Add dev-mode ConsoleTransport for logger

src/observability/logger/console-transport.test.ts

@@ -0,0 +1,45 @@
+import { describe, expect, it, vi } from "vitest";
+import type { LogRecord } from "./types.js";
+import { ConsoleTransport } from "./console-transport.js";
+
+describe("ConsoleTransport", () => {
+  it("pipes debug records to console.debug", () => {
+    const spy = vi.spyOn(console, "debug").mockImplementation(() => {});
+    const transport = new ConsoleTransport();
+    const record: LogRecord = { ts: "2025-01-01T00:00:00Z", level: "debug", msg: "hello", fields: {} };
+    transport.write(record);
+    expect(spy).toHaveBeenCalledTimes(1);
+    expect(spy.mock.calls[0]?.[0]).toContain("hello");
+    spy.mockRestore();
+  });
+
+  it("pipes info records to console.info", () => {
+    const spy = vi.spyOn(console, "info").mockImplementation(() => {});
+    const transport = new ConsoleTransport();
+    transport.write({ ts: "2025-01-01T00:00:00Z", level: "info", msg: "info msg", fields: { key: "val" } });
+    expect(spy).toHaveBeenCalledTimes(1);
+    expect(spy.mock.calls[0]?.[0]).toContain("info msg");
+    spy.mockRestore();
+  });
+
+  it("pipes warn records to console.warn", () => {
+    const spy = vi.spyOn(console, "warn").mockImplementation(() => {});
+    const transport = new ConsoleTransport();
+    transport.write({ ts: "2025-01-01T00:00:00Z", level: "warn", msg: "w", fields: {} });
+    expect(spy).toHaveBeenCalledTimes(1);
+    spy.mockRestore();
+  });
+
+  it("pipes error records to console.error", () => {
+    const spy = vi.spyOn(console, "error").mockImplementation(() => {});
+    const transport = new ConsoleTransport();
+    transport.write({ ts: "2025-01-01T00:00:00Z", level: "error", msg: "e", fields: {} });
+    expect(spy).toHaveBeenCalledTimes(1);
+    spy.mockRestore();
+  });
+
+  it("flush is a no-op that resolves immediately", async () => {
+    const transport = new ConsoleTransport();
+    await expect(transport.flush()).resolves.toBeUndefined();
+  });
+});

src/observability/logger/console-transport.ts

@@ -0,0 +1,36 @@
+import type { LogRecord, LogTransport } from "./types.js";
+
+/**
+ * Dev-mode transport that pipes log records to the browser/Node console.
+ * Each record is printed as `[LEVEL] ts msg {fields}`.
+ */
+export class ConsoleTransport implements LogTransport {
+  write(record: LogRecord): void {
+    const prefix = `[${record.level.toUpperCase()}] ${record.ts}`;
+    const hasFields = Object.keys(record.fields).length > 0;
+    const msg = hasFields
+      ? `${prefix} ${record.msg} ${JSON.stringify(record.fields)}`
+      : `${prefix} ${record.msg}`;
+
+    switch (record.level) {
+      case "debug":
+        // eslint-disable-next-line no-console
+        console.debug(msg);
+        break;
+      case "info":
+        // eslint-disable-next-line no-console
+        console.info(msg);
+        break;
+      case "warn":
+        console.warn(msg);
+        break;
+      case "error":
+        console.error(msg);
+        break;
+    }
+  }
+
+  async flush(): Promise<void> {
+    // Console output is synchronous — nothing to flush.
+  }
+}