refactor(pgrx): conditionally apply rustc wrapper when < 0.12

Replace inline bash script generation with writeShellScriptBin for rustc
wrapper that filters empty postmaster_stub.rs arguments. Apply wrapper only
for pgrx < 0.12 since issue was fixed upstream in pgrx#1435 and pgrx#1441.

Author: yvan-sraka

nix/cargo-pgrx/buildPgrxExtension.nix

@@ -28,7 +28,6 @@
 # SOFTWARE.
 {
   lib,
-  bash,
   cargo-pgrx,
   pkg-config,
   rustPlatform,
@@ -86,6 +85,27 @@ let
   fakeRustfmt = writeShellScriptBin "rustfmt" ''
     exit 0
   '';
+
+  # Rustc wrapper for pgrx < 0.12.0 to filter out empty postmaster_stub.rs arguments
+  # This fixes an issue that causes build failures.
+  # Fixed upstream in pgcentralfoundation/pgrx#1435 and #1441, available from pgrx >= 0.12.
+  rustcWrapper = writeShellScriptBin "rustc" ''
+    # ORIGINAL_RUSTC is set in the buildPhase before this wrapper is added to PATH
+    original_rustc="''${ORIGINAL_RUSTC:-rustc}"
+    filtered_args=()
+    for arg in "$@"; do
+      if [[ -z "$arg" ]]; then
+        continue
+      fi
+      if [[ "$arg" =~ postmaster_stub\.rs$ ]]; then
+        if [[ ! -s "$arg" ]]; then
+          continue
+        fi
+      fi
+      filtered_args+=("$arg")
+    done
+    exec "$original_rustc" "''${filtered_args[@]}"
+  '';
   maybeDebugFlag = lib.optionalString (buildType != "release") "--debug";
   maybeEnterBuildAndTestSubdir = lib.optionalString (buildAndTestSubdir != null) ''
     export CARGO_TARGET_DIR="$(pwd)/target"
@@ -94,6 +114,10 @@ let
   maybeLeaveBuildAndTestSubdir = lib.optionalString (buildAndTestSubdir != null) "popd";
   pgrxBinaryName = if builtins.compareVersions "0.7.4" cargo-pgrx.version >= 0 then "pgx" else "pgrx";
 
+  # The rustc wrapper is only needed for pgrx < 0.12.0
+  # fixed upstream in pgcentralfoundation/pgrx#1435 and #1441
+  needsRustcWrapper = builtins.compareVersions cargo-pgrx.version "0.12.0" < 0;
+
   pgrxPostgresMajor = lib.versions.major postgresql.version;
   preBuildAndTest = ''
     export PGRX_HOME=$(mktemp -d)
@@ -137,48 +161,31 @@ let
       ++ lib.optionals useFakeRustfmt [ fakeRustfmt ];
 
     buildPhase = ''
-            runHook preBuild
-
-            echo "Executing cargo-pgrx buildPhase"
-            ${preBuildAndTest}
-            ${maybeEnterBuildAndTestSubdir}
-
-            export PGRX_BUILD_FLAGS="--frozen -j $NIX_BUILD_CORES ${builtins.concatStringsSep " " cargoBuildFlags}"
-            export PGX_BUILD_FLAGS="$PGRX_BUILD_FLAGS"
-
-            # Wrap rustc to filter out empty postmaster_stub.rs arguments
-            original_rustc=$(command -v rustc)
-            mkdir -p $out/bin
-            cat > $out/bin/rustc << EOF
-      #!${bash}/bin/bash
-      filtered_args=()
-      for arg in "\$@"; do
-        if [[ -z "\$arg" ]]; then
-          continue
-        fi
-        if [[ "\$arg" =~ postmaster_stub\.rs$ ]]; then
-          if [[ ! -s "\$arg" ]]; then
-            continue
-          fi
-        fi
-        filtered_args+=("\$arg")
-      done
-      exec "$original_rustc" "\''${filtered_args[@]}"
-      EOF
-            chmod +x $out/bin/rustc
-            export PATH="$out/bin:$PATH"
-            export RUSTC="$out/bin/rustc"
-
-            ${lib.optionalString stdenv.hostPlatform.isDarwin ''RUSTFLAGS="''${RUSTFLAGS:+''${RUSTFLAGS} }-Clink-args=-Wl,-undefined,dynamic_lookup"''} \
-            cargo ${pgrxBinaryName} package \
-              --pg-config ${lib.getDev postgresql}/bin/pg_config \
-              ${maybeDebugFlag} \
-              --features "${builtins.concatStringsSep " " buildFeatures}" \
-              --out-dir "$out"
-
-            ${maybeLeaveBuildAndTestSubdir}
-
-            runHook postBuild
+      runHook preBuild
+
+      echo "Executing cargo-pgrx buildPhase"
+      ${preBuildAndTest}
+      ${maybeEnterBuildAndTestSubdir}
+
+      export PGRX_BUILD_FLAGS="--frozen -j $NIX_BUILD_CORES ${builtins.concatStringsSep " " cargoBuildFlags}"
+      export PGX_BUILD_FLAGS="$PGRX_BUILD_FLAGS"
+
+      ${lib.optionalString needsRustcWrapper ''
+        export ORIGINAL_RUSTC="$(command -v ${stdenv.cc.targetPrefix}rustc || command -v rustc)"
+        export PATH="${rustcWrapper}/bin:$PATH"
+        export RUSTC="${rustcWrapper}/bin/rustc"
+      ''}
+
+      ${lib.optionalString stdenv.hostPlatform.isDarwin ''RUSTFLAGS="''${RUSTFLAGS:+''${RUSTFLAGS} }-Clink-args=-Wl,-undefined,dynamic_lookup"''} \
+      cargo ${pgrxBinaryName} package \
+        --pg-config ${lib.getDev postgresql}/bin/pg_config \
+        ${maybeDebugFlag} \
+        --features "${builtins.concatStringsSep " " buildFeatures}" \
+        --out-dir "$out"
+
+      ${maybeLeaveBuildAndTestSubdir}
+
+      runHook postBuild
     '';
 
     preCheck = preBuildAndTest + args.preCheck or "";