Merge pull request #211082 from hercules-ci/fix-issue-16182

Fix issue 16182  `Error: _assignFirst found no valid variant!`

doc/stdenv/stdenv.chapter.md

@@ -253,7 +253,7 @@ The propagated equivalent of `depsTargetTarget`. This is prefixed for the same r
 
 #### `NIX_DEBUG` {#var-stdenv-NIX_DEBUG}
 
-A natural number indicating how much information to log. If set to 1 or higher, `stdenv` will print moderate debugging information during the build. In particular, the `gcc` and `ld` wrapper scripts will print out the complete command line passed to the wrapped tools. If set to 6 or higher, the `stdenv` setup script will be run with `set -x` tracing. If set to 7 or higher, the `gcc` and `ld` wrapper scripts will also be run with `set -x` tracing.
+A number between 0 and 7 indicating how much information to log. If set to 1 or higher, `stdenv` will print moderate debugging information during the build. In particular, the `gcc` and `ld` wrapper scripts will print out the complete command line passed to the wrapped tools. If set to 6 or higher, the `stdenv` setup script will be run with `set -x` tracing. If set to 7 or higher, the `gcc` and `ld` wrapper scripts will also be run with `set -x` tracing.
 
 ### Attributes affecting build properties {#attributes-affecting-build-properties}
 

pkgs/build-support/setup-hooks/multiple-outputs.sh

@@ -4,16 +4,32 @@ preFixupHooks+=(_multioutDocs)
 preFixupHooks+=(_multioutDevs)
 postFixupHooks+=(_multioutPropagateDev)
 
-# Assign the first string containing nonempty variable to the variable named $1
+# _assignFirst varName otherVarNames*
+#
+# Set the value of the variable named $varName to the first of otherVarNames
+# that refers to a non-empty variable name.
+#
+# If none of otherVarNames refers to a non-empty variable, the error message is
+# specific to this function's use case, which is setting up the output variables.
 _assignFirst() {
     local varName="$1"
     local REMOVE=REMOVE # slightly hacky - we allow REMOVE (i.e. not a variable name)
     shift
-    while (( $# )); do
-        if [ -n "${!1-}" ]; then eval "${varName}"="$1"; return; fi
-        shift
+    for var in "$@"; do
+        if [ -n "${!var-}" ]; then eval "${varName}"="${var}"; return; fi
     done
-    echo "Error: _assignFirst found no valid variant!"
+    echo
+    echo "error: _assignFirst: could not find a non-empty variable to assign to ${varName}."
+    echo "       The following variables were all unset or empty:"
+    echo "           $*"
+    if [ -z "${out:-}" ]; then
+        echo '       If you do not want an "out" output in your derivation, make sure to define'
+        echo '       the other specific required outputs. This can be achieved by picking one'
+        echo "       of the above as an output."
+        echo '       You do not have to remove "out" if you want to have a different default'
+        echo '       output, because the first output is taken as a default.'
+        echo
+    fi
     return 1 # none found
 }
 

pkgs/build-support/testers/expect-failure.sh

@@ -35,6 +35,14 @@ echo "testBuildFailure: Original builder produced exit code: $r"
 # -----------------------------------------
 # Write the build log to the default output
 
+getAllOutputNames() {
+    if [ -n "$__structuredAttrs" ]; then
+        echo "${!outputs[*]}"
+    else
+        echo "$outputs"
+    fi
+}
+
 outs=( $(getAllOutputNames) )
 defOut=${outs[0]}
 defOutPath=${!defOut}

pkgs/test/stdenv/default.nix

@@ -4,7 +4,8 @@
 { stdenv
 , pkgs
 , lib
-,
+, runCommand
+, testers
 }:
 
 let
@@ -99,6 +100,25 @@ in
   # tests for hooks in `stdenv.defaultNativeBuildInputs`
   hooks = lib.recurseIntoAttrs (import ./hooks.nix { stdenv = bootStdenv; pkgs = earlyPkgs; });
 
+  outputs-no-out = runCommand "outputs-no-out-assert" {
+    result = testers.testBuildFailure (stdenv.mkDerivation {
+      NIX_DEBUG = 1;
+      name = "outputs-no-out";
+      outputs = ["foo"];
+      buildPhase = ":";
+      installPhase = ''
+        touch $foo
+      '';
+    });
+
+    # Assumption: the first output* variable to be configured is
+    #   _overrideFirst outputDev "dev" "out"
+    expectedMsg = "_assignFirst: could not find a non-empty variable to assign to outputDev. The following variables were all unset or empty: dev out.";
+  } ''
+    grep -F "$expectedMsg" $result/testBuildFailure.log >/dev/null
+    touch $out
+  '';
+
   test-env-attrset = testEnvAttrset { name = "test-env-attrset"; stdenv' = bootStdenv; };
 
   # Test compatibility with derivations using `env` as a regular variable.