wrangler tail tty-awareness and json-respecting (#810)

2 quick fixes:

- Check `process.stdout.isTTY` at runtime to determine whether to default to "pretty" or "json" output for tailing.
- Only print messages like "Connected to {worker}" if in "pretty" mode (errors still throw strings)

.changeset/unlucky-terms-film.md

@@ -0,0 +1,12 @@
+---
+"wrangler": patch
+---
+
+Make `wrangler tail` TTY-aware, and stop printing non-JSON in JSON mode
+
+Closes #493
+
+2 quick fixes:
+
+- Check `process.stdout.isTTY` at runtime to determine whether to default to "pretty" or "json" output for tailing.
+- Only print messages like "Connected to {worker}" if in "pretty" mode (errors still throw strings)

packages/wrangler/src/__tests__/helpers/mock-istty.ts

@@ -0,0 +1,23 @@
+const ORIGINAL_ISTTY = process.stdout.isTTY;
+
+/**
+ * Mock `process.stdout.isTTY`
+ */
+export function useMockIsTTY() {
+  /**
+   * Explicitly set `process.stdout.isTTY` to a given value
+   */
+  const setIsTTY = (isTTY: boolean) => {
+    process.stdout.isTTY = isTTY;
+  };
+
+  beforeEach(() => {
+    process.stdout.isTTY = ORIGINAL_ISTTY;
+  });
+
+  afterEach(() => {
+    process.stdout.isTTY = ORIGINAL_ISTTY;
+  });
+
+  return { setIsTTY };
+}

packages/wrangler/src/__tests__/tail.test.ts

@@ -3,6 +3,7 @@ import { Headers, Request } from "undici";
 import { mockAccountId, mockApiToken } from "./helpers/mock-account-id";
 import { setMockResponse, unsetAllMocks } from "./helpers/mock-cfetch";
 import { mockConsoleMethods } from "./helpers/mock-console";
+import { useMockIsTTY } from "./helpers/mock-istty";
 import { runInTempDir } from "./helpers/run-in-tmp";
 import { runWrangler } from "./helpers/run-wrangler";
 import type { TailEventMessage, RequestEvent, ScheduledEvent } from "../tail";
@@ -216,6 +217,8 @@ describe("tail", () => {
   });
 
   describe("printing", () => {
+    const { setIsTTY } = useMockIsTTY();
+
     it("logs request messages in JSON format", async () => {
       const api = mockWebsocketAPIs();
       await runWrangler("tail test-worker --format json");
@@ -266,8 +269,34 @@ describe("tail", () => {
       `);
     });
 
-    it("defaults to logging in pretty format", async () => {
-      // the same test as the one before, but without the --format flag
+    it("logs scheduled messages in pretty format", async () => {
+      const api = mockWebsocketAPIs();
+      await runWrangler("tail test-worker --format pretty");
+
+      const event = generateMockScheduledEvent();
+      const message = generateMockEventMessage({ event });
+      const serializedMessage = serialize(message);
+
+      api.ws.send(serializedMessage);
+      expect(
+        std.out
+          .replace(
+            new Date(mockEventTimestamp).toLocaleString(),
+            "[mock timestamp string]"
+          )
+          .replace(
+            mockTailExpiration.toLocaleString(),
+            "[mock expiration date]"
+          )
+      ).toMatchInlineSnapshot(`
+        "successfully created tail, expires at [mock expiration date]
+        Connected to test-worker, waiting for logs...
+        \\"* * * * *\\" @ [mock timestamp string] - Ok"
+      `);
+    });
+
+    it("defaults to logging in pretty format when the output is a TTY", async () => {
+      setIsTTY(true);
       const api = mockWebsocketAPIs();
       await runWrangler("tail test-worker");
 
@@ -293,7 +322,22 @@ describe("tail", () => {
       `);
     });
 
+    it("defaults to logging in json format when the output is not a TTY", async () => {
+      setIsTTY(false);
+
+      const api = mockWebsocketAPIs();
+      await runWrangler("tail test-worker");
+
+      const event = generateMockRequestEvent();
+      const message = generateMockEventMessage({ event });
+      const serializedMessage = serialize(message);
+
+      api.ws.send(serializedMessage);
+      expect(std.out).toMatch(deserializeToJson(serializedMessage));
+    });
+
     it("logs console messages and exceptions", async () => {
+      setIsTTY(true);
       const api = mockWebsocketAPIs();
       await runWrangler("tail test-worker");
 
@@ -341,32 +385,6 @@ describe("tail", () => {
       `);
       expect(std.warn).toMatchInlineSnapshot(`""`);
     });
-
-    it("logs scheduled messages in pretty format", async () => {
-      const api = mockWebsocketAPIs();
-      await runWrangler("tail test-worker --format pretty");
-
-      const event = generateMockScheduledEvent();
-      const message = generateMockEventMessage({ event });
-      const serializedMessage = serialize(message);
-
-      api.ws.send(serializedMessage);
-      expect(
-        std.out
-          .replace(
-            new Date(mockEventTimestamp).toLocaleString(),
-            "[mock timestamp string]"
-          )
-          .replace(
-            mockTailExpiration.toLocaleString(),
-            "[mock expiration date]"
-          )
-      ).toMatchInlineSnapshot(`
-        "successfully created tail, expires at [mock expiration date]
-        Connected to test-worker, waiting for logs...
-        \\"* * * * *\\" @ [mock timestamp string] - Ok"
-      `);
-    });
   });
 });
 

packages/wrangler/src/index.tsx

@@ -1071,59 +1071,56 @@ export async function main(argv: string[]): Promise<void> {
     "tail [name]",
     "🦚 Starts a log tailing session for a published Worker.",
     (yargs) => {
-      return (
-        yargs
-          .positional("name", {
-            describe: "Name of the worker",
-            type: "string",
-          })
-          // TODO: auto-detect if this should be json or pretty based on atty
-          .option("format", {
-            default: "pretty",
-            choices: ["json", "pretty"],
-            describe: "The format of log entries",
-          })
-          .option("status", {
-            choices: ["ok", "error", "canceled"],
-            describe: "Filter by invocation status",
-            array: true,
-          })
-          .option("header", {
-            type: "string",
-            describe: "Filter by HTTP header",
-          })
-          .option("method", {
-            type: "string",
-            describe: "Filter by HTTP method",
-            array: true,
-          })
-          .option("sampling-rate", {
-            type: "number",
-            describe: "Adds a percentage of requests to log sampling rate",
-          })
-          .option("search", {
-            type: "string",
-            describe: "Filter by a text match in console.log messages",
-          })
-          .option("ip", {
-            type: "string",
-            describe:
-              'Filter by the IP address the request originates from. Use "self" to filter for your own IP',
-            array: true,
-          })
-          .option("env", {
-            type: "string",
-            describe: "Perform on a specific environment",
-            alias: "e",
-          })
-          .option("debug", {
-            type: "boolean",
-            hidden: true,
-            default: false,
-            describe:
-              "If a log would have been filtered out, send it through anyway alongside the filter which would have blocked it.",
-          })
-      );
+      return yargs
+        .positional("name", {
+          describe: "Name of the worker",
+          type: "string",
+        })
+        .option("format", {
+          default: process.stdout.isTTY ? "pretty" : "json",
+          choices: ["json", "pretty"],
+          describe: "The format of log entries",
+        })
+        .option("status", {
+          choices: ["ok", "error", "canceled"],
+          describe: "Filter by invocation status",
+          array: true,
+        })
+        .option("header", {
+          type: "string",
+          describe: "Filter by HTTP header",
+        })
+        .option("method", {
+          type: "string",
+          describe: "Filter by HTTP method",
+          array: true,
+        })
+        .option("sampling-rate", {
+          type: "number",
+          describe: "Adds a percentage of requests to log sampling rate",
+        })
+        .option("search", {
+          type: "string",
+          describe: "Filter by a text match in console.log messages",
+        })
+        .option("ip", {
+          type: "string",
+          describe:
+            'Filter by the IP address the request originates from. Use "self" to filter for your own IP',
+          array: true,
+        })
+        .option("env", {
+          type: "string",
+          describe: "Perform on a specific environment",
+          alias: "e",
+        })
+        .option("debug", {
+          type: "boolean",
+          hidden: true,
+          default: false,
+          describe:
+            "If a log would have been filtered out, send it through anyway alongside the filter which would have blocked it.",
+        });
     },
     async (args) => {
       if (args.format === "pretty") {
@@ -1164,9 +1161,11 @@ export async function main(argv: string[]): Promise<void> {
         args.env && !isLegacyEnv(config) ? ` (${args.env})` : ""
       }`;
 
-      console.log(
-        `successfully created tail, expires at ${expiration.toLocaleString()}`
-      );
+      if (args.format === "pretty") {
+        console.log(
+          `successfully created tail, expires at ${expiration.toLocaleString()}`
+        );
+      }
 
       onExit(async () => {
         tail.terminate();
@@ -1193,7 +1192,9 @@ export async function main(argv: string[]): Promise<void> {
         }
       }
 
-      console.log(`Connected to ${scriptDisplayName}, waiting for logs...`);
+      if (args.format === "pretty") {
+        console.log(`Connected to ${scriptDisplayName}, waiting for logs...`);
+      }
 
       tail.on("close", async () => {
         tail.terminate();