Logger: ignore empty lines in JSON Mode

.changeset/eight-parents-add.md

@@ -0,0 +1,5 @@
+---
+'@openfn/logger': patch
+---
+
+In JSON mode, don't log empty messages

.changeset/old-swans-clean.md

@@ -0,0 +1,5 @@
+---
+'@openfn/ws-worker': patch
+---
+
+Ignore empty log lines (don't send them to lightning)

integration-tests/worker/test/integration.test.ts

@@ -561,6 +561,31 @@ test.serial("Don't send job logs to stdout", (t) => {
   });
 });
 
+// This is a test against job logs - but it should work
+// exactly the same way for all logs
+test.serial("Don't send empty logs to lightning", (t) => {
+  return new Promise(async (done) => {
+    const attempt = {
+      id: crypto.randomUUID(),
+      jobs: [
+        {
+          adaptor: '@openfn/language-common@latest',
+          body: 'fn((s) =>  { console.log(); return s })',
+        },
+      ],
+    };
+
+    lightning.once('run:complete', () => {
+      // The engine logger shouldn't print out any job logs
+      const jobLogs = engineLogger._history.filter((l) => l.name === 'JOB');
+      t.is(jobLogs.length, 0);
+      done();
+    });
+
+    lightning.enqueueRun(attempt);
+  });
+});
+
 test.serial('Include timestamps on basically everything', (t) => {
   return new Promise(async (done) => {
     const attempt = {

packages/logger/src/logger.ts

@@ -158,6 +158,14 @@ export default function (name?: string, options: LogOptions = {}): Logger {
     level: LogFns,
     ...args: LogArgs
   ) => {
+    if (args.length === 0) {
+      // In JSON mode, don't log empty lines
+      // (mostly because this spams Lightning with nonsense, but more generally
+      // if you have machine readable logs then "whitespace" or "formatting" logs,
+      // like console.break(), are meaningless)
+      return;
+    }
+
     const message = args.map((o) =>
       sanitize(o, {
         stringify: false,

packages/logger/test/logger.test.ts

@@ -354,6 +354,17 @@ test('json mode should serialize errors nicely', (t) => {
   t.deepEqual(result.message[0], { name: 'Error', message: 'wibble' });
 });
 
+test('json mode should not log empty lines', (t) => {
+  const logger = createLogger<JSONLog>(undefined, {
+    level: 'info',
+    json: true,
+  });
+
+  logger.info();
+
+  t.is(logger._history.length, 0);
+});
+
 test('with level=default, logs success, error and warning but not info and debug', (t) => {
   const logger = createLogger<StringLog>('x', { level: 'default' });