Add a no-op shim for os.Logger

Sources/SwiftDocC/Utility/FoundationExtensions/NoOpSignposterShim.swift

@@ -8,7 +8,31 @@
  See https://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
-/// A shim for `OSSignposter` that does nothing, except for running the passed interval task.
+/// A shim for `os.Logger` that does nothing.
+///
+/// This type allows calling code to avoid using `#if canImport(os)` throughout the implementation.
+package struct NoOpLoggerShim : @unchecked Sendable {
+    package init() {}
+
+    package var isEnabled: Bool { false }
+
+    package enum Level {
+        case `default`, info, debug, error, fault
+    }
+
+    package func log(_ message: NoOpLogMessage) {}
+    package func log(level: Level, _ message: NoOpLogMessage) {}
+
+    package func trace(_ message: NoOpLogMessage) {}
+    package func debug(_ message: NoOpLogMessage) {}
+    package func info(_ message: NoOpLogMessage) {}
+    package func warning(_ message: NoOpLogMessage) {}
+    package func error(_ message: NoOpLogMessage) {}
+    package func critical(_ message: NoOpLogMessage) {}
+    package func fault(_ message: NoOpLogMessage) {}
+}
+
+/// A shim for `os.OSSignposter` that does nothing, except for running the passed interval task.
 ///
 /// This type allows calling code to avoid using `#if canImport(os)` throughout the implementation.
 package struct NoOpSignposterShim : @unchecked Sendable {

Tests/SwiftDocCTests/Utility/NoOpSignposterShimTests.swift

@@ -38,6 +38,8 @@ final class NoOpSignposterShimTests: XCTestCase {
     }
 
     func testCanAcceptMessageInputs() {
+        // Note: this test has no assertions.
+        // It simply verifies that the message interpolations compile
         let signposter = NoOpSignposterShim()
 
         let handle = signposter.beginInterval("Some interval", "Some message")
@@ -51,5 +53,17 @@ final class NoOpSignposterShimTests: XCTestCase {
         signposter.emitEvent("Some event", "Some non-secret string \("my secret", privacy: .public)")
 
         signposter.emitEvent("Some event", "Some aligned values \(12, align: .right(columns: 5)) \("some text", align: .left(columns: 10))")
+
+        let logger = NoOpLoggerShim()
+
+        logger.log("Some static string")
+        logger.info("Some formatted bool \(true, format: .answer)")
+        logger.debug("Some formatted integer \(12, format: .decimal)")
+        logger.error("Some formatted float \(7.0, format: .exponential)")
+        logger.fault("Some sensitive string \("my secret", privacy: .sensitive(mask: .hash))")
+        logger.log(level: .fault, "Some non-secret string \("my secret", privacy: .public)")
+
+        logger.log(level: .default, "Some aligned values \(12, align: .right(columns: 5)) \("some text", align: .left(columns: 10))")
+
     }
 }