Allow to customize Severity for formating rules

In order to check during CI for propper formatting,
it is now also possible to specify severity for
the formating rules.

Issue: swiftlang#879

Author: bkolb

Sources/SwiftFormat/API/FindingCategorizing.swift

@@ -17,13 +17,23 @@
 /// to be displayed as part of the diagnostic message when the finding is presented to the user.
 /// For example, the category `Indentation` in the message `[Indentation] Indent by 2 spaces`.
 public protocol FindingCategorizing: CustomStringConvertible {
-  /// The default severity of findings emitted in this category.
+  /// The severity of findings emitted in this category.
   ///
-  /// By default, all findings are warnings. Individual categories may choose to override this to
+  /// By default, all findings are warnings. Individual categories or configuration may choose to override this to
   /// make the findings in those categories more severe.
-  var defaultSeverity: Finding.Severity { get }
+  func severity(configuration: Configuration) -> Finding.Severity
+
+  /// The name of the category.
+  var name: String {get}
 }
 
 extension FindingCategorizing {
-  public var defaultSeverity: Finding.Severity { .warning }
+    func severity(configuration: Configuration) -> Finding.Severity {
+        return severityFromConfig(configuration: configuration)
+    }
+
+    func severityFromConfig(configuration: Configuration) -> Finding.Severity {
+        guard let customSeverity = configuration.ruleSeverity[self.name] else { return .warning }
+        return customSeverity.findingSeverity
+    }
 }

Sources/SwiftFormat/Core/FindingEmitter.swift

@@ -44,7 +44,8 @@ final class FindingEmitter {
     _ message: Finding.Message,
     category: FindingCategorizing,
     location: Finding.Location? = nil,
-    notes: [Finding.Note] = []
+    notes: [Finding.Note] = [],
+    context: Context
   ) {
     guard let consumer = self.consumer else { return }
 
@@ -54,7 +55,7 @@ final class FindingEmitter {
       Finding(
         category: category,
         message: message,
-        severity: category.defaultSeverity,
+        severity: category.severity(configuration: context.configuration),
         location: location,
         notes: notes
       )

Sources/SwiftFormat/Core/Rule.swift

@@ -93,17 +93,15 @@ extension Rule {
       message,
       category: category,
       location: syntaxLocation.flatMap(Finding.Location.init),
-      notes: notes
+      notes: notes,
+      context: context
     )
   }
 }
 
 extension Configuration {
   func findingSeverity(for rule: any Rule.Type) -> Finding.Severity? {
     guard let severity = self.ruleSeverity[rule.ruleName] else { return nil }
-    switch severity {
-      case .warning: return .warning
-      case .error: return .error
-    }
+    return severity.findingSeverity
   }
 }

Sources/SwiftFormat/Core/RuleBasedFindingCategory.swift

@@ -24,13 +24,20 @@ struct RuleBasedFindingCategory: FindingCategorizing {
 
   var severity: Finding.Severity?
 
-  public var defaultSeverity: Finding.Severity {
-    return severity ?? .warning
+  var name: String {
+    return description
   }
 
   /// Creates a finding category that wraps the given rule type.
   init(ruleType: Rule.Type, severity: Finding.Severity? = nil) {
     self.ruleType = ruleType
     self.severity = severity
   }
+
+  func severity(configuration: Configuration) -> Finding.Severity {
+    if let severity = severity {
+        return severity
+    }
+    return severityFromConfig(configuration: configuration)
+  }
 }

Sources/SwiftFormat/PrettyPrint/PrettyPrint.swift

@@ -819,7 +819,8 @@ public class PrettyPrinter {
     context.findingEmitter.emit(
       message,
       category: category,
-      location: Finding.Location(file: context.fileURL.path, line: outputBuffer.lineNumber, column: column)
+      location: Finding.Location(file: context.fileURL.path, line: outputBuffer.lineNumber, column: column),
+      context: context
     )
   }
 }

Sources/SwiftFormat/PrettyPrint/PrettyPrintFindingCategory.swift

@@ -12,6 +12,7 @@
 
 /// Categories for findings emitted by the pretty printer.
 enum PrettyPrintFindingCategory: FindingCategorizing {
+
   /// Finding related to an end-of-line comment.
   case endOfLineComment
 
@@ -24,4 +25,9 @@ enum PrettyPrintFindingCategory: FindingCategorizing {
     case .trailingComma: return "TrailingComma"
     }
   }
+
+  var name: String {
+    self.description
+  }
+
 }

Sources/SwiftFormat/PrettyPrint/WhitespaceFindingCategory.swift

@@ -44,4 +44,8 @@ enum WhitespaceFindingCategory: FindingCategorizing {
     case .lineLength: return "LineLength"
     }
   }
+
+  var name: String {
+    return self.description
+  }
 }

Sources/SwiftFormat/PrettyPrint/WhitespaceLinter.swift

@@ -380,7 +380,8 @@ public class WhitespaceLinter {
     context.findingEmitter.emit(
       message,
       category: category,
-      location: Finding.Location(sourceLocation)
+      location: Finding.Location(sourceLocation),
+      context: context
     )
   }