Bad conditional imports are not properly reported by build_modules.

[schultek]

The build_modules package should nicely report bad or broken imports that cause a compilation failure. This works fine for normal imports, but does not for conditional imports where the conditionally imported part is broken.

Repro:

1. dart create -t web myapp
2. Create an empty lib/something.dart file.
3. Add import 'package:myapp/something.dart' if (dart.library.js_interop) 'package:something/broken.dart'; to web/main.dart.
4. Run dart run build_runner build

Expected:

Build fails and prints error:

Unable to find modules for some sources, this is usually the result of either a                                                              
  bad import, a missing dependency in a package (or possibly a dev_dependency                                                                  
  needs to move to a real dependency), or a build failure (if importing a                                                                      
  generated file).                                                                                                                             
                                                                                                                                               
  Please check the following imports:    
  
  `import 'package:myapp/something.dart' if (dart.library.js_interop) 'package:myapp/broken.dart';` from myapp|web/main.dart at 3:1

Actual:

Build fails and prints error:

Unable to find modules for some sources, this is usually the result of either a                                                              
  bad import, a missing dependency in a package (or possibly a dev_dependency                                                                  
  needs to move to a real dependency), or a build failure (if importing a                                                                      
  generated file).                                                                                                                             
                                                                                                                                               
  Please check the following imports:    
  

There is no actual import reported after "Please check the following imports: ", which makes it super unhelpful and almost impossible to actually find the problem in a real-world project, especially because someone (me) coming across this doesn't know to look for broken conditional imports and potentially (literally) wastes hours looking for the cause of this.

---

• Dart SDK version: 3.10.0 (stable) (Thu Nov 6 05:24:55 2025 -0800) on "macos_arm64"
• build_modules: 5.1.4