`dcm check-unused-code` false positives

[kenzieschmoll]

Command: dcm check-unused-code packages/devtools_app/ --exclude-public-api

False positives (one common theme I see here is that anything used in assert statements is falsely determined "unused"):

packages/devtools_app/test/test_infra/utils/extent_delegate_utils.dart (1 issue):
    ✖ unused field _renderObjectInitialized
      at packages/devtools_app/test/test_infra/utils/extent_delegate_utils.dart:19:3

packages/devtools_app/lib/src/extensions/embedded/_controller_web.dart (1 issue):
    ✖ unused field _initialized
      at packages/devtools_app/lib/src/extensions/embedded/_controller_web.dart:81:3

packages/devtools_app/lib/src/framework/home_screen.dart (2 issues):
    ✖ unused method _debugInitVmServiceCache
      at packages/devtools_app/lib/src/framework/home_screen.dart:174:3

packages/devtools_app/lib/src/app.dart (2 issues):
    ✖ unused class _AlternateCheckedModeBanner
      at packages/devtools_app/lib/src/app.dart:616:1
    ✖ unused constructor _AlternateCheckedModeBanner
      at packages/devtools_app/lib/src/app.dart:622:3

packages/devtools_app/lib/src/screens/performance/panes/timeline_events/perfetto/_perfetto_controller_web.dart (1 issue):
    ✖ unused field _initialized
      at packages/devtools_app/lib/src/screens/performance/panes/timeline_events/perfetto/_perfetto_controller_web.dart:162:3

I will add more false positives to this list as I find them (working through different directories #9906).

@incendial

[incendial]

@kenzieschmoll trying to reproduce these and I'm getting ✔ no unused code found!. What DCM version do you have? I'm running with the latest 1.38.3.

Also, adding // ignore: unused-code for code that is no longer used only in asserts is not needed (e.g, _AlternateCheckedModeBanner or _debugInitVmServiceCache).
By default, the tool skips usages in asserts so that assert-only usages at least have a comment with the context of why that code is assert-only. Maybe we should have that in our docs.

[incendial]

Ah, I see, there are excludes that need to be removed first, now I can reproduce it.

[incendial]

Fixed for both _initialized fields and _renderObjectInitialized, will be in the next release.

[kenzieschmoll]

I am now on 1.38.3.

Another false positive (line numbers may be off because I am on my local branch with changes):

packages/devtools_app/lib/src/shared/primitives/utils.dart (2 issues):
    ✖ this getter is used but never assigned a value
      at packages/devtools_app/lib/src/shared/primitives/utils.dart:450:3
    ✖ this getter is used but never assigned a value
      at packages/devtools_app/lib/src/shared/primitives/utils.dart:452:3

Associated code:

extension SafeAccess<T> on Iterable<T> {
  T? get safeFirst => isNotEmpty ? first : null;

  T? get safeLast => isNotEmpty ? last : null;
}

[incendial]

Thanks. I'm very surprised to see a getter falling into the "not assigned" category 😅🙈
But I was able to reproduce it, investigating

Edit: fixed, will be in the next release

[kenzieschmoll]

Another false positive:

packages/devtools_shared/lib/src/utils/file_utils.dart (1 issue):
    ✖ unused top level variable _fileUriPrefix
      at packages/devtools_shared/lib/src/utils/file_utils.dart:8:1