   EXPECT_EQ("loading 'dd': No such file or directory", err);
 }
 
+TEST_F(BuildTest, DyndepMissingInput) {
+  // Check that the build system detects when a dyndep-provided input is missing
+  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
+                                      R"ninja(
+rule touch
+  command = touch $out $out.imp
+build out: touch || dd
+  dyndep = dd
+)ninja"));
+
+  fs_.Create("dd", R"ninja(
+ninja_dyndep_version = 1
+build out | out.imp: dyndep | tmp.imp missing.imp
+)ninja");
+
+  fs_.Create("tmp.imp", "");
+
+  string err;
+  EXPECT_TRUE(builder_.AddTarget("out", &err));
+  ASSERT_EQ("", err);
+  EXPECT_EQ(builder_.Build(&err), ExitFailure);
+  EXPECT_EQ("'missing.imp', needed by dyndep 'dd', missing and no known rule to make it", err);
+  EXPECT_TRUE(command_runner_.commands_ran_.empty());
+}
+
+TEST_F(BuildTest, DyndepMissingInputUsedInDepFile) {
+  // The missing input cannot be detected because the dyndep‑introduced node is
+  // also marked as coming from a depfile.
+  ASSERT_NO_FATAL_FAILURE(AssertParse(&state_,
+                                      R"ninja(
+rule touch
+  command = touch $out $out.imp
+build out2: touch out1 || dd
+  dyndep = dd
+build out1: touch
+  depfile = out2.d
+)ninja"));
+
+  fs_.Create("dd", R"ninja(
+ninja_dyndep_version = 1
+build out2 | out2.imp: dyndep | tmp.imp missing.imp
+)ninja");
+  fs_.Create("out2.d", "out1: missing.imp\n");
+  fs_.Create("tmp.imp", "");
+
+  string err;
+  EXPECT_TRUE(builder_.AddTarget("out2", &err));
+  ASSERT_EQ("", err);
+  EXPECT_EQ(builder_.Build(&err), ExitSuccess);
+  EXPECT_EQ("", err);
+  ASSERT_EQ(2u, command_runner_.commands_ran_.size());
+  EXPECT_EQ("touch out1 out1.imp", command_runner_.commands_ran_[0]);
+  EXPECT_EQ("touch out2 out2.imp", command_runner_.commands_ran_[1]);
+}
+
 TEST_F(BuildTest, DyndepReadyImplicitConnection) {
   // Verify that a dyndep file can be loaded immediately to discover
   // that one edge has an implicit output that is also an implicit

src/graph.h

@@ -77,6 +77,14 @@ struct Node {
     return exists_ == ExistenceStatusExists;
   }
 
+  void MarkExists() {
+    exists_ = ExistenceStatusExists;
+  }
+
+  bool missing() const {
+    return exists_ == ExistenceStatusMissing;
+  }
+
   bool status_known() const {
     return exists_ != ExistenceStatusUnknown;
   }