fix: shrink whitespace lines

Author: charleslien

npm-app/src/__tests__/display.test.ts

@@ -0,0 +1,226 @@
+// @ts-ignore: bun:test types aren't available
+import { describe, expect, it } from 'bun:test'
+import { gray } from 'picocolors'
+import { onlyWhitespace, squashNewlines } from '../display'
+
+const PREFIX = '.\r\n'
+
+// Helper function to simulate getLastTwoLines behavior
+function getLastTwoLines(str: string): string {
+  return PREFIX + str.split('\r\n').slice(-2).join('\r\n')
+}
+
+describe('squashNewlines', () => {
+  describe('when called with getLastTwoLines(previous) + chunk', () => {
+    it('should handle simple strings', () => {
+      const previous = 'line1\r\nline2\r\nline3'
+      const chunk = '\r\nline4\r\nline5'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + chunk)
+    })
+
+    it('should handle when chunk has empty lines', () => {
+      const previous = 'content\r\nmore content'
+      const chunk = '\r\n\r\n\r\nfinal line'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + '\r\n\r\nfinal line')
+    })
+
+    it('should handle when chunk has whitespace lines', () => {
+      const previous = 'first\r\nsecond\r\nthird'
+      const chunk = '\r\n   \r\n\t\r\nfourth'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + '\r\n   \r\n\tfourth')
+    })
+
+    it('should handle when previous is empty', () => {
+      const previous = ''
+      const chunk = 'some\r\ncontent'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + chunk)
+    })
+
+    it('should handle when chunk is empty', () => {
+      const previous = 'some\r\ncontent\r\nhere'
+      const chunk = ''
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + chunk)
+    })
+
+    it('should handle when both strings are empty', () => {
+      const previous = ''
+      const chunk = ''
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + chunk)
+    })
+
+    it('should handle complex mixed content', () => {
+      const previous = 'alpha\r\nbeta\r\ngamma\r\ndelta'
+      const chunk = '\r\n\r\n   \r\n\t\r\n\r\nepsilon\r\nzeta'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + '\r\n\r\n   \tepsilon\r\nzeta')
+    })
+
+    it('should handle when previous has only newlines', () => {
+      const previous = '\r\n\r\n\r\n'
+      const chunk = 'content'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + chunk)
+    })
+
+    it('should handle when chunk has only newlines', () => {
+      const previous = 'content\r\nmore'
+      const chunk = '\r\n\r\n\r\n'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + '\r\n\r\n')
+    })
+
+    it('should handle single line inputs', () => {
+      const previous = 'single line'
+      const chunk = 'another line'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + chunk)
+    })
+
+    it('should handle previous ends with whitespace lines', () => {
+      const previous = 'content\r\n  \r\n\t'
+      const chunk = '\r\nmore content'
+      const lastTwoLines = getLastTwoLines(previous)
+      const combined = lastTwoLines + chunk
+      const squashed = squashNewlines(combined)
+
+      expect(squashed).toEqual(lastTwoLines + 'more content')
+    })
+  })
+
+  describe('squashNewlines behavior verification', () => {
+    it('should squash consecutive empty lines correctly', () => {
+      const input = PREFIX + 'line1\r\n\r\n\r\n\r\nline5'
+      const result = squashNewlines(input)
+
+      // Should reduce multiple consecutive empty lines to at most 2
+      expect(result).toBe(PREFIX + 'line1\r\n\r\nline5')
+    })
+
+    it('should preserve single empty lines', () => {
+      const input = PREFIX + 'line1\r\n\r\nline3'
+      const result = squashNewlines(input)
+
+      expect(result).toBe(input) // Should remain unchanged
+    })
+  })
+
+  describe('error handling', () => {
+    it('should throw error when input does not start with PREFIX', () => {
+      const invalidInput = 'invalid input without prefix'
+
+      expect(() => squashNewlines(invalidInput)).toThrow(
+        `Expected string to start with ${JSON.stringify(PREFIX)}`
+      )
+    })
+  })
+})
+
+describe('onlyWhitespace', () => {
+  it('should return true for empty string', () => {
+    expect(onlyWhitespace('')).toBe(true)
+  })
+
+  it('should return true for single space', () => {
+    expect(onlyWhitespace(' ')).toBe(true)
+  })
+
+  it('should return true for multiple spaces', () => {
+    expect(onlyWhitespace('   ')).toBe(true)
+  })
+
+  it('should return true for tab', () => {
+    expect(onlyWhitespace('\t')).toBe(true)
+  })
+
+  it('should return true for newline', () => {
+    expect(onlyWhitespace('\n')).toBe(true)
+  })
+
+  it('should return true for carriage return', () => {
+    expect(onlyWhitespace('\r')).toBe(true)
+  })
+
+  it('should return true for ANSI escape sequences', () => {
+    expect(onlyWhitespace('\u001b[31m')).toBe(true) // Red color
+    expect(onlyWhitespace('\u001b[0m')).toBe(true) // Reset
+  })
+
+  it('should return true for OSC sequences', () => {
+    const oscSequence =
+      '\u001b]697;OSCUnlock=683fe5e7c2d2476bb61d4e0588c15eec\u0007\u001b]697;Dir=/Users/jahooma/codebuff\u0007'
+    expect(onlyWhitespace(oscSequence)).toBe(true)
+  })
+
+  it('should return false for control characters', () => {
+    expect(onlyWhitespace('\u0000\u0001\u0002')).toBe(true) // Null, SOH, STX
+    expect(onlyWhitespace('\u007F')).toBe(true) // DEL
+  })
+
+  it('should return true for zero-width characters', () => {
+    expect(onlyWhitespace('\u200B')).toBe(true)
+    expect(onlyWhitespace('\u200C')).toBe(true)
+    expect(onlyWhitespace('\u200D')).toBe(true)
+  })
+
+  it('should return true for colored empty strings', () => {
+    expect(onlyWhitespace(gray(' '))).toBe(true)
+  })
+
+  it('should return false for visible text', () => {
+    expect(onlyWhitespace('hello')).toBe(false)
+    expect(onlyWhitespace('a')).toBe(false)
+    expect(onlyWhitespace('123')).toBe(false)
+  })
+
+  describe('real world examples', () => {
+    it('should return false for end of terminal command', () => {
+      expect(
+        onlyWhitespace(
+          '\u001b]697;OSCUnlock=683fe5e7c2d2476bb61d4e0588c15eec\u0007\u001b]697;Dir=/Users/jahooma/codebuff\u0007\u001b]697;Shell=bash\u0007\u001b]697;ShellPath=/bin/bash\u0007\u001b]697;PID=71631\u0007\u001b]697;ExitCode=0\u0007\u001b]697;TTY=/dev/ttys036\u0007\u001b]697;Log=\u0007\u001b]697;User=jahooma\u0007\u001b]697;OSCLock=683fe5e7c2d2476bb61d4e0588c15eec\u0007\u001b]697;PreExec\u0007\u001b]697;StartPrompt\u0007'
+        )
+      ).toBe(true)
+
+      expect(
+        onlyWhitespace(
+          '\u001b]0;charles@charles-framework-13:~/github/codebuff\u001b\\\u001b]7;file://charles-framework-13/home/charles/github/codebuff\u001b\\\u001b[?2004h'
+        )
+      ).toBe(true)
+    })
+  })
+})

npm-app/src/display.ts

@@ -5,9 +5,11 @@
  * renders as four newline characters. Because there is an ANSI escape
  * character between the first two and the last two newline characters.
  */
+import stringWidth from 'string-width'
 
+const PREFIX = '.\r\n'
 let squashingEnabled = false
-let previous = ' '
+let previous = PREFIX
 
 export function getPrevious(): string {
   return previous
@@ -25,14 +27,68 @@ export function disableSquashNewlines(): void {
   squashingEnabled = false
 }
 
+/** OSC  …  BEL | ST   (titles, hyperlinks, cwd hints, etc.) */
+const OSC = /\u001B\][^\u0007\u001B]*(?:\u0007|\u001B\\)/g
+
+/** CSI  …  final-byte   (cursor moves, ?2004h, colours if stripAnsi missed them) */
+const CSI = /\u001B\[[0-?]*[ -/]*[@-~]/g
+
+/** Zero-width Unicode code-points (format, combining, enclosing) */
+const ZW = /[\p{Cf}\p{Mn}\p{Me}]/gu
+
+/**
+ * `true` → after stripping VT controls and whitespace the string has zero width
+ */
+export function onlyWhitespace(raw: string): boolean {
+  const visible = raw
+    .replace(OSC, '') // remove OSC 0/7/8/133/697/…
+    .replace(CSI, '') // remove CSI H, A, ?2004h, …
+    .replace(/\s+/g, '') // remove spaces, tabs, CR, LF
+    .replace(ZW, '') // remove ZWJ, ZWNJ, VS16, etc.
+
+  return stringWidth(visible) === 0
+}
+
 function addCarriageReturn(str: string): string {
   // Do not copy over \n from previous
-  const base = (previous[previous.length - 1] === '\r' ? '\r' : ' ') + str
+  const base = (previous[previous.length - 1] === '\r' ? '\r' : '.') + str
   // Replace twice, because of no overlap '\n\n'
   const withCarriageReturns = base.replace(/(?<!\r)\n/g, '\r\n')
   return withCarriageReturns.slice(1)
 }
 
+function getLastTwoLines(str: string): string {
+  return PREFIX + str.split('\r\n').slice(-2).join('\r\n')
+}
+
+export function squashNewlines(str: string): string {
+  if (!str.startsWith(PREFIX)) {
+    throw new Error(`Expected string to start with ${JSON.stringify(PREFIX)}`)
+  }
+
+  const lines = str
+    .split('\r\n')
+    .map((line) => ({ line, empty: onlyWhitespace(line) }))
+
+  const agg: string[] = []
+  let consecutiveEmptyLines = 0
+  for (const { line, empty } of lines) {
+    if (consecutiveEmptyLines > 1) {
+      agg[agg.length - 1] += line
+    } else {
+      agg.push(line)
+    }
+
+    if (empty) {
+      consecutiveEmptyLines++
+    } else {
+      consecutiveEmptyLines = 0
+    }
+  }
+
+  return agg.join('\r\n')
+}
+
 const originalWrite = process.stdout.write.bind(process.stdout)
 
 process.stdout.write = function (
@@ -47,7 +103,7 @@ process.stdout.write = function (
 
   if (!squashingEnabled) {
     previous += chunkString
-    previous = previous.slice(previous.length - 4)
+    previous = getLastTwoLines(previous)
 
     if (typeof encodingOrCallback === 'function') {
       // Called like write(chunk, callback)
@@ -58,9 +114,9 @@ process.stdout.write = function (
   }
 
   const combinedContent = previous + chunkString
-  const processedContent = combinedContent.replace(/(\r\n){3,}/g, '\r\n\r\n')
+  const processedContent = squashNewlines(combinedContent)
   const processedChunk = processedContent.slice(previous.length)
-  previous = processedContent.slice(processedContent.length - 4)
+  previous = getLastTwoLines(processedContent)
 
   if (typeof encodingOrCallback === 'function') {
     // Called like write(chunk, callback)
@@ -84,7 +140,7 @@ process.stderr.write = function (
 
   if (!squashingEnabled) {
     previous += chunkString
-    previous = previous.slice(previous.length - 4)
+    previous = getLastTwoLines(previous)
 
     if (typeof encodingOrCallback === 'function') {
       // Called like write(chunk, callback)
@@ -95,9 +151,9 @@ process.stderr.write = function (
   }
 
   const combinedContent = previous + chunkString
-  const processedContent = combinedContent.replace(/\r\n{3,}/g, '\r\n\r\n')
+  const processedContent = squashNewlines(combinedContent)
   const processedChunk = processedContent.slice(previous.length)
-  previous = processedContent.slice(processedContent.length - 4)
+  previous = getLastTwoLines(processedContent)
 
   if (typeof encodingOrCallback === 'function') {
     // Called like write(chunk, callback)