Merge pull request #7283 from hercules-ci/issue-6572

Fix #6572 `requires non-existent output`

src/libstore/build/derivation-goal.cc

@@ -528,14 +528,32 @@ void DerivationGoal::inputsRealised()
             /* Add the relevant output closures of the input derivation
                `i' as input paths.  Only add the closures of output paths
                that are specified as inputs. */
-            for (auto & j : wantedDepOutputs)
-                if (auto outPath = get(inputDrvOutputs, { depDrvPath, j }))
+            for (auto & j : wantedDepOutputs) {
+                /* TODO (impure derivations-induced tech debt):
+                   Tracking input derivation outputs statefully through the
+                   goals is error prone and has led to bugs.
+                   For a robust nix, we need to move towards the `else` branch,
+                   which does not rely on goal state to match up with the
+                   reality of the store, which is our real source of truth.
+                   However, the impure derivations feature still relies on this
+                   fragile way of doing things, because its builds do not have
+                   a representation in the store, which is a usability problem
+                   in itself */
+                if (auto outPath = get(inputDrvOutputs, { depDrvPath, j })) {
                     worker.store.computeFSClosure(*outPath, inputPaths);
-                else
+                }
+                else {
+                    auto outMap = worker.evalStore.queryDerivationOutputMap(depDrvPath);
+                    auto outMapPath = outMap.find(j);
+                    if (outMapPath == outMap.end()) {
                         throw Error(
                             "derivation '%s' requires non-existent output '%s' from input derivation '%s'",
                             worker.store.printStorePath(drvPath), j, worker.store.printStorePath(depDrvPath));
                     }
+                    worker.store.computeFSClosure(outMapPath->second, inputPaths);
+                }
+            }
+        }
     }
 
     /* Second, the input sources. */

tests/build.sh

@@ -70,3 +70,54 @@ testNormalization () {
 }
 
 testNormalization
+
+# https://github.com/NixOS/nix/issues/6572
+issue_6572_independent_outputs() {
+    nix build -f multiple-outputs.nix --json independent --no-link > $TEST_ROOT/independent.json
+
+    # Make sure that 'nix build' can build a derivation that depends on both outputs of another derivation.
+    p=$(nix build -f multiple-outputs.nix use-independent --no-link --print-out-paths)
+    nix-store --delete "$p" # Clean up for next test
+
+    # Make sure that 'nix build' tracks input-outputs correctly when a single output is already present.
+    nix-store --delete "$(jq -r <$TEST_ROOT/independent.json .[0].outputs.first)"
+    p=$(nix build -f multiple-outputs.nix use-independent --no-link --print-out-paths)
+    cmp $p <<EOF
+first
+second
+EOF
+    nix-store --delete "$p" # Clean up for next test
+
+    # Make sure that 'nix build' tracks input-outputs correctly when a single output is already present.
+    nix-store --delete "$(jq -r <$TEST_ROOT/independent.json .[0].outputs.second)"
+    p=$(nix build -f multiple-outputs.nix use-independent --no-link --print-out-paths)
+    cmp $p <<EOF
+first
+second
+EOF
+    nix-store --delete "$p" # Clean up for next test
+}
+issue_6572_independent_outputs
+
+
+# https://github.com/NixOS/nix/issues/6572
+issue_6572_dependent_outputs() {
+
+    nix build -f multiple-outputs.nix --json a --no-link > $TEST_ROOT/a.json
+
+    # # Make sure that 'nix build' can build a derivation that depends on both outputs of another derivation.
+    p=$(nix build -f multiple-outputs.nix use-a --no-link --print-out-paths)
+    nix-store --delete "$p" # Clean up for next test
+
+    # Make sure that 'nix build' tracks input-outputs correctly when a single output is already present.
+    nix-store --delete "$(jq -r <$TEST_ROOT/a.json .[0].outputs.second)"
+    p=$(nix build -f multiple-outputs.nix use-a --no-link --print-out-paths)
+    cmp $p <<EOF
+first
+second
+EOF
+    nix-store --delete "$p" # Clean up for next test
+}
+if isDaemonNewer "2.12pre0"; then
+    issue_6572_dependent_outputs
+fi

tests/multiple-outputs.nix

@@ -31,6 +31,15 @@ rec {
     helloString = "Hello, world!";
   };
 
+  use-a = mkDerivation {
+    name = "use-a";
+    inherit (a) first second;
+    builder = builtins.toFile "builder.sh"
+      ''
+        cat $first/file $second/file >$out
+      '';
+  };
+
   b = mkDerivation {
     defaultOutput = assert a.second.helloString == "Hello, world!"; a;
     firstOutput = assert a.outputName == "first"; a.first.first;
@@ -87,4 +96,25 @@ rec {
     buildCommand = "mkdir $a $b $c";
   };
 
+  independent = mkDerivation {
+    name = "multiple-outputs-independent";
+    outputs = [ "first" "second" ];
+    builder = builtins.toFile "builder.sh"
+      ''
+        mkdir $first $second
+        test -z $all
+        echo "first" > $first/file
+        echo "second" > $second/file
+      '';
+  };
+
+  use-independent = mkDerivation {
+    name = "use-independent";
+    inherit (a) first second;
+    builder = builtins.toFile "builder.sh"
+      ''
+        cat $first/file $second/file >$out
+      '';
+  };
+
 }