Handle non-string logged content with trace ID injection (#186)

* Use util.inspect to get string repr for non-string log content

* Add unit test to check that logging objects works as expected

Author: swfunc

src/trace/patch-console.spec.ts

@@ -82,6 +82,14 @@ describe("patchConsole", () => {
     cnsole.log();
     expect(log).toHaveBeenCalledWith("[dd.trace_id=123456 dd.span_id=78910]");
   });
+  it("injects trace context into logged object message", () => {
+    patchConsole(cnsole as any, contextService);
+
+    cnsole.log({ objectKey: "objectValue", otherObjectKey: "otherObjectValue" });
+    expect(log).toHaveBeenCalledWith(
+      "[dd.trace_id=123456 dd.span_id=78910] { objectKey: 'objectValue', otherObjectKey: 'otherObjectValue' }",
+    );
+  });
   it("leaves empty message unmodified when there is no trace context", () => {
     contextService.rootTraceContext = undefined;
     patchConsole(cnsole as any, contextService);

src/trace/patch-console.ts

@@ -1,4 +1,5 @@
 import * as shimmer from "shimmer";
+import { inspect } from "util";
 
 import { getLogLevel, LogLevel, setLogLevel } from "../utils/log";
 import { TraceContextService } from "./trace-context-service";
@@ -58,7 +59,14 @@ function patchMethod(mod: Console, method: LogMethod, contextService: TraceConte
             arguments.length = 1;
             arguments[0] = prefix;
           } else {
-            arguments[0] = `${prefix} ${arguments[0]}`;
+            let logContent = arguments[0];
+
+            // If what's being logged is not a string, use util.inspect to get a str representation
+            if (typeof logContent !== "string") {
+              logContent = inspect(logContent);
+            }
+
+            arguments[0] = `${prefix} ${logContent}`;
           }
         }
       } catch (error) {