WIP diagnostics

Author: Jesse Haigh

Sources/SwiftDocC/Checker/Checkers/InvalidCodeBlockOption.swift

@@ -0,0 +1,58 @@
+/*
+ This source file is part of the Swift.org open source project
+
+ Copyright (c) 2025 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
+*/
+
+public import Foundation
+public import Markdown
+
+/**
+ Code blocks can have a `nocopy` option after the \`\`\`, in the language line.
+`nocopy` can be immediately after the \`\`\` or after a specified language and a comma (`,`).
+ */
+public struct InvalidCodeBlockOption: Checker {
+    public var problems = [Problem]()
+
+    // FIXME: populate this from the parse options
+    /// Parsing options for code blocks
+    private let knownOptions = ["nocopy"]
+
+    private var sourceFile: URL?
+
+    /// Creates a new checker that detects documents with multiple titles.
+    ///
+    /// - Parameter sourceFile: The URL to the documentation file that the checker checks.
+    public init(sourceFile: URL?) {
+        self.sourceFile = sourceFile
+    }
+
+    public mutating func visitCodeBlock(_ codeBlock: CodeBlock) {
+        let info = codeBlock.language?.trimmingCharacters(in: .whitespacesAndNewlines) ?? ""
+        guard !info.isEmpty else { return }
+
+        let tokens = info
+            .split(separator: ",")
+            .map { $0.trimmingCharacters(in: .whitespaces) }
+            .filter { !$0.isEmpty }
+
+        guard !tokens.isEmpty else { return }
+
+        for token in tokens {
+            // if the token is an exact match, we don't need to do anything
+            guard !knownOptions.contains(token) else { continue }
+
+            let matches = NearMiss.bestMatches(for: knownOptions, against: token)
+
+            if !matches.isEmpty {
+                let diagnostic = Diagnostic(source: sourceFile, severity: .warning, range: codeBlock.range, identifier: "org.swift.docc.InvalidCodeBlockOption", summary: "Unknown option \(token) in code block. Did you mean \(matches)?", explanation: nil)
+                // FIXME: figure out the position of 'token' and provide solutions
+                problems.append(Problem(diagnostic: diagnostic, possibleSolutions: []))
+            }
+        }
+    }
+}

Sources/SwiftDocC/Infrastructure/DocumentationContext.swift

@@ -438,6 +438,7 @@ public class DocumentationContext {
             MissingAbstract(sourceFile: source).any(),
             NonOverviewHeadingChecker(sourceFile: source).any(),
             SeeAlsoInTopicsHeadingChecker(sourceFile: source).any(),
+            InvalidCodeBlockOption(sourceFile: source).any(),
         ])
         checker.visit(document)
         diagnosticEngine.emit(checker.problems)