buildGoModule: form GOFLAGS from goFlags

doc/languages-frameworks/go.section.md

@@ -117,6 +117,10 @@ The root directory of the Go module that contains the `go.mod` file.
 
 Defaults to `./`, which is the root of `src`.
 
+### `goFlags` {#var-go-goFlags}
+
+A string list of flags to form the environment variable `GOFLAGS` at the beginning of `buildPhase` and `checkPhase`, overridable via `overrideAttrs`.
+
 ### `ldflags` {#var-go-ldflags}
 
 A string list of flags to pass to the Go linker tool via the `-ldflags` argument of `go build`. Possible values can be retrieved by running `go tool link --help`.

nixos/doc/manual/release-notes/rl-2505.section.md

@@ -40,6 +40,8 @@
 - `binwalk` was updated to 3.1.0, which has been rewritten in rust. The python module is no longer available.
   See the release notes of [3.1.0](https://github.com/ReFirmLabs/binwalk/releases/tag/v3.1.0) for more information.
 
+- `buildGoModule` receives a new argument `goFlags` to form the environment variable `GOFLAGS` during build. `GOFLAGS` specified as a `buildGoModule` argument is assimilated into `goFlags` during evaluation for compatibility purposes, but such way of specification is deprecated and the compatibility behaviour would be removed in future releases.
+
 - `buildGoPackage` has been removed. Use `buildGoModule` instead. See the [Go section in the nixpkgs manual](https://nixos.org/manual/nixpkgs/unstable/#sec-language-go) for details.
 
 - `timescaledb` requires manual upgrade steps.

pkgs/build-support/go/module.nix

@@ -167,12 +167,24 @@ in
 
     inherit (go) GOOS GOARCH;
 
-    GOFLAGS = GOFLAGS
-      ++ lib.warnIf (lib.any (lib.hasPrefix "-mod=") GOFLAGS) "use `proxyVendor` to control Go module/vendor behavior instead of setting `-mod=` in GOFLAGS"
+    inherit CGO_ENABLED enableParallelBuilding GO111MODULE GOTOOLCHAIN;
+
+    goFlags =
+      let
+        # Compatibility layers for direct specification of the GOFLAGS environment variable
+        goFlags =
+          lib.optionals (args?GOFLAGS) (
+            if lib.isString args.GOFLAGS then
+              lib.splitString args.GOFLAGS
+            else args.GOFLAGS
+          ) ++ args.goFlags or [ ];
+      in
+      goFlags
+      ++ lib.warnIf (lib.any (lib.hasPrefix "-mod=") goFlags) "use `proxyVendor` to control Go module/vendor behavior instead of setting `-mod=` in goFlags"
         (lib.optional (!finalAttrs.proxyVendor) "-mod=vendor")
-      ++ lib.warnIf (builtins.elem "-trimpath" GOFLAGS) "`-trimpath` is added by default to GOFLAGS by buildGoModule when allowGoReference isn't set to true"
+      ++ lib.warnIf (builtins.elem "-trimpath" goFlags) "`-trimpath` is added by default to GOFLAGS by buildGoModule when allowGoReference isn't set to true"
         (lib.optional (!allowGoReference) "-trimpath");
-    inherit CGO_ENABLED enableParallelBuilding GO111MODULE GOTOOLCHAIN;
+
 
     # If not set to an explicit value, set the buildid empty for reproducibility.
     ldflags = ldflags ++ lib.optional (!lib.any (lib.hasPrefix "-buildid=") ldflags) "-buildid=";
@@ -197,7 +209,7 @@ in
       # currently pie is only enabled by default in pkgsMusl
       # this will respect the `hardening{Disable,Enable}` flags if set
       if [[ $NIX_HARDENING_ENABLE =~ "pie" ]]; then
-        export GOFLAGS="-buildmode=pie $GOFLAGS"
+        prependToVar goFlags -buildmode=pie
       fi
 
       runHook postConfigure
@@ -209,6 +221,8 @@ in
     ''
       runHook preBuild
 
+      export GOFLAGS="''${goFlags[*]}"
+
       exclude='\(/_\|examples\|Godeps\|testdata'
       if [[ -n "$excludedPackages" ]]; then
         IFS=' ' read -r -a excludedArr <<<$excludedPackages
@@ -283,7 +297,8 @@ in
     checkPhase = args.checkPhase or ''
       runHook preCheck
       # We do not set trimpath for tests, in case they reference test assets
-      export GOFLAGS=''${GOFLAGS//-trimpath/}
+      removeAllPrefixedFromVar goFlags -trimpath
+      export GOFLAGS="''${goFlags[*]}"
 
       for pkg in $(getGoDirs test); do
         buildGoDir test "$pkg"

pkgs/stdenv/generic/setup.sh

@@ -385,6 +385,25 @@ appendToVar() {
     fi
 }
 
+removeAllPrefixedFromVar() {
+    local varName="$1"
+    local -n nameref="$varName"
+    shift
+    if ! [[ -z "${nameref[*]-}" ]] || (("$#" == 0)); then
+        return
+    fi
+    if [[ "$(declare -p "$varName")" =~ "declare -a" ]]; then
+        for prefix in "$@"; do
+            nameref=("${nameref[@]/$prefix}")
+        done
+    else
+        local _arr=()
+        read -ra _arr <<<"$nameref"
+        removeAllPrefixedFromVar _arr "$@"
+        nameref="${_arr[*]}"
+    fi
+}
+
 # Accumulate flags from the named variables $2+ into the indexed array $1.
 #
 # Arrays are simply concatenated, strings are split on whitespace.