fix: treat ignored packages as used on the workspace level (#295)

If a workspace member marks an unused dependency as ignored, cargo-shear
will still try to remove it on the workspace level. Any subsequent build
will fail as the workspace member now tries to inherit a dependency that
no longer exists.

A failing test case was added in this commit:
0e3a656

Author: scootermon

src/package_processor.rs

@@ -104,8 +104,12 @@ impl PackageProcessor {
         let module_names_from_package_deps: FxHashSet<String> =
             package_dependency_names_map.keys().cloned().collect();
 
-        let package_dependency_names: FxHashSet<String> =
-            package_dependency_names_map.values().cloned().collect();
+        // Add ignored names to the set of package dependency names to prevent them from being marked unused in the workspace analysis.
+        let package_dependency_names: FxHashSet<String> = package_dependency_names_map
+            .values()
+            .cloned()
+            .chain(package_ignored_names.into_iter().map(str::to_string))
+            .collect();
 
         let module_names_from_rust_files = self.analyzer.analyze_package(package)?;
 

tests/fixtures/workspace_unused_deps/Cargo.lock

@@ -8,3 +8,5 @@ serde = "1.0"
 unused-crate = "0.1"
 # Used by app
 clap = "4.0"
+# Ignored by app - should still be considered used
+humantime-serde = "0.1"

tests/fixtures/workspace_unused_deps/Cargo.toml

@@ -3,6 +3,10 @@ name = "app"
 version = "0.1.0"
 edition = "2021"
 
+[package.metadata.cargo-shear]
+ignored = ["humantime-serde"]
+
 [dependencies]
 clap = { workspace = true }
 lib = { path = "../lib" }
+humantime-serde = { workspace = true }

tests/fixtures/workspace_unused_deps/app/Cargo.toml

@@ -93,6 +93,8 @@ fn test_workspace_unused_deps_fix() {
     // serde and clap should still be there (they're used)
     assert!(cargo_toml.contains("serde"), "Used workspace dependency should remain");
     assert!(cargo_toml.contains("clap"), "Used workspace dependency should remain");
+    // humantime-serde should still be there (it's ignored in app)
+    assert!(cargo_toml.contains("humantime-serde"), "Used workspace dependency should remain");
 
     // unused-crate should be removed (it's not used by anyone)
     assert!(!cargo_toml.contains("unused-crate"), "Unused workspace dependency should be removed");