improve error message when outpus are not disjoint

2 files changed, 6 insertions, 1 deletions

diff --git a/src/buildtool/build_engine/target_map/TARGETS b/src/buildtool/build_engine/target_map/TARGETS
index 9fb4df3a..2539aa59 100644
--- a/src/buildtool/build_engine/target_map/TARGETS
+++ b/src/buildtool/build_engine/target_map/TARGETS
@@ -49,7 +49,9 @@
     , ["src/buildtool/multithreading", "async_map_consumer"]
     , ["src/utils/cpp", "hash_combine"]
     , ["src/utils/cpp", "path"]
+    , ["@", "fmt", "", "fmt"]
     , ["@", "gsl-lite", "", "gsl-lite"]
+    , ["@", "json", "", "json"]
     ]
   , "stage": ["src", "buildtool", "build_engine", "target_map"]
   }
diff --git a/src/buildtool/build_engine/target_map/target_map.cpp b/src/buildtool/build_engine/target_map/target_map.cpp
index 4f32cdf1..815f1432 100644
--- a/src/buildtool/build_engine/target_map/target_map.cpp
+++ b/src/buildtool/build_engine/target_map/target_map.cpp
@@ -6,6 +6,7 @@
 #include <string>
 #include <utility>
 
+#include "fmt/format.h"
 #include "nlohmann/json.hpp"
 #include "src/buildtool/build_engine/base_maps/field_reader.hpp"
 #include "src/buildtool/build_engine/expression/configuration.hpp"
@@ -405,7 +406,9 @@ void withDependencies(
                                     std::back_inserter(dups));
               if (not dups.empty()) {
                   throw Evaluator::EvaluationError{
-                      "outs and out_dirs for ACTION must be disjoint"};
+                      fmt::format("outs and out_dirs for ACTION must be "
+                                  "disjoint. Found repeated entries:\n{}",
+                                  nlohmann::json(dups).dump())};
               }
 
               std::vector<std::string> cmd;