From 12df8885cc70499cc8fa2bfe73992c6d37ec332e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 13 Jul 2022 13:39:06 +0200
Subject: [PATCH] Simplify the check for overrides on non-existent inputs

---
 src/libexpr/flake/flake.cc | 47 ++++++++++----------------------------
 tests/flakes.sh            |  4 +++-
 2 files changed, 15 insertions(+), 36 deletions(-)

diff --git a/src/libexpr/flake/flake.cc b/src/libexpr/flake/flake.cc
index 233e52407..cc9be1336 100644
--- a/src/libexpr/flake/flake.cc
+++ b/src/libexpr/flake/flake.cc
@@ -352,39 +352,6 @@ LockedFlake lockFlake(
 
         std::vector<FlakeRef> parents;
 
-        std::function<void(
-            const InputPath & inputPathPrefix,
-            const FlakeInputs & flakeInputs
-            )>
-            checkFollowsDeclarations;
-
-        checkFollowsDeclarations = [&](
-            const InputPath & inputPathPrefix,
-            const FlakeInputs & flakeInputs
-        ) {
-            for (auto [inputPath, inputOverride] : overrides) {
-                auto inputPath2(inputPath);
-                auto follow = inputPath2.back();
-                inputPath2.pop_back();
-                if (inputPath2 == inputPathPrefix
-                    && flakeInputs.find(follow) == flakeInputs.end()
-                ) {
-                    std::string root;
-                    for (auto & element : inputPath2) {
-                        root.append(element);
-                        if (element != inputPath2.back()) {
-                            root.append(".inputs.");
-                        }
-                    }
-                    warn(
-                        "%s has a `follows'-declaration for a non-existent input %s!",
-                        root,
-                        follow
-                    );
-                }
-            }
-        };
-
         std::function<void(
             const FlakeInputs & flakeInputs,
             std::shared_ptr<Node> node,
@@ -406,8 +373,6 @@ LockedFlake lockFlake(
         {
             debug("computing lock file node '%s'", printInputPath(inputPathPrefix));
 
-            checkFollowsDeclarations(inputPathPrefix, flakeInputs);
-
             /* Get the overrides (i.e. attributes of the form
                'inputs.nixops.inputs.nixpkgs.url = ...'). */
             for (auto & [id, input] : flakeInputs) {
@@ -419,6 +384,18 @@ LockedFlake lockFlake(
                 }
             }
 
+            /* Check whether this input has overrides for a
+               non-existent input. */
+            for (auto [inputPath, inputOverride] : overrides) {
+                auto inputPath2(inputPath);
+                auto follow = inputPath2.back();
+                inputPath2.pop_back();
+                if (inputPath2 == inputPathPrefix && !flakeInputs.count(follow))
+                    warn(
+                        "input '%s' has an override for a non-existent input '%s'",
+                        printInputPath(inputPathPrefix), follow);
+            }
+
             /* Go over the flake inputs, resolve/fetch them if
                necessary (i.e. if they're new or the flakeref changed
                from what's in the lock file). */
diff --git a/tests/flakes.sh b/tests/flakes.sh
index 9087e1978..9838848eb 100644
--- a/tests/flakes.sh
+++ b/tests/flakes.sh
@@ -869,6 +869,7 @@ cat >$flakeFollowsA/flake.nix <<EOF
     inputs.B = {
         url = "path:./flakeB";
         inputs.invalid.follows = "D";
+        inputs.invalid2.url = "path:./flakeD";
     };
     inputs.D.url = "path:./flakeD";
     outputs = { ... }: {};
@@ -877,4 +878,5 @@ EOF
 
 git -C $flakeFollowsA add flake.nix
 
-nix flake lock $flakeFollowsA 2>&1 | grep "warning: B has a \`follows'-declaration for a non-existant input invalid!"
+nix flake lock $flakeFollowsA 2>&1 | grep "warning: input 'B' has an override for a non-existent input 'invalid'"
+nix flake lock $flakeFollowsA 2>&1 | grep "warning: input 'B' has an override for a non-existent input 'invalid2'"