Any chance to get access to the target OS or target triple in the build phase?

[FrankenApps]

Hi, awesome work, I really like how easy this was to set up.
I am currently working on a PR to rhttp and I was trying to add different environment variables based on the current target platform like this (they are needed due to intricacies of the cc crate):

import 'package:hooks/hooks.dart';
import 'package:code_assets/code_assets.dart';
import 'package:native_toolchain_rust/native_toolchain_rust.dart';

void main(List<String> args) async {
  await build(args, (input, output) async {
    final targetOs = input.config.code.targetOS;
    final cargoEnvironmentVariables = {
      'RUSTFLAGS': '--cfg reqwest_unstable'
    };

    if (targetOs == OS.iOS) {
      cargoEnvironmentVariables['IPHONEOS_DEPLOYMENT_TARGET'] = '13.0';
      cargoEnvironmentVariables['RUSTFLAGS'] = '--cfg reqwest_unstable -C link-arg=-mios-version-min=13.0'; 
    } else if (targetOs == OS.macOS) {
      cargoEnvironmentVariables['MACOSX_DEPLOYMENT_TARGET'] = '10.15';
      cargoEnvironmentVariables['RUSTFLAGS'] = '--cfg reqwest_unstable -C link-arg=-mmacosx-version-min=10.15';
    }

    await RustBuilder(
      assetName: 'src/rust/frb_generated.dart',
      extraCargoEnvironmentVariables: cargoEnvironmentVariables, 
    ).run(input: input, output: output);
  });
}

Unfortunately when I do this at that point, I keep running into this error (way after the build and after the app was already started):

Running Xcode build...
Xcode build done.              119,8s
Installing and launching...     24,6s

Unhandled exception: Null check operator used on a null value
#0 new CodeConfig._fromJson (package:code_assets/src/code_assets/config.dart:52:67) #1 HookConfigCodeConfig.code (package:code_assets/src/code_assets/config.dart:21:37)
#2 main.<anonymous closure> (file:///Users/me/Development/Dart/flutter/rhttp/rhttp/hook/build.dart:7:35)
#3 build (package:hooks/src/api/build_and_link.dart:191:18)
#4 main (file:///Users/me/Development/Dart/flutter/rhttp/rhttp/hook/build.dart:6:9)
#5 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:311:33)
#6 _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)
Building assets for package:rhttp failed.
build.dart returned with exit code: 255.
To reproduce run: (cd /Users/me/Development/Dart/flutter/rhttp/rhttp/; /Users/me/Development/Tools/SDK/Flutter/flutter/bin/cache/dart-sdk/bin/dart --packages=/Users/me/Development/Dart/flutter/rhttp/rhttp/example/.dart_tool/package_config.json /Users/me/Development/Dart/flutter/rhttp/rhttp/example/.dart_tool/hooks_runner/rhttp/337ce265dc/hook.dill --config=/Users/me/Development/Dart/flutter/rhttp/rhttp/example/.dart_tool/hooks_runner/rhttp/337ce265dc/input.json ) 
stderr: Unhandled exception: Null check operator used on a null value
#0 new CodeConfig._fromJson (package:code_assets/src/code_assets/config.dart:52:67)
#1 HookConfigCodeConfig.code (package:code_assets/src/code_assets/config.dart:21:37)
#2 main.<anonymous closure> (file:///Users/me/Development/Dart/flutter/rhttp/rhttp/hook/build.dart:7:35)
#3 build (package:hooks/src/api/build_and_link.dart:191:18)
#4 main (file:///Users/me/Development/Dart/flutter/rhttp/rhttp/hook/build.dart:6:9)
#5 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:311:33)
#6 _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)
stdout: Building native assets failed. See the logs for more details.

Do you think there maybe is a practical way to expose the information about the targetOS and / or target triple to the user?

[GregoryConrad]

Hey! I think targetOS is supposed to be filled in for all builds, and especially Flutter ones. The fact it’s not filled in might be an upstream bug. Would recommend filing an issue there https://github.com/dart-lang/native

[FrankenApps]

I think targetOS is supposed to be filled in for all builds, and especially Flutter ones.

Apparently not, because the latest version reports this more detailed error:

Unhandled exception:
Bad state: HookConfig.code should only be accessed when building code assets. Check HookConfig.buildCodeAssets (e.g. `input.config.buildCodeAssets`)
before accessing HookConfig.code.
#0      HookConfigCodeConfig.code (package:code_assets/src/code_assets/config.dart:24:7)
#1      main.<anonymous closure>
(file:///Users/me/Development/Dart/packages/flutter_native_assets_repro/native_toolchain_c_sample/hook/build.dart:11:35)
#2      build (package:hooks/src/api/build_and_link.dart:250:18)
#3      main (file:///Users/me/Development/Dart/packages/flutter_native_assets_repro/native_toolchain_c_sample/hook/build.dart:10:9)
#4      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:311:33)
#5      _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)


  Building assets for package:native_add_library failed.
  build.dart returned with exit code: 255.
  To reproduce run:
  (cd /Users/me/Development/Dart/packages/flutter_native_assets_repro/native_toolchain_c_sample/;
  /Users/me/Development/Tools/SDK/Flutter/flutter/bin/cache/dart-sdk/bin/dart
  --packages=/Users/me/Development/Dart/packages/flutter_native_assets_repro/native_adder/.dart_tool/package_config.json
  /Users/me/Development/Dart/packages/flutter_native_assets_repro/native_adder/.dart_tool/hooks_runner/native_add_library/337ce265dc/ho
  ok.dill
  --config=/Users/me/Development/Dart/packages/flutter_native_assets_repro/native_adder/.dart_tool/hooks_runner/native_add_library/337c
  e265dc/input.json )
  stderr:
  Unhandled exception:
Bad state: HookConfig.code should only be accessed when building code assets. Check HookConfig.buildCodeAssets (e.g. `input.config.buildCodeAssets`)
before accessing HookConfig.code.
#0      HookConfigCodeConfig.code (package:code_assets/src/code_assets/config.dart:24:7)
#1      main.<anonymous closure>
(file:///Users/me/Development/Dart/packages/flutter_native_assets_repro/native_toolchain_c_sample/hook/build.dart:11:35)
#2      build (package:hooks/src/api/build_and_link.dart:250:18)
#3      main (file:///Users/me/Development/Dart/packages/flutter_native_assets_repro/native_toolchain_c_sample/hook/build.dart:10:9)
#4      _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:311:33)
#5      _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)

  stdout:



Building native assets failed. See the logs for more details.

For this reason I adjusted my build hook like this and now it seems to work just fine:

import 'package:hooks/hooks.dart';
import 'package:code_assets/code_assets.dart';
import 'package:native_toolchain_rust/native_toolchain_rust.dart';

void main(List<String> args) async {
  await build(args, (input, output) async {
    final buildCodeAssets = input.config.buildCodeAssets;
    if (!buildCodeAssets) {
      return;
    }

    final targetOs = input.config.code.targetOS;
    final cargoEnvironmentVariables = {
      'RUSTFLAGS': '--cfg reqwest_unstable'
    };

    if (targetOs == OS.iOS) {
      cargoEnvironmentVariables['IPHONEOS_DEPLOYMENT_TARGET'] = '13.0';
      cargoEnvironmentVariables['RUSTFLAGS'] = '--cfg reqwest_unstable -C link-arg=-mios-version-min=13.0'; 
    } else if (targetOs == OS.macOS) {
      cargoEnvironmentVariables['MACOSX_DEPLOYMENT_TARGET'] = '10.15';
      cargoEnvironmentVariables['RUSTFLAGS'] = '--cfg reqwest_unstable -C link-arg=-mmacosx-version-min=10.15';
    }

    await RustBuilder(
      assetName: 'src/rust/frb_generated.dart',
      extraCargoEnvironmentVariables: cargoEnvironmentVariables, 
    ).run(input: input, output: output);
  });
}