Auto detect log format

.changesets/auto-detect-log-format.md

@@ -0,0 +1,11 @@
+---
+bump: patch
+type: change
+---
+
+Detect the log format automatically. We now detect if a log line is in the JSON, Logfmt, or plaintext format. No further config needed when calling our logger, like so: 
+
+```javascript
+const logger = Appsignal.logger("app");
+logger.info("message");
+```

src/__tests__/logger.test.ts

@@ -52,19 +52,19 @@ describe("BaseLogger", () => {
     ).toEqual(6)
   })
 
-  it("defaults to a plaintext logger format", () => {
-    expect(logger.format).toEqual(0)
+  it("defaults to the autodetect logger format", () => {
+    expect(logger.format).toEqual(3)
     expect(client.internalLogger.warn).not.toHaveBeenCalled()
   })
 
-  it("sets a plaintext format level when the format is unknown and logs a warning", () => {
+  it("sets the autodetect format level when the format is unknown and logs a warning", () => {
     logger = new BaseLogger(
       client,
       "groupname",
       "trace" as LoggerLevel,
       "bacon" as LoggerFormat
     )
-    expect(logger.format).toEqual(0)
+    expect(logger.format).toEqual(3)
     expect(client.internalLogger.warn).toHaveBeenCalledWith(
       expect.stringContaining(`"bacon"`)
     )
@@ -80,6 +80,9 @@ describe("BaseLogger", () => {
     expect(new BaseLogger(client, "groupname", "trace", "json").format).toEqual(
       2
     )
+    expect(
+      new BaseLogger(client, "groupname", "trace", "autodetect").format
+    ).toEqual(3)
   })
 
   it("logs to the extension if at or above the logger level", () => {
@@ -96,28 +99,28 @@ describe("BaseLogger", () => {
     expect(client.extension.log).toHaveBeenCalledWith(
       "groupname",
       3,
-      0,
+      3,
       "info message",
       attributes
     )
     expect(client.extension.log).toHaveBeenCalledWith(
       "groupname",
       4,
-      0,
+      3,
       "log message",
       attributes
     )
     expect(client.extension.log).toHaveBeenCalledWith(
       "groupname",
       5,
-      0,
+      3,
       "warn message",
       attributes
     )
     expect(client.extension.log).toHaveBeenCalledWith(
       "groupname",
       6,
-      0,
+      3,
       "error message",
       attributes
     )

src/client.ts

@@ -144,7 +144,7 @@ export class Client {
   static logger(
     group: string,
     level: LoggerLevel = "info",
-    format: LoggerFormat = "plaintext"
+    format: LoggerFormat = "autodetect"
   ): Logger {
     if (this.client) {
       return this.client.logger(group, level, format)

src/logger.ts

@@ -19,12 +19,13 @@ function severity(level: LoggerLevel) {
   return LOGGER_LEVEL_SEVERITY[level] ?? UNKNOWN_SEVERITY
 }
 
-export type LoggerFormat = "plaintext" | "logfmt" | "json"
+export type LoggerFormat = "plaintext" | "logfmt" | "json" | "autodetect"
 
 export const LOGGER_FORMAT: Record<LoggerFormat, number> = {
   plaintext: 0,
   logfmt: 1,
-  json: 2
+  json: 2,
+  autodetect: 3
 }
 
 const UNKNOWN_FORMAT = -1
@@ -52,7 +53,7 @@ export class BaseLogger implements Logger {
     client: Client,
     group: string,
     level: LoggerLevel = "info",
-    format: LoggerFormat = "plaintext"
+    format: LoggerFormat = "autodetect"
   ) {
     if (typeof group != "string") {
       throw new TypeError(
@@ -75,10 +76,10 @@ export class BaseLogger implements Logger {
 
     if (this.format == UNKNOWN_FORMAT) {
       this.#client.internalLogger.warn(
-        `Logger format must be "plaintext", "logfmt", or "json", ` +
-          `but "${format}" was given. Logger format set to "plaintext".`
+        `Logger format must be "plaintext", "logfmt", "json", or "autodetect", ` +
+          `but "${format}" was given. Logger format set to "autodetect".`
       )
-      this.format = 0
+      this.format = 3
     }
   }