core/pkgs/build-support/flutter/default.nix

{ lib
, callPackage
, runCommand
, makeWrapper
, wrapGAppsHook
, buildDartApplication
, cacert
, glib
, flutter
, pkg-config
, jq
, yq
, moreutils
}:

# absolutely no mac support for now

{ pubGetScript ? "flutter pub get"
, flutterBuildFlags ? [ ]
, targetFlutterPlatform ? "linux"
, extraWrapProgramArgs ? ""
, ...
}@args:

let
  builderArgs = rec {
    universal = args // {
      sdkSetupScript = ''
        # Pub needs SSL certificates. Dart normally looks in a hardcoded path.
        # https://github.com/dart-lang/sdk/blob/3.1.0/runtime/bin/security_context_linux.cc#L48
        #
        # Dart does not respect SSL_CERT_FILE...
        # https://github.com/dart-lang/sdk/issues/48506
        # ...and Flutter does not support --root-certs-file, so the path cannot be manually set.
        # https://github.com/flutter/flutter/issues/56607
        # https://github.com/flutter/flutter/issues/113594
        #
        # libredirect is of no use either, as Flutter does not pass any
        # environment variables (including LD_PRELOAD) to the Pub process.
        #
        # Instead, Flutter is patched to allow the path to the Dart binary used for
        # Pub commands to be overriden.
        export NIX_FLUTTER_PUB_DART="${runCommand "dart-with-certs" { nativeBuildInputs = [ makeWrapper ]; } ''
          mkdir -p "$out/bin"
          makeWrapper ${flutter.dart}/bin/dart "$out/bin/dart" \
            --add-flags "--root-certs-file=${cacert}/etc/ssl/certs/ca-bundle.crt"
        ''}/bin/dart"

        export HOME="$NIX_BUILD_TOP"
        flutter config --no-analytics &>/dev/null # mute first-run
        flutter config --enable-linux-desktop >/dev/null
      '';

      inherit pubGetScript;

      sdkSourceBuilders = {
        # https://github.com/dart-lang/pub/blob/68dc2f547d0a264955c1fa551fa0a0e158046494/lib/src/sdk/flutter.dart#L81
        "flutter" = name: runCommand "flutter-sdk-${name}" { passthru.packageRoot = "."; } ''
          for path in '${flutter}/packages/${name}' '${flutter}/bin/cache/pkg/${name}'; do
            if [ -d "$path" ]; then
              ln -s "$path" "$out"
              break
            fi
          done

          if [ ! -e "$out" ]; then
            echo 1>&2 'The Flutter SDK does not contain the requested package: ${name}!'
            exit 1
          fi
        '';
      };

      extraPackageConfigSetup = ''
        # https://github.com/flutter/flutter/blob/3.13.8/packages/flutter_tools/lib/src/dart/pub.dart#L755
        if [ "$('${yq}/bin/yq' '.flutter.generate // false' pubspec.yaml)" = "true" ]; then
          '${jq}/bin/jq' '.packages |= . + [{
            name: "flutter_gen",
            rootUri: "flutter_gen",
            languageVersion: "2.12",
          }]' "$out" | '${moreutils}/bin/sponge' "$out"
        fi
      '';
    };

    linux = universal // {
      outputs = universal.outputs or [ ] ++ [ "debug" ];

      nativeBuildInputs = (universal.nativeBuildInputs or [ ]) ++ [
        wrapGAppsHook

        # Flutter requires pkg-config for Linux desktop support, and many plugins
        # attempt to use it.
        #
        # It is available to the `flutter` tool through its wrapper, but it must be
        # added here as well so the setup hook adds plugin dependencies to the
        # pkg-config search paths.
        pkg-config
      ];

      buildInputs = (universal.buildInputs or [ ]) ++ [ glib ];

      dontDartBuild = true;
      buildPhase = universal.buildPhase or ''
        runHook preBuild

        mkdir -p build/flutter_assets/fonts

        flutter build linux -v --release --split-debug-info="$debug" ${builtins.concatStringsSep " " (map (flag: "\"${flag}\"") flutterBuildFlags)}

        runHook postBuild
      '';

      dontDartInstall = true;
      installPhase = universal.installPhase or ''
        runHook preInstall

        built=build/linux/*/release/bundle

        mkdir -p $out/bin
        mv $built $out/app

        for f in $(find $out/app -iname "*.desktop" -type f); do
          install -D $f $out/share/applications/$(basename $f)
        done

        for f in $(find $out/app -maxdepth 1 -type f); do
          ln -s $f $out/bin/$(basename $f)
        done

        # make *.so executable
        find $out/app -iname "*.so" -type f -exec chmod +x {} +

        # remove stuff like /build/source/packages/ubuntu_desktop_installer/linux/flutter/ephemeral
        for f in $(find $out/app -executable -type f); do
          if patchelf --print-rpath "$f" | grep /build; then # this ignores static libs (e,g. libapp.so) also
            echo "strip RPath of $f"
            newrp=$(patchelf --print-rpath $f | sed -r "s|/build.*ephemeral:||g" | sed -r "s|/build.*profile:||g")
            patchelf --set-rpath "$newrp" "$f"
          fi
        done

        runHook postInstall
      '';

      dontWrapGApps = true;
      extraWrapProgramArgs = ''
        ''${gappsWrapperArgs[@]} \
        ${extraWrapProgramArgs}
      '';
    };

    web = universal // {
      dontDartBuild = true;
      buildPhase = universal.buildPhase or ''
        runHook preBuild

        mkdir -p build/flutter_assets/fonts

        flutter build web -v --release ${builtins.concatStringsSep " " (map (flag: "\"${flag}\"") flutterBuildFlags)}

        runHook postBuild
      '';

      dontDartInstall = true;
      installPhase = universal.installPhase or ''
        runHook preInstall

        cp -r build/web "$out"

        runHook postInstall
      '';
    };
  }.${targetFlutterPlatform} or (throw "Unsupported Flutter host platform: ${targetFlutterPlatform}");

  minimalFlutter = flutter.override { supportedTargetFlutterPlatforms = [ "universal" targetFlutterPlatform ]; };

  buildAppWith = flutter: buildDartApplication.override { dart = flutter; };
in
buildAppWith minimalFlutter (builderArgs // { passthru = builderArgs.passthru or { } // { multiShell = buildAppWith flutter builderArgs; }; })