Remove a provably-dead if (x == null) guard
io.moderne.nullability.RemoveProvablyDeadNullGuardio.moderne.recipe:rewrite-nullabilityRemoves an if (x == null) { ... } guard whose then-branch the flow engine proves unreachable because x is already non-null at that point (e.g. after an earlier assertion, guard, or assignment). Such a guard is dead code: the x == null test can never be true, so its then-branch never executes and deleting it — while keeping any else body, the only live path — preserves behavior. To match the aggressiveness Airbnb endorses and no further, the removal fires only when the path-sensitive flow analysis decisively proves x non-null at the guard, and never on a parameter of a public method (the service-edge / untrusted-input validation point NullAway guidance explicitly excludes). The condition must be a bare x == null / null == x on a simple local or parameter; a compound condition, a field, or anything not flow-proven is left untouched. Behavior-preserving (it removes only unreachable code), idempotent, and conservative; only Java sources are modified.
Usage
This recipe has no required configuration options. You’ll need the Moderne CLI configured before running the command below.
mod run . --recipe io.moderne.nullability.RemoveProvablyDeadNullGuardIf the recipe isn’t available locally, install it with:
mod config recipes jar install io.moderne.recipe:rewrite-nullability:0.3.1Options
| Name | Type | Description |
|---|---|---|
annotatedPackages | String | Comma-separated package prefixes to limit the fix to (matching NullAway's AnnotatedPackages option). When unset, the recipe fixes all packages.e.g. com.example |
Data tables
Structured output this recipe can produce.
- Null-safety fixes by rungEach residual null-safety fix applied, tagged with the precedence rung that produced it, so the share bottoming out at a last-resort `requireNonNull` assertion can be tracked.
io.moderne.nullability.table.NullFixes - Declined null-safety fixes needing reviewEach site the recipe declined to auto-fix because the fix is a design decision (the value is explicitly `null` on some path, so the slot likely should be `@Nullable`), for human triage.
io.moderne.nullability.table.DeclinedNullFixes - Source files that had resultsSource files that were modified by the recipe run.
org.openrewrite.table.SourcesFileResults - Source files that had search resultsSearch results that were found during the recipe run.
org.openrewrite.table.SearchResults - Source files that errored on a recipeThe details of all errors produced by a recipe run.
org.openrewrite.table.SourcesFileErrors - Recipe performanceStatistics used in analyzing the performance of recipes.
org.openrewrite.table.RecipeRunStats