fix: preserve npm run output without trailing newline

Author: cp89-cyber

lib/utils/display.js

@@ -427,6 +427,7 @@ class Progress {
   #lastUpdate = 0
   #interval
   #timeout
+  #rendered = false
 
   // We are rendering is enabled option is set and we are not waiting for the render timeout
   get #rendering () {
@@ -511,12 +512,17 @@ class Progress {
     }
     this.#clearSpinner()
     this.#stream.write(this.#spinner.frames[this.#frameIndex])
+    this.#rendered = true
   }
 
   #clearSpinner () {
+    if (!this.#rendered) {
+      return
+    }
     // Move to the start of the line and clear the rest of the line
     this.#stream.cursorTo(0)
     this.#stream.clearLine(1)
+    this.#rendered = false
   }
 }
 

test/lib/utils/display.js

@@ -29,6 +29,7 @@ const mockDisplay = async (t, { mocks, load } = {}) => {
     ...procLog,
     display,
     displayLoad,
+    streams: logs.streams,
     ...logs.logs,
   }
 }
@@ -101,6 +102,50 @@ t.test('can do progress', async (t) => {
   t.strictSame(outputs, ['before input', 'during input', 'after input'])
 })
 
+t.test('progress resume does not clear output when spinner inactive', async (t) => {
+  const { input, output, outputs, streams } = await mockDisplay(t, {
+    load: {
+      progress: true,
+    },
+  })
+
+  const origClearLine = streams.stderr.clearLine
+  const origCursorTo = streams.stderr.cursorTo
+  let clearCalls = 0
+  let cursorCalls = 0
+  streams.stderr.clearLine = (...args) => {
+    clearCalls++
+    return origClearLine.call(streams.stderr, ...args)
+  }
+  streams.stderr.cursorTo = (...args) => {
+    cursorCalls++
+    return origCursorTo.call(streams.stderr, ...args)
+  }
+
+  t.teardown(() => {
+    streams.stderr.clearLine = origClearLine
+    streams.stderr.cursorTo = origCursorTo
+  })
+
+  // ensure the spinner has rendered at least once so progress.off clears it
+  await timers.setTimeout(300)
+
+  const endInput = input.start()
+  await timers.setTimeout(0)
+
+  clearCalls = 0
+  cursorCalls = 0
+
+  output.standard('no trailing newline')
+
+  endInput()
+  await timers.setTimeout(0)
+
+  t.equal(clearCalls, 0, 'resume does not clear the line when spinner inactive')
+  t.equal(cursorCalls, 0, 'resume does not reposition cursor when spinner inactive')
+  t.equal(outputs.at(-1), 'no trailing newline', 'output remains visible')
+})
+
 t.test('handles log throwing', async (t) => {
   class ThrowInspect {
     #crashes = 0;