From 85b24478f349fbc17e09d0be00c845393b0dacbb Mon Sep 17 00:00:00 2001
From: Connor Kirkpatrick <ckp@amazon.com>
Date: Wed, 23 Apr 2025 16:55:52 +0100
Subject: [PATCH 1/2] fix(logger): Format the stack trace as an array of
 strings in dev mode

When POWERTOOLS_DEV is enabled, the stack trace will be split on newline characters to create an array. This improves readability compared to a single long string
---
 packages/logger/src/formatter/LogFormatter.ts |  7 ++++++
 .../tests/unit/initializeLogger.test.ts       | 23 +++++++++++++++++++
 .../logger/tests/unit/workingWithkeys.test.ts |  6 ++---
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/packages/logger/src/formatter/LogFormatter.ts b/packages/logger/src/formatter/LogFormatter.ts
index 27af856835..7bea010289 100644
--- a/packages/logger/src/formatter/LogFormatter.ts
+++ b/packages/logger/src/formatter/LogFormatter.ts
@@ -131,6 +131,13 @@ abstract class LogFormatter {
       }
     }
 
+    if (
+      this.envVarsService?.isDevMode() &&
+      typeof formattedError.stack === 'string'
+    ) {
+      formattedError.stack = formattedError.stack.split('\n');
+    }
+
     return formattedError;
   }
 
diff --git a/packages/logger/tests/unit/initializeLogger.test.ts b/packages/logger/tests/unit/initializeLogger.test.ts
index 689c954493..e133ae71f0 100644
--- a/packages/logger/tests/unit/initializeLogger.test.ts
+++ b/packages/logger/tests/unit/initializeLogger.test.ts
@@ -163,4 +163,27 @@ describe('Log levels', () => {
 
     vi.useRealTimers();
   });
+
+  it('splits the stack trace into an array when POWERTOOLS_DEV is set', () => {
+    // Prepare
+    const logger = new Logger();
+    const err = new Error('Hello, world!');
+
+    // Act
+    logger.error('Error occured', err);
+
+    // Assess
+    expect(console.error).toHaveBeenCalledTimes(1);
+    expect(console.error).toHaveLoggedNth(
+      1,
+      expect.objectContaining({
+        error: {
+          location: expect.any(String),
+          message: 'Hello, world!',
+          name: 'Error',
+          stack: expect.any(Array),
+        },
+      })
+    );
+  });
 });
diff --git a/packages/logger/tests/unit/workingWithkeys.test.ts b/packages/logger/tests/unit/workingWithkeys.test.ts
index 94c388fc55..e4d4bbc1ec 100644
--- a/packages/logger/tests/unit/workingWithkeys.test.ts
+++ b/packages/logger/tests/unit/workingWithkeys.test.ts
@@ -56,7 +56,7 @@ describe('Working with keys', () => {
           location: expect.any(String),
           message: 'Something happened!',
           name: 'Error',
-          stack: expect.any(String),
+          stack: expect.any(Array),
         },
       },
       info: 'adds the message and error',
@@ -72,7 +72,7 @@ describe('Working with keys', () => {
           location: expect.any(String),
           message: 'Something happened!',
           name: 'Error',
-          stack: expect.any(String),
+          stack: expect.any(Array),
         },
       },
       info: 'adds the message and custom error',
@@ -104,7 +104,7 @@ describe('Working with keys', () => {
               location: expect.any(String),
               message: 'Arbitrary object error',
               name: 'Error',
-              stack: expect.any(String),
+              stack: expect.any(Array),
             },
           },
         },

From dc238e1b65f1b564c3404ad424564ef7ab13166b Mon Sep 17 00:00:00 2001
From: Connor Kirkpatrick <ckp@amazon.com>
Date: Wed, 23 Apr 2025 17:35:15 +0100
Subject: [PATCH 2/2] Incorporate feedback

---
 packages/logger/src/formatter/LogFormatter.ts | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/packages/logger/src/formatter/LogFormatter.ts b/packages/logger/src/formatter/LogFormatter.ts
index 7bea010289..9b9eea671a 100644
--- a/packages/logger/src/formatter/LogFormatter.ts
+++ b/packages/logger/src/formatter/LogFormatter.ts
@@ -116,7 +116,10 @@ abstract class LogFormatter {
       name,
       location: this.getCodeLocation(error.stack),
       message,
-      stack,
+      stack:
+        this.envVarsService?.isDevMode() && typeof stack === 'string'
+          ? stack?.split('\n')
+          : stack,
       cause:
         error.cause instanceof Error
           ? this.formatError(error.cause)
@@ -131,13 +134,6 @@ abstract class LogFormatter {
       }
     }
 
-    if (
-      this.envVarsService?.isDevMode() &&
-      typeof formattedError.stack === 'string'
-    ) {
-      formattedError.stack = formattedError.stack.split('\n');
-    }
-
     return formattedError;
   }