Audit visibility throughout the code.

- Reduce things from public to internal if they don't need to be
  public, like tests.
- Use fileprivate, not private, at file scope.
- Reduce some things that were internal to fileprivate or private.
- Remove @testable imports as a prerequisite for adding CI, making
  necessary decls public to access them.
- Some other random NFC cleanup.

Author: allevato

Sources/SwiftFormatConfiguration/Configuration.swift

@@ -14,7 +14,7 @@ import Foundation
 
 /// A version number that can be specified in the configuration file, which allows us to change the
 /// format in the future if desired and still support older files.
-private let highestSupportedConfigurationVersion = 1
+fileprivate let highestSupportedConfigurationVersion = 1
 
 /// Holds the complete set of configured values and defaults.
 public struct Configuration: Codable, Equatable {

Sources/SwiftFormatCore/Rule.swift

@@ -22,7 +22,7 @@ public protocol Rule {
   init(context: Context)
 }
 
-private var nameCache = [ObjectIdentifier: String]()
+fileprivate var nameCache = [ObjectIdentifier: String]()
 
 extension Rule {
   /// By default, the `ruleName` is just the name of the implementing rule class.

Sources/SwiftFormatCore/RuleMask.swift

@@ -86,7 +86,7 @@ extension SourceRange {
 /// The rule status comment directives implementation intentionally supports exactly the same nodes
 /// as `TokenStreamCreator` to disable pretty printing. This ensures ignore comments for pretty
 /// printing and for rules are as consistent as possible.
-private class RuleStatusCollectionVisitor: SyntaxVisitor {
+fileprivate class RuleStatusCollectionVisitor: SyntaxVisitor {
   /// Describes the possible matches for ignore directives, in comments.
   enum RuleStatusDirectiveMatch {
     /// There is a directive that applies to all rules.

Sources/SwiftFormatPrettyPrint/Comment.swift

@@ -40,7 +40,7 @@ struct Comment {
 
   let kind: Kind
   var text: [String]
-  public var length: Int
+  var length: Int
 
   init(kind: Kind, text: String) {
     self.kind = kind

Sources/SwiftFormatPrettyPrint/PrettyPrint.swift

@@ -779,12 +779,12 @@ public class PrettyPrinter {
 
 extension Diagnostic.Message {
 
-  static let moveEndOfLineComment = Diagnostic.Message(
+  public static let moveEndOfLineComment = Diagnostic.Message(
     .warning, "move end-of-line comment that exceeds the line length")
 
-  static let addTrailingComma = Diagnostic.Message(
+  public static let addTrailingComma = Diagnostic.Message(
     .warning, "add trailing comma to the last element in multiline collection literal")
 
-  static let removeTrailingComma = Diagnostic.Message(
+  public static let removeTrailingComma = Diagnostic.Message(
     .warning, "remove trailing comma from the last element in single line collection literal")
 }

Sources/SwiftFormatPrettyPrint/Token.swift

@@ -10,10 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import SwiftFormatConfiguration
-import SwiftFormatCore
-import SwiftSyntax
-
 enum GroupBreakStyle {
   /// A consistent break indicates that the break will always be finalized as a newline
   /// if wrapping occurs.

Sources/SwiftFormatPrettyPrint/TokenStreamCreator.swift

@@ -17,7 +17,7 @@ import SwiftSyntax
 
 /// Visits the nodes of a syntax tree and constructs a linear stream of formatting tokens that
 /// tell the pretty printer how the source text should be laid out.
-private final class TokenStreamCreator: SyntaxVisitor {
+fileprivate final class TokenStreamCreator: SyntaxVisitor {
   private var tokens = [Token]()
   private var beforeMap = [TokenSyntax: [Token]]()
   private var afterMap = [TokenSyntax: [[Token]]]()
@@ -3205,7 +3205,7 @@ extension TriviaPiece {
 /// Returns whether the given trivia includes a directive to ignore formatting for the next node.
 ///
 /// - Parameter trivia: Leading trivia for a node that the formatter supports ignoring.
-private func isFormatterIgnorePresent(inTrivia trivia: Trivia) -> Bool {
+fileprivate func isFormatterIgnorePresent(inTrivia trivia: Trivia) -> Bool {
   func isFormatterIgnore(in commentText: String, prefix: String, suffix: String) -> Bool {
     let trimmed =
       commentText.dropFirst(prefix.count)
@@ -3237,7 +3237,7 @@ private func isFormatterIgnorePresent(inTrivia trivia: Trivia) -> Bool {
 /// be safely ignored.
 ///
 /// - Parameter node: A node that can be safely ignored.
-private func shouldFormatterIgnore(node: Syntax) -> Bool {
+fileprivate func shouldFormatterIgnore(node: Syntax) -> Bool {
   // Regardless of the level of nesting, if the ignore directive is present on the first token
   // contained within the node then the entire node is eligible for ignoring.
   if let firstTrivia = node.firstToken?.leadingTrivia {

Sources/SwiftFormatRules/AddModifierRewriter.swift

@@ -10,12 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Foundation
 import SwiftFormatCore
 import SwiftSyntax
 
-private final class AddModifierRewriter: SyntaxRewriter {
-  let modifierKeyword: DeclModifierSyntax
+fileprivate final class AddModifierRewriter: SyntaxRewriter {
+  private let modifierKeyword: DeclModifierSyntax
 
   init(modifierKeyword: DeclModifierSyntax) {
     self.modifierKeyword = modifierKeyword
@@ -162,7 +161,7 @@ private final class AddModifierRewriter: SyntaxRewriter {
   /// this method does nothing and returns the given node as-is.
   /// - Parameter node: A node that was updated to include a new modifier.
   /// - Parameter modifiersProvider: A closure that returns all modifiers for the given node.
-  func nodeByRelocatingTrivia<NodeType: DeclSyntaxProtocol>(
+  private func nodeByRelocatingTrivia<NodeType: DeclSyntaxProtocol>(
     in node: NodeType,
     for modifiersProvider: (NodeType) -> ModifierListSyntax?
   ) -> NodeType {

Sources/SwiftFormatRules/AllPublicDeclarationsHaveDocumentation.swift

@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Foundation
 import SwiftFormatCore
 import SwiftSyntax
 
@@ -65,7 +64,7 @@ public final class AllPublicDeclarationsHaveDocumentation: SyntaxLintRule {
     return .skipChildren
   }
 
-  func diagnoseMissingDocComment(
+  private func diagnoseMissingDocComment(
     _ decl: DeclSyntax,
     name: String,
     modifiers: ModifierListSyntax?
@@ -83,7 +82,7 @@ public final class AllPublicDeclarationsHaveDocumentation: SyntaxLintRule {
 }
 
 extension Diagnostic.Message {
-  static func declRequiresComment(_ name: String) -> Diagnostic.Message {
+  public static func declRequiresComment(_ name: String) -> Diagnostic.Message {
     return .init(.warning, "add a documentation comment for '\(name)'")
   }
 }

Sources/SwiftFormatRules/AlwaysUseLowerCamelCase.swift

@@ -10,7 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Foundation
 import SwiftFormatCore
 import SwiftSyntax
 
@@ -41,7 +40,7 @@ public final class AlwaysUseLowerCamelCase: SyntaxLintRule {
     return .skipChildren
   }
 
-  func diagnoseLowerCamelCaseViolations(_ identifier: TokenSyntax) {
+  private func diagnoseLowerCamelCaseViolations(_ identifier: TokenSyntax) {
     guard case .identifier(let text) = identifier.tokenKind else { return }
     if text.isEmpty { return }
     if text.dropFirst().contains("_") || ("A"..."Z").contains(text.first!) {
@@ -53,7 +52,7 @@ public final class AlwaysUseLowerCamelCase: SyntaxLintRule {
 }
 
 extension Diagnostic.Message {
-  static func variableNameMustBeLowerCamelCase(_ name: String) -> Diagnostic.Message {
+  public static func variableNameMustBeLowerCamelCase(_ name: String) -> Diagnostic.Message {
     return .init(.warning, "rename variable '\(name)' using lower-camel-case")
   }
 }