flutter.buildFlutterApplication: Allow building for the Web

doc/languages-frameworks/dart.section.md

@@ -103,6 +103,9 @@ flutter.buildFlutterApplication {
   pname = "firmware-updater";
   version = "unstable-2023-04-30";
 
+  # To build for the Web, use the flutterHostPlatform argument.
+  # flutterHostPlatform = "web";
+
   src = fetchFromGitHub {
     owner = "canonical";
     repo = "firmware-updater";

pkgs/build-support/flutter/default.nix

@@ -17,13 +17,14 @@
 
 { pubGetScript ? "flutter pub get"
 , flutterBuildFlags ? [ ]
+, flutterHostPlatform ? "linux"
 , extraWrapProgramArgs ? ""
 , ...
 }@args:
 
-(buildDartApplication.override {
-  dart = flutter;
-}) (args // {
+let
+  hostPlatforms = 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
@@ -79,8 +80,12 @@
           }]' "$out" | '${moreutils}/bin/sponge' "$out"
         fi
       '';
+    };
 
-  nativeBuildInputs = (args.nativeBuildInputs or [ ]) ++ [
+    linux = universal // {
+      outputs = universal.outputs or [ ] ++ [ "debug" ];
+
+      nativeBuildInputs = (universal.nativeBuildInputs or [ ]) ++ [
         wrapGAppsHook
 
         # Flutter requires pkg-config for Linux desktop support, and many plugins
@@ -92,10 +97,10 @@
         pkg-config
       ];
 
-  buildInputs = (args.buildInputs or [ ]) ++ [ glib ];
+      buildInputs = (universal.buildInputs or [ ]) ++ [ glib ];
 
       dontDartBuild = true;
-  buildPhase = args.buildPhase or ''
+      buildPhase = universal.buildPhase or ''
         runHook preBuild
 
         mkdir -p build/flutter_assets/fonts
@@ -106,7 +111,7 @@
       '';
 
       dontDartInstall = true;
-  installPhase = args.installPhase or ''
+      installPhase = universal.installPhase or ''
         runHook preInstall
 
         built=build/linux/*/release/bundle
@@ -134,11 +139,6 @@
           fi
         done
 
-    # Install the package_config.json file.
-    # This is normally done by dartInstallHook, but we disable it.
-    mkdir -p "$pubcache"
-    cp .dart_tool/package_config.json "$pubcache/package_config.json"
-
         runHook postInstall
       '';
 
@@ -147,4 +147,30 @@
         ''${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 "$out"
+
+        runHook postInstall
+      '';
+    };
+  };
+in
+(buildDartApplication.override { dart = flutter.override { supportedTargetFlutterPlatforms = [ "universal" flutterHostPlatform ]; }; })
+  hostPlatforms.${flutterHostPlatform} or "Unsupported Flutter host platform: ${flutterHostPlatform}"

pkgs/development/compilers/flutter/default.nix

@@ -51,12 +51,7 @@ let
     (mkCustomFlutter args).overrideAttrs (prev: next: {
       passthru = next.passthru // rec {
         inherit wrapFlutter mkCustomFlutter mkFlutter;
-        buildFlutterApplication = callPackage ../../../build-support/flutter {
-          # Package a minimal version of Flutter that only uses Linux desktop release artifacts.
-          flutter = (wrapFlutter (mkCustomFlutter args)).override {
-            supportedTargetFlutterPlatforms = [ "universal" "linux" ];
-          };
-        };
+        buildFlutterApplication = callPackage ../../../build-support/flutter { flutter = wrapFlutter (mkCustomFlutter args); };
       };
     });