Accept more Objective-C symbol graph identifiers

Accept "objective-c" and "c" as interface language identifiers in symbol
graph files emitted by clang.

rdar://90361614

Sources/SwiftDocC/Model/SourceLanguage.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -14,14 +14,18 @@ public struct SourceLanguage: Hashable, Codable {
     public var name: String
     /// A globally unique identifier for the language.
     public var id: String
+    /// Aliases for the language's identifier.
+    public var idAliases: [String] = []
 
     /// Creates a new language with a given name and identifier.
     /// - Parameters:
     ///   - name: The display name of the programming language.
     ///   - id: A globally unique identifier for the language.
-    public init(name: String, id: String) {
+    ///   - idAliases: Aliases for the language's identifier.
+    public init(name: String, id: String, idAliases: [String] = []) {
         self.name = name
         self.id = id
+        self.idAliases = idAliases
     }
 
     /// Finds the programming language that matches a given query identifier.
@@ -34,7 +38,7 @@ public struct SourceLanguage: Hashable, Codable {
         switch queryID {
         case "swift":
             self = .swift
-        case "occ":
+        case "occ", "objective-c", "c":
             self = .objectiveC
         case "javascript":
             self = .javaScript
@@ -52,7 +56,7 @@ public struct SourceLanguage: Hashable, Codable {
     public init(id: String) {
         switch id {
         case "swift": self = .swift
-        case "occ": self = .objectiveC
+        case "occ", "objective-c", "c": self = .objectiveC
         case "javascript": self = .javaScript
         case "data": self = .data
         case "metal": self = .metal
@@ -101,17 +105,30 @@ public struct SourceLanguage: Hashable, Codable {
     }
 
     private static func firstKnownLanguage(withName name: String) -> SourceLanguage? {
-        return SourceLanguage.knownLanguages.first { $0.name.lowercased() == name.lowercased() }
+        SourceLanguage.knownLanguages.first { $0.name.lowercased() == name.lowercased() }
     }
 
     private static func firstKnownLanguage(withIdentifier id: String) -> SourceLanguage? {
-        return SourceLanguage.knownLanguages.first { $0.id.lowercased() == id.lowercased() }
+        SourceLanguage.knownLanguages.first { knownLanguage in
+            ([knownLanguage.id] + knownLanguage.idAliases)
+                .map { $0.lowercased() }
+                .contains(id)
+        }
     }
 
     /// The Swift programming language.
     public static let swift = SourceLanguage(name: "Swift", id: "swift")
+
     /// The Objective-C programming language.
-    public static let objectiveC = SourceLanguage(name: "Objective-C", id: "occ")
+    public static let objectiveC = SourceLanguage(
+        name: "Objective-C",
+        id: "occ",
+        idAliases: [
+            "objective-c",
+            "c", // FIXME: DocC should display C as its own language (SR-16050).
+        ]
+    )
+
     /// The JavaScript programming language or another language that conforms to the ECMAScript specification.
     public static let javaScript = SourceLanguage(name: "JavaScript", id: "javascript")
     /// Miscellaneous data, that's not a programming language.

Sources/SwiftDocC/Semantics/Symbol/DocumentationDataVariants+SymbolGraphSymbol.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -23,7 +23,7 @@ extension DocumentationDataVariants {
                     guard selector.platform == platformName else { return nil }
 
                     return (
-                        DocumentationDataVariantsTrait(interfaceLanguage: selector.interfaceLanguage),
+                        DocumentationDataVariantsTrait(for: selector),
                         transform(value)
                     )
                 }
@@ -44,7 +44,7 @@ extension DocumentationDataVariants {
                     else { return nil }
 
                     return (
-                        DocumentationDataVariantsTrait(interfaceLanguage: selector.interfaceLanguage),
+                        DocumentationDataVariantsTrait(for: selector),
                         value
                     )
                 }

Sources/SwiftDocC/Semantics/Symbol/DocumentationDataVariants.swift

@@ -1,14 +1,15 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
  See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
 import Foundation
+import SymbolKit
 
 /// A model type that encapsulates variants of documentation node data.
 ///
@@ -141,4 +142,14 @@ public struct DocumentationDataVariantsTrait: Hashable {
     public init(interfaceLanguage: String? = nil) {
         self.interfaceLanguage = interfaceLanguage
     }
+
+    /// Creates a new trait given a symbol graph selector.
+    ///
+    /// - Parameter selector: The symbol graph selector to use when creating the trait.
+    public init(for selector: UnifiedSymbolGraph.Selector) {
+        self.init(
+            interfaceLanguage: SourceLanguage(knownLanguageIdentifier: selector.interfaceLanguage)?.id
+                ?? selector.interfaceLanguage
+        )
+    }
 }

Sources/SwiftDocC/Semantics/Symbol/Symbol.swift

@@ -303,7 +303,7 @@ extension Symbol {
     /// depending on variances in their implementation across platforms (e.g. use `NSPoint` vs `CGPoint` parameter in a method).
     /// This method finds matching symbols between graphs and merges their declarations in case there are differences.
     func mergeDeclaration(mergingDeclaration: SymbolGraph.Symbol.DeclarationFragments, identifier: String, symbolAvailability: SymbolGraph.Symbol.Availability?, selector: UnifiedSymbolGraph.Selector) throws {
-        let trait = DocumentationDataVariantsTrait(interfaceLanguage: selector.interfaceLanguage)
+        let trait = DocumentationDataVariantsTrait(for: selector)
         let platformName = selector.platform
 
         if let platformName = platformName,

Tests/SwiftDocCTests/Model/SemaToRenderNodeMultiLanguageTests.swift

@@ -1,7 +1,7 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2021 Apple Inc. and the Swift project authors
+ Copyright (c) 2021-2022 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See https://swift.org/LICENSE.txt for license information
@@ -76,9 +76,26 @@ class SemaToRenderNodeMixedLanguageTests: XCTestCase {
             )
         }
     }
-
-    func testOutputsMultiLanguageRenderNodes() throws {
-        let outputConsumer = try mixedLanguageFrameworkConsumer()
+
+    func assertOutputsMultiLanguageRenderNodes(variantInterfaceLanguage: String) throws {
+        let outputConsumer = try mixedLanguageFrameworkConsumer { bundleURL in
+            // Update the clang symbol graph with the Objective-C identifier given in variantInterfaceLanguage.
+
+            let clangSymbolGraphLocation = bundleURL
+                .appendingPathComponent("symbol-graphs")
+                .appendingPathComponent("clang")
+                .appendingPathComponent("MixedLanguageFramework.symbols.json")
+
+            var clangSymbolGraph = try JSONDecoder().decode(SymbolGraph.self, from: Data(contentsOf: clangSymbolGraphLocation))
+
+            clangSymbolGraph.symbols = clangSymbolGraph.symbols.mapValues { symbol in
+                var symbol = symbol
+                symbol.identifier.interfaceLanguage = variantInterfaceLanguage
+                return symbol
+            }
+
+            try JSONEncoder().encode(clangSymbolGraph).write(to: clangSymbolGraphLocation)
+        }
 
         XCTAssertEqual(
             Set(
@@ -136,7 +153,7 @@ class SemaToRenderNodeMixedLanguageTests: XCTestCase {
                 "c:@M@TestFramework@objc(pl)MixedLanguageProtocol(im)mixedLanguageMethod",
                 "c:@M@TestFramework@objc(cs)MixedLanguageClassConformingToProtocol(im)init",
                 "c:@CM@TestFramework@objc(cs)MixedLanguageClassConformingToProtocol(im)mixedLanguageMethod",
-
+                
                 "MixedLanguageProtocol Implementations",
                 "Article",
                 "APICollection",
@@ -146,7 +163,19 @@ class SemaToRenderNodeMixedLanguageTests: XCTestCase {
             ]
         )
     }
-
+
+    func testOutputsMultiLanguageRenderNodesWithOccIdentifier() throws {
+        try assertOutputsMultiLanguageRenderNodes(variantInterfaceLanguage: "occ")
+    }
+
+    func testOutputsMultiLanguageRenderNodesWithObjectiveCIdentifier() throws {
+        try assertOutputsMultiLanguageRenderNodes(variantInterfaceLanguage: "objective-c")
+    }
+
+    func testOutputsMultiLanguageRenderNodesWithCIdentifier() throws {
+        try assertOutputsMultiLanguageRenderNodes(variantInterfaceLanguage: "c")
+    }
+
     func testFrameworkRenderNodeHasExpectedContentAcrossLanguages() throws {
         let outputConsumer = try mixedLanguageFrameworkConsumer()
         let mixedLanguageFrameworkRenderNode = try outputConsumer.renderNode(

Tests/SwiftDocCTests/Model/SourceLanguageTests.swift

@@ -0,0 +1,19 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2022 Apple Inc. and the Swift project authors
+ Licensed under Apache License v2.0 with Runtime Library Exception
+
+ See https://swift.org/LICENSE.txt for license information
+ See https://swift.org/CONTRIBUTORS.txt for Swift project authors
+*/
+
+@testable import SwiftDocC
+import XCTest
+
+class SourceLanguageTests: XCTestCase {
+    func testUsesIDAliasesWhenQueryingFirstKnownLanguage() {
+        XCTAssertEqual(SourceLanguage(knownLanguageIdentifier: "objective-c"), .objectiveC)
+        XCTAssertEqual(SourceLanguage(knownLanguageIdentifier: "c"), .objectiveC)
+    }
+}

Tests/SwiftDocCTests/Semantics/DocumentationDataVariantsTests.swift

@@ -10,6 +10,7 @@
 
 import Foundation
 import XCTest
+import SymbolKit
 @testable import SwiftDocC
 
 class DocumentationDataVariantsTests: XCTestCase {
@@ -84,4 +85,16 @@ class DocumentationDataVariantsTests: XCTestCase {
         variants[objectiveCTrait] = "Objective-C"
         XCTAssertEqual(variants.firstValue, "Swift") // Swift is still treated as the default value.
     }
+
+    func testInitializesUsingSelectorLanguage() {
+        XCTAssertEqual(
+            DocumentationDataVariantsTrait(
+                for: UnifiedSymbolGraph.Selector(
+                    interfaceLanguage: "MyLanguage",
+                    platform: nil
+                )
+            ).interfaceLanguage,
+            "MyLanguage"
+        )
+    }
 }