Merge pull request #7788 from bobvanderlinden/pr-improve-nix-profile-install-error

Improve error on conflict for nix profile install

1 files changed, 57 insertions, 1 deletions

diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index 208542a5c..711fbe2f0 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -330,7 +330,63 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
             manifest.elements.push_back(std::move(element));
         }
 
-        updateProfile(manifest.build(store));
+        try {
+            updateProfile(manifest.build(store));
+        } catch (BuildEnvFileConflictError & conflictError) {
+            // FIXME use C++20 std::ranges once macOS has it
+            //       See https://github.com/NixOS/nix/compare/3efa476c5439f8f6c1968a6ba20a31d1239c2f04..1fe5d172ece51a619e879c4b86f603d9495cc102
+            auto findRefByFilePath = [&]<typename Iterator>(Iterator begin, Iterator end) {
+                for (auto it = begin; it != end; it++) {
+                    auto profileElement = *it;
+                    for (auto & storePath : profileElement.storePaths) {
+                        if (conflictError.fileA.starts_with(store->printStorePath(storePath))) {
+                            return std::pair(conflictError.fileA, profileElement.source->originalRef);
+                        }
+                        if (conflictError.fileB.starts_with(store->printStorePath(storePath))) {
+                            return std::pair(conflictError.fileB, profileElement.source->originalRef);
+                        }
+                    }
+                }
+                throw conflictError;
+            };
+            // There are 2 conflicting files. We need to find out which one is from the already installed package and
+            // which one is the package that is the new package that is being installed.
+            // The first matching package is the one that was already installed (original).
+            auto [originalConflictingFilePath, originalConflictingRef] = findRefByFilePath(manifest.elements.begin(), manifest.elements.end());
+            // The last matching package is the one that was going to be installed (new).
+            auto [newConflictingFilePath, newConflictingRef] = findRefByFilePath(manifest.elements.rbegin(), manifest.elements.rend());
+
+            throw Error(
+                "An existing package already provides the following file:\n"
+                "\n"
+                "  %1%\n"
+                "\n"
+                "This is the conflicting file from the new package:\n"
+                "\n"
+                "  %2%\n"
+                "\n"
+                "To remove the existing package:\n"
+                "\n"
+                "  nix profile remove %3%\n"
+                "\n"
+                "The new package can also be installed next to the existing one by assigning a different priority.\n"
+                "The conflicting packages have a priority of %5%.\n"
+                "To prioritise the new package:\n"
+                "\n"
+                "  nix profile install %4% --priority %6%\n"
+                "\n"
+                "To prioritise the existing package:\n"
+                "\n"
+                "  nix profile install %4% --priority %7%\n",
+                originalConflictingFilePath,
+                newConflictingFilePath,
+                originalConflictingRef.to_string(),
+                newConflictingRef.to_string(),
+                conflictError.priority,
+                conflictError.priority - 1,
+                conflictError.priority + 1
+            );
+        }
     }
 };