Fix configuration parsing error in `unused_declaration` rule (#4619)

CHANGELOG.md

@@ -34,6 +34,10 @@
 
 #### Bug Fixes
 
+* Fix configuration parsing error in `unused_declaration` rule.  
+  [SimplyDanny](https://github.com/SimplyDanny)
+  [#4612](https://github.com/realm/SwiftLint/issues/4612)
+
 * Fix false positives in `empty_enum_arguments` when the called expression
   is an identifier or an init call.  
   [Steffen Matthischke](https://github.com/heeaad)

Source/SwiftLintFramework/Rules/RuleConfigurations/UnusedDeclarationConfiguration.swift

@@ -32,7 +32,7 @@ struct UnusedDeclarationConfiguration: RuleConfiguration, Equatable {
             }
             switch (key, value) {
             case (.severity, let stringValue as String):
-                try severityConfiguration.apply(configuration: [key: stringValue])
+                try severityConfiguration.apply(configuration: stringValue)
             case (.includePublicAndOpen, let boolValue as Bool):
                 includePublicAndOpen = boolValue
             case (.relatedUSRsToSkip, let value):

Tests/SwiftLintFrameworkTests/UnusedDeclarationConfigurationTests.swift

@@ -0,0 +1,23 @@
+@testable import SwiftLintFramework
+import XCTest
+
+class UnusedDeclarationConfigurationTests: XCTestCase {
+    func testParseConfiguration() throws {
+        var testee = UnusedDeclarationConfiguration(
+            severity: .warning,
+            includePublicAndOpen: false,
+            relatedUSRsToSkip: []
+        )
+        let config: Any = [
+            "severity": "error",
+            "include_public_and_open": true,
+            "related_usrs_to_skip": ["a", "b"]
+        ]
+
+        try testee.apply(configuration: config)
+
+        XCTAssertEqual(testee.severityConfiguration.severity, .error)
+        XCTAssertTrue(testee.includePublicAndOpen)
+        XCTAssertEqual(testee.relatedUSRsToSkip, ["a", "b"])
+    }
+}