Context for tooling logs (#190766)

## Summary
Allows to set context for the tooling logger. The context would be
logged before the log output, like so:

```
info [My-Tool] Hello!
```

Split from: https://github.com/elastic/kibana/pull/190401

---------

Co-authored-by: Tiago Costa <tiago.costa@elastic.co>

packages/kbn-dev-cli-runner/src/run.ts

@@ -31,18 +31,24 @@ export interface RunOptions {
   description?: string;
   log?: {
     defaultLevel?: LogLevel;
+    context?: string;
   };
   flags?: FlagOptions;
 }
 
 export async function run<T>(fn: RunFn<T>, options: RunOptions = {}): Promise<T | undefined> {
   const flags = getFlags(process.argv.slice(2), options.flags, options.log?.defaultLevel);
-  const log = new ToolingLog({
-    level: pickLevelFromFlags(flags, {
-      default: options.log?.defaultLevel,
-    }),
-    writeTo: process.stdout,
-  });
+  const log = new ToolingLog(
+    {
+      level: pickLevelFromFlags(flags, {
+        default: options.log?.defaultLevel,
+      }),
+      writeTo: process.stdout,
+    },
+    {
+      context: options.log?.context,
+    }
+  );
 
   const metrics = new Metrics(log);
   const helpText = getHelp({

packages/kbn-tooling-log/src/__snapshots__/tooling_log.test.ts.snap

@@ -9,6 +9,7 @@ Array [
         "bar",
         "baz",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "debug",
@@ -24,6 +25,7 @@ Array [
       "args": Array [
         [Error: error message],
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "error",
@@ -34,6 +36,7 @@ Array [
       "args": Array [
         "string message",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "error",
@@ -52,6 +55,7 @@ Array [
     "args": Array [
       "foo",
     ],
+    "context": undefined,
     "indent": 0,
     "source": undefined,
     "type": "debug",
@@ -60,6 +64,7 @@ Array [
     "args": Array [
       "bar",
     ],
+    "context": undefined,
     "indent": 0,
     "source": undefined,
     "type": "info",
@@ -68,6 +73,7 @@ Array [
     "args": Array [
       "baz",
     ],
+    "context": undefined,
     "indent": 0,
     "source": undefined,
     "type": "verbose",
@@ -81,6 +87,7 @@ Array [
     "args": Array [
       "foo",
     ],
+    "context": undefined,
     "indent": 0,
     "source": undefined,
     "type": "debug",
@@ -89,6 +96,7 @@ Array [
     "args": Array [
       "bar",
     ],
+    "context": undefined,
     "indent": 0,
     "source": undefined,
     "type": "info",
@@ -97,6 +105,7 @@ Array [
     "args": Array [
       "baz",
     ],
+    "context": undefined,
     "indent": 0,
     "source": undefined,
     "type": "verbose",
@@ -111,6 +120,7 @@ Array [
       "args": Array [
         "foo",
       ],
+      "context": undefined,
       "indent": 1,
       "source": undefined,
       "type": "debug",
@@ -121,6 +131,7 @@ Array [
       "args": Array [
         "bar",
       ],
+      "context": undefined,
       "indent": 3,
       "source": undefined,
       "type": "debug",
@@ -131,6 +142,7 @@ Array [
       "args": Array [
         "baz",
       ],
+      "context": undefined,
       "indent": 6,
       "source": undefined,
       "type": "debug",
@@ -141,6 +153,7 @@ Array [
       "args": Array [
         "box",
       ],
+      "context": undefined,
       "indent": 4,
       "source": undefined,
       "type": "debug",
@@ -151,6 +164,7 @@ Array [
       "args": Array [
         "foo",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "debug",
@@ -168,6 +182,7 @@ Array [
         "bar",
         "baz",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "info",
@@ -185,6 +200,7 @@ Array [
         "bar",
         "baz",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "success",
@@ -202,6 +218,7 @@ Array [
         "bar",
         "baz",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "verbose",
@@ -219,6 +236,7 @@ Array [
         "bar",
         "baz",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "warning",
@@ -236,6 +254,7 @@ Array [
         "bar",
         "baz",
       ],
+      "context": undefined,
       "indent": 0,
       "source": undefined,
       "type": "write",

packages/kbn-tooling-log/src/message.ts

@@ -20,4 +20,6 @@ export interface Message {
   source?: string;
   /** args passed to the logging method */
   args: any[];
+  /** an identifier of the logging entity */
+  context?: string;
 }

packages/kbn-tooling-log/src/tooling_log.ts

@@ -25,6 +25,13 @@ export interface ToolingLogOptions {
    * writers on either log will update the other too.
    */
   parent?: ToolingLog;
+
+  /**
+   * A string, conveniently the name of the script,
+   * that will be prepended to log messages.
+   * Can be useful to identify which entity is emitting the log.
+   */
+  context?: string;
 }
 
 export class ToolingLog implements SomeDevLog {
@@ -32,6 +39,7 @@ export class ToolingLog implements SomeDevLog {
   private writers$: Rx.BehaviorSubject<Writer[]>;
   private readonly written$: Rx.Subject<Message>;
   private readonly type: string | undefined;
+  private readonly context: string | undefined;
 
   constructor(writerConfig?: ToolingLogTextWriterConfig, options?: ToolingLogOptions) {
     this.indentWidth$ = options?.parent ? options.parent.indentWidth$ : new Rx.BehaviorSubject(0);
@@ -45,6 +53,7 @@ export class ToolingLog implements SomeDevLog {
 
     this.written$ = options?.parent ? options.parent.written$ : new Rx.Subject();
     this.type = options?.type;
+    this.context = options?.context;
   }
 
   /**
@@ -93,31 +102,31 @@ export class ToolingLog implements SomeDevLog {
   }
 
   public verbose(...args: any[]) {
-    this.sendToWriters('verbose', args);
+    this.sendToWriters({ type: 'verbose', context: this.context }, args);
   }
 
   public debug(...args: any[]) {
-    this.sendToWriters('debug', args);
+    this.sendToWriters({ type: 'debug', context: this.context }, args);
   }
 
   public info(...args: any[]) {
-    this.sendToWriters('info', args);
+    this.sendToWriters({ type: 'info', context: this.context }, args);
   }
 
   public success(...args: any[]) {
-    this.sendToWriters('success', args);
+    this.sendToWriters({ type: 'success', context: this.context }, args);
   }
 
   public warning(...args: any[]) {
-    this.sendToWriters('warning', args);
+    this.sendToWriters({ type: 'warning', context: this.context }, args);
   }
 
   public error(error: Error | string) {
-    this.sendToWriters('error', [error]);
+    this.sendToWriters({ type: 'error', context: this.context }, [error]);
   }
 
   public write(...args: any[]) {
-    this.sendToWriters('write', args);
+    this.sendToWriters({ type: 'write' }, args);
   }
 
   public getWriters() {
@@ -143,7 +152,7 @@ export class ToolingLog implements SomeDevLog {
     });
   }
 
-  private sendToWriters(type: MessageTypes, args: any[]) {
+  private sendToWriters({ type, context }: { type: MessageTypes; context?: string }, args: any[]) {
     const indent = this.indentWidth$.getValue();
     const writers = this.writers$.getValue();
     const msg: Message = {
@@ -151,6 +160,7 @@ export class ToolingLog implements SomeDevLog {
       indent,
       source: this.type,
       args,
+      context,
     };
 
     let written = false;

packages/kbn-tooling-log/src/tooling_log_collecting_writer.ts

@@ -26,16 +26,16 @@ export class ToolingLogCollectingWriter extends ToolingLogTextWriter {
   }
 
   /**
-   * Called by ToolingLog, extends messages with the source if message includes one.
+   * Called by ToolingLog, extends messages with the source and context if message include it.
    */
   write(msg: Message) {
-    if (msg.source) {
-      return super.write({
-        ...msg,
-        args: [`source[${msg.source}]`, ...msg.args],
-      });
-    }
+    const args = [
+      msg.source ? `source[${msg.source}]` : null,
+      msg.context ? `context[${msg.context}]` : null,
+    ]
+      .filter(Boolean)
+      .concat(msg.args);
 
-    return super.write(msg);
+    return super.write({ ...msg, args });
   }
 }

packages/kbn-tooling-log/src/tooling_log_text_writer.ts

@@ -103,7 +103,8 @@ export class ToolingLogTextWriter implements Writer {
       }
     }
 
-    const prefix = has(MSG_PREFIXES, msg.type) ? MSG_PREFIXES[msg.type] : '';
+    let prefix = has(MSG_PREFIXES, msg.type) ? MSG_PREFIXES[msg.type] : '';
+    prefix = msg.context ? prefix + `[${msg.context}] ` : prefix;
     ToolingLogTextWriter.write(this.writeTo, prefix, msg);
     return true;
   }