Improve 'Unknown key' parse error message

Author: nikitabobko

Sources/AppBundle/config/parseConfig.swift

@@ -336,6 +336,13 @@ indirect enum TomlBacktrace: CustomStringConvertible, Equatable {
         }
     }
 
+    var isRootKey: Bool {
+        return switch self {
+            case .rootKey: true
+            default: false
+        }
+    }
+
     static func + (lhs: TomlBacktrace, rhs: TomlBacktrace) -> TomlBacktrace {
         if case .emptyRoot = lhs {
             if case .key(let newRoot) = rhs {
@@ -372,7 +379,7 @@ extension TOMLTable {
 }
 
 func unknownKeyError(_ backtrace: TomlBacktrace) -> TomlParseError {
-    .semantic(backtrace, "Unknown key")
+    .semantic(backtrace, backtrace.isRootKey ? "Unknown top-level key" : "Unknown key")
 }
 
 func expectedActualTypeError(expected: TOMLType, actual: TOMLType, _ backtrace: TomlBacktrace) -> TomlParseError {

Sources/AppBundleTests/config/ConfigTest.swift

@@ -105,7 +105,7 @@ final class ConfigTest: XCTestCase {
         assertEquals(config.preservedWorkspaceNames.sorted(), ["1", "2", "3", "4"])
     }
 
-    func testUnknownKeyParseError() {
+    func testUnknownTopLevelKeyParseError() {
         let (config, errors) = parseConfig(
             """
             unknownKey = true
@@ -114,7 +114,22 @@ final class ConfigTest: XCTestCase {
         )
         assertEquals(
             errors.descriptions,
-            ["unknownKey: Unknown key"],
+            ["unknownKey: Unknown top-level key"],
+        )
+        assertEquals(config.enableNormalizationFlattenContainers, false)
+    }
+
+    func testUnknownKeyParseError() {
+        let (config, errors) = parseConfig(
+            """
+            enable-normalization-flatten-containers = false
+            [gaps]
+                unknownKey = true
+            """,
+        )
+        assertEquals(
+            errors.descriptions,
+            ["gaps.unknownKey: Unknown key"],
         )
         assertEquals(config.enableNormalizationFlattenContainers, false)
     }