cobalt_lint

Lint rules for Cobalt that report a broken annotation or a missing registration in the editor, instead of only when build_runner runs.

Turn it on in analysis_options.yaml at the root of your package or workspace:

plugins:
  cobalt_lint: ^1.0.0

The IDE and dart analyze then flag a mistake where you make it:

@cobaltInject
class CartController extends ChangeNotifier {}
// warning: 'CartController' is registered and declares 'dispose()', but nothing
//          tells the scope to call it. (cobalt_registration_is_never_released)

Its quick fix adds implements Disposable, and the scope closes the controller with everything else.

Learn more: every rule, the quick fixes, and the lint plugin in the Code-Gen guide.

Where the plugin comes from

The plugins section only works at the root of a package or workspace — a nested analysis_options.yaml is silently ignored, and dart analyze <nested/dir> will not apply it.

The plugin is resolved from pub.flutter-io.cn, not from your pubspec. The analysis server builds its own plugin_entrypoint package and runs pub upgrade on it, so a dependency_override in your pubspec.yaml has no effect on which cobalt_lint gets loaded. To point the server at local sources — the only option against unpublished packages — name them inside the plugins section itself:

plugins:
  cobalt_lint:
    path: ../packages/cobalt_lint
  dependency_overrides:
    cobalt_lint:
      path: ../packages/cobalt_lint
    cobalt_analyzer:
      path: ../packages/cobalt_analyzer

The second thing outside your pubspec

The synthetic plugin_entrypoint also depends on analysis_server_plugin at a version the SDK chooses, not one you write. An SDK that vendors an unpublished version asks pub.flutter-io.cn for something like ^0.3.21-dev, finds nothing, and analysis fails before a single file is read:

Because plugin_entrypoint depends on analysis_server_plugin ^0.3.21-dev
which doesn't match any versions, version solving failed.

That case — an SDK vendoring a version pub.flutter-io.cn has never heard of — usually resolves itself once that version is published. A related one waits for us: analysis_server_plugin pins the analyzer it depends on exactly, and cobalt_lint declares analyzer: ">=10.0.1 <15.0.0", from the Flutter 3.38.9 floor to analyzer 14. An SDK whose bundled analysis_server_plugin needs analyzer 15 makes the same crash until a cobalt_lint release admits that major — the source is kept free of anything that exists on only one side of an analyzer release, so admitting one is a constraint and a test run, not a rewrite.

Neither is a failure of the code being analysed, and neither is fixable from the plugin's side — which is why this repository's own analysis_options.yaml does not enable the plugin, even now that cobalt_lint is published. The block lives in analysis_options.plugin.yaml, copied over by hand, and that split is permanent. The rules themselves are covered by this package's tests, which drive them through analyzer_testing and never start a server.

The overrides above are gone from this repository's own copy now that cobalt_lint is published — analysis_options.plugin.yaml carries the plain three-line form. What does not go away is the plugins: line living in that separate file rather than in analysis_options.yaml itself.

Rules

Rule	Catches
cobalt_missing_injection_mixin	@injected fields without with _$ClassName, on a class the container registers or applies as a decorator
cobalt_injected_field_needs_an_injectable	@injected fields on a class the container neither registers nor applies as a decorator
cobalt_param_needs_an_injectable	@CobaltParam on a class the container never registers
cobalt_injected_field_must_be_late_final	@injected on a mutable, non-late or static field
cobalt_injectable_must_be_constructible	@CobaltInject on an abstract class or one with no public generative constructor
cobalt_init_requires_init_method	@CobaltInit on a class with no init()
cobalt_bootstrap_requires_run_method	@CobaltBootstrap on a class with no run()
cobalt_bootstrap_step_cannot_inject	a bootstrap step whose constructor takes required parameters
cobalt_environment_needs_a_registration	@CobaltEnvironment on a class nothing registers, where it silently does nothing
cobalt_dependency_is_not_registered	an injected dependency nothing in the package registers, or a decorator's target or dependency nothing registers
cobalt_dependency_cycle	an injectable class that depends, eventually, on itself — including through a decorator of it
cobalt_registration_is_never_released	a registered class with a dispose() or close() the scope cannot see
cobalt_resource_is_never_closed	A registration holds something closeable and offers no way to close it.
cobalt_lazy_registration_injected_synchronously	a lazy async registration injected where nothing can wait for it — a synchronous or eager constructor, an @injected field, or a decorator
cobalt_async_transient_read_synchronously	get, getOrNull, getAll or context.cobalt on an async transient, which always throws — resolve it with getAsync
cobalt_depends_on_lazy_registration	@CobaltInit(dependsOn: [...]) naming a lazy async registration, which init() never builds
cobalt_override_needs_type_argument	a CobaltOverride or CobaltParamOverride with no type argument, so Dart infers the key it replaces
cobalt_hook_added_too_late	hookAll after an eager registration or a get on the same scope — in one cascade or earlier in the block — which the scope refuses with CobaltHookError; add hooks before anything is built

All rules are warnings, so they are on by default. Every rule reads annotations through cobalt_analyzer, the same layer the generator uses.

Quick fixes

Seven rules come with a quick fix, offered by the IDE on the diagnostic:

Rule	Fix
cobalt_injected_field_must_be_late_final	declares the field late final
cobalt_missing_injection_mixin	adds _$ClassName to the with clause, or writes one
cobalt_injected_field_needs_an_injectable	adds @cobaltInject above the class
cobalt_environment_needs_a_registration	adds @cobaltInject above the class
cobalt_param_needs_an_injectable	adds @cobaltInject above the class
cobalt_depends_on_lazy_registration	replaces dependsOn: [...] with lazy: true
cobalt_registration_is_never_released	implements Disposable, or AsyncDisposable when the teardown returns a Future, adds a dispose() calling the teardown when it has another name, and imports package:cobalt/cobalt.dart if needed

A fix stays out of the menu where it cannot be sure of the result: @cobaltInject is not offered on an abstract class or where the annotations are imported with a prefix, and Disposable is not offered when the class already has a dispose that is not its teardown.

Why the graph rules report less than the build does

cobalt_registration_is_never_released is the one that pays for itself in a Flutter application. A scope releases what implements Disposable or AsyncDisposable, and Dart has no structural typing — so ChangeNotifier.dispose, which matches the interface method exactly, is invisible to it, and Bloc.close is not even the right name. The rule reports a registered class that declares a teardown-shaped method (no required parameters, returning void or a Future) and neither implements an interface nor names a dispose: function.

It stays quiet where the scope would never call one anyway: a transient and a parameterized registration are not retained. It also stays quiet when a Disposable from somewhere else is in the supertypes, because it matches by name rather than by library — a rule that cannot see the whole graph should fail towards silence.

Thirteen of the eighteen rules answer a question about one declaration or one expression. The other five — cobalt_dependency_is_not_registered, cobalt_dependency_cycle, cobalt_lazy_registration_injected_synchronously, cobalt_depends_on_lazy_registration and cobalt_async_transient_read_synchronously — answer one about the whole package, and the analysis server does not offer that view: it hands a rule one library at a time, and the only synchronous window onto the others is their parsed, unresolved source.

So they share an index of what the package registers, read from syntax — @CobaltInject and @CobaltInit classes, their exposeAs targets, @CobaltModule members (indexed by return type, with one Future layer removed) and @CobaltScopeRoot(provides: [...]) entries — together with what each registration asks for. A decorator is not a registration, so it adds no name; what its constructor asks for, beyond the instance it wraps, joins its target's edges — the decorator runs whenever the target is handed out, so a decorator needing something that depends on its own target is a loop. It holds bare names: no library, no type arguments, no @Named qualifier. Each of those omissions makes the index match more, so the rule stays quiet where the build still objects:

Case	Build	Rule
nothing registers HttpClient	error	reported
@Named('audit') Logger where only an unnamed Logger is registered	error	silent
Repository<Order> where only Repository<User> is registered	error	silent
two same-named classes from different libraries, one registered	error	silent

That asymmetry is deliberate. A false report from an editor that cannot see the whole graph costs more than a missed one, because the build is still there and is still exact. Treat the rules as the fast path, never as the authority.

For a cycle the same coarseness cuts the other way, and needs the opposite care: a shared name makes the graph denser, and a dense graph can grow a loop no real one has. So a name two declarations in the package both claim is dropped from the graph rather than fused, and every registration on the loop is reported — each is a place the loop could be broken. Only one loop is reported at a time, which is what the build does with the same graph.

cobalt_lazy_registration_injected_synchronously reads laziness from the same index: a class marked @cobaltLazyInit or @CobaltInit(lazy: true), and a module member marked @CobaltInject(lazyInit: true) — only as the literal true, the one spelling syntax can read without guessing. A name two declarations claim is left out, so the rule cannot report a class for injecting something that may not be lazy at all.

The index is rebuilt when a file in lib changes, and checked by modification stamp otherwise — listing costs a stat per file, building costs a parse per file. If any file will not parse, the rule reports nothing at all rather than mistake a skipped file for a missing registration.

Manual Mode is out of reach for the same reason it is out of reach for the generator: a hand-written factory resolves inside create, and nothing static can see what it will ask for.

Why @injected has two rules

They look like one question and are two, with different answers. On a class the container registers, the mixin exists and the fix is to mix it in — cobalt_missing_injection_mixin. On a class it does not, no mixin is written for it at all, so with _$ClassName sends you to a name that will never be generated; the fix is to annotate the class or drop @injected, which is cobalt_injected_field_needs_an_injectable.

Both use the same reading of "registers" the generator does — @CobaltInject and @CobaltInit alike. cobalt_param_needs_an_injectable is the same shape for @CobaltParam: on a class the container does not know, the marking is read by nobody and the class is constructed by hand exactly as before.