Add a directive for ignoring imports

Author: mrkkrp

generation_tests/ignore_import/BUILD.in

@@ -0,0 +1,8 @@
+# gazelle:rust_ignore_import false_positive
+
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "lib",
+    srcs = ["lib.rs"],
+)

generation_tests/ignore_import/BUILD.out

@@ -0,0 +1,8 @@
+# gazelle:rust_ignore_import false_positive
+
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "lib",
+    srcs = ["lib.rs"],
+)

generation_tests/ignore_import/README.md

@@ -0,0 +1,5 @@
+The `rust_ignore_import` directive allows ignoring specific imports when resolving dependencies, helping to deal with false positives in the dependency detection logic.
+
+This test verifies:
+1. The directive successfully ignores the specified import (`false_positive`) in the BUILD file where it's defined
+2. The directive does NOT propagate to subdirectories - `subpkg/` will report an error for `false_positive` since it doesn't have its own directive

generation_tests/ignore_import/WORKSPACE

@@ -0,0 +1,2 @@
+gazelle: //subpkg: no match for false_positive
+gazelle: //:lib: no match for real_dep

generation_tests/ignore_import/expectedStderr.txt

@@ -0,0 +1,7 @@
+use real_dep::Something;
+use false_positive::FalsePositive;
+
+fn main() {
+    Something::new();
+    FalsePositive::new();
+}

generation_tests/ignore_import/lib.rs

@@ -0,0 +1,6 @@
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "subpkg",
+    srcs = ["lib.rs"],
+)

generation_tests/ignore_import/subpkg/BUILD.in

@@ -0,0 +1,6 @@
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+rust_library(
+    name = "subpkg",
+    srcs = ["lib.rs"],
+)

generation_tests/ignore_import/subpkg/BUILD.out

@@ -0,0 +1,5 @@
+use false_positive::FalsePositive;
+
+fn helper() {
+    FalsePositive::new();
+}

generation_tests/ignore_import/subpkg/lib.rs

@@ -61,6 +61,10 @@ var (
 	// and rust_proc_macro targets. rust_binary and cargo_build_script targets
 	// continue to list files explicitly.
 	srcsGlobDirective string = "rust_srcs_glob"
+
+	// Ignore a specific import when resolving dependencies.
+	// usage: # gazelle:rust_ignore_import <import name>
+	ignoreImportDirective string = "rust_ignore_import"
 )
 
 type rustConfig struct {
@@ -73,6 +77,7 @@ type rustConfig struct {
 	DefaultFeatures    bool
 	DefaultEdition     string
 	SrcsGlob           bool
+	IgnoredImports     map[string]bool
 }
 
 func (cfg *rustConfig) Clone() *rustConfig {
@@ -88,6 +93,8 @@ func (cfg *rustConfig) Clone() *rustConfig {
 	for k, v := range cfg.KindMapInverse {
 		copy.KindMapInverse[k] = v
 	}
+	// Don't copy IgnoredImports - make rust_ignore_import local to each BUILD file
+	copy.IgnoredImports = make(map[string]bool)
 	return &copy
 }
 
@@ -194,7 +201,7 @@ func (*rustLang) KnownDirectives() []string {
 	return []string{modeDirective, lockfileDirective, cargoLockfileDirective,
 		cratesPrefixDirective, procMacroOverrideDirective, allowUnusedCrateDirective,
 		rustFeatureDirective, defaultFeaturesDirective, defaultEditionDirective,
-		srcsGlobDirective}
+		srcsGlobDirective, ignoreImportDirective}
 }
 
 func (l *rustLang) GetConfig(c *config.Config) *rustConfig {
@@ -230,6 +237,7 @@ func (l *rustLang) Configure(c *config.Config, rel string, from *rule.File) {
 			DefaultFeatures:    true, // enable default features by default
 			DefaultEdition:     "",
 			SrcsGlob:           false,
+			IgnoredImports:     make(map[string]bool),
 		}
 	} else {
 		// NOTE(will): important to clone so that we don't leak state across directories
@@ -296,6 +304,8 @@ func (l *rustLang) Configure(c *config.Config, rel string, from *rule.File) {
 						directive.Key, directive.Key)
 				}
 				cfg.SrcsGlob = value
+			} else if directive.Key == ignoreImportDirective {
+				cfg.IgnoredImports[directive.Value] = true
 			}
 		}
 	}