From 327fb454652b3d240d74ec96a5ab38c06abe7320 Mon Sep 17 00:00:00 2001
From: Moritz Lang <hi@slashmo.codes>
Date: Tue, 6 Apr 2021 12:40:15 +0200
Subject: [PATCH] Include source in StreamLogHandler output

Motivation:

When using the same Logger across an application in combination
with the default StreamLogHandler, it may be difficult to differentiate
between logs produced by different modules. ServiceLifecycle works around
this by prepending the log message with [Lifecycle], which is what I'd like
to do StreamLogHandler by default, leveraging the source log parameter.

Modifications:

StreamLogHandler will include the source in brackets right before
the log message when writing a log.

Result:

Logs from different modules are easily differentiable when produced
using the same Logger instance.
---
 Sources/Logging/Logging.swift        |  2 +-
 Tests/LoggingTests/LoggingTest.swift | 10 ++++++----
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/Sources/Logging/Logging.swift b/Sources/Logging/Logging.swift
index e76c68b3..fec15160 100644
--- a/Sources/Logging/Logging.swift
+++ b/Sources/Logging/Logging.swift
@@ -917,7 +917,7 @@ public struct StreamLogHandler: LogHandler {
             : self.prettify(self.metadata.merging(metadata!, uniquingKeysWith: { _, new in new }))
 
         var stream = self.stream
-        stream.write("\(self.timestamp()) \(level) \(self.label) :\(prettyMetadata.map { " \($0)" } ?? "") \(message)\n")
+        stream.write("\(self.timestamp()) \(level) \(self.label) :\(prettyMetadata.map { " \($0)" } ?? "") [\(source)] \(message)\n")
     }
 
     private func prettify(_ metadata: Logger.Metadata) -> String? {
diff --git a/Tests/LoggingTests/LoggingTest.swift b/Tests/LoggingTests/LoggingTest.swift
index e1d2817f..f064fffa 100644
--- a/Tests/LoggingTests/LoggingTest.swift
+++ b/Tests/LoggingTests/LoggingTest.swift
@@ -669,12 +669,13 @@ class LoggingTest: XCTestCase {
         LoggingSystem.bootstrapInternal { _ in
             StreamLogHandler(label: label, stream: interceptStream)
         }
+        let source = "testSource"
         let log = Logger(label: label)
 
         let testString = "my message is better than yours"
-        log.critical("\(testString)")
+        log.critical("\(testString)", source: source)
 
-        let pattern = "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}(\\+|-)\\d{4}\\s\(Logger.Level.critical)\\s\(label)\\s:\\s\(testString)$"
+        let pattern = "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}(\\+|-)\\d{4}\\s\(Logger.Level.critical)\\s\(label)\\s:\\s\\[\(source)\\]\\s\(testString)$"
 
         let messageSucceeded = interceptStream.interceptedText?.trimmingCharacters(in: .whitespacesAndNewlines).range(of: pattern, options: .regularExpression) != nil
 
@@ -688,12 +689,13 @@ class LoggingTest: XCTestCase {
         LoggingSystem.bootstrapInternal { _ in
             StreamLogHandler(label: label, stream: interceptStream)
         }
+        let source = "testSource"
         let log = Logger(label: label)
 
         let testString = "my message is better than yours"
-        log.critical("\(testString)", metadata: ["test": "test"])
+        log.critical("\(testString)", metadata: ["test": "test"], source: source)
 
-        let pattern = "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}(\\+|-)\\d{4}\\s\(Logger.Level.critical)\\s\(label)\\s:\\stest=test\\s\(testString)$"
+        let pattern = "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}(\\+|-)\\d{4}\\s\(Logger.Level.critical)\\s\(label)\\s:\\stest=test\\s\\[\(source)\\]\\s\(testString)$"
 
         let messageSucceeded = interceptStream.interceptedText?.trimmingCharacters(in: .whitespacesAndNewlines).range(of: pattern, options: .regularExpression) != nil