react to ENAMETOOLONG errors

packages/server/lib/screenshots.js

@@ -18,6 +18,14 @@ const pathSeparatorRe = /[\\\/]/g
 // internal id incrementor
 let __ID__ = null
 
+// many filesystems limit filename length to 255 bytes/characters, so truncate the filename to
+// the smallest common denominator of safe filenames, which is 255 bytes. when ENAMETOOLONG
+// errors are encountered, `maxSafeBytes` will be decremented to at most `MIN_PREFIX_BYTES`, at
+// which point the latest ENAMTOOLONG error will be emitted.
+// @see https://en.wikipedia.org/wiki/Comparison_of_file_systems#Limits
+let maxSafeBytes = 255
+const MIN_PREFIX_BYTES = 64
+
 // TODO: when we parallelize these builds we'll need
 // a semaphore to access the file system when we write
 // screenshots since its possible two screenshots with
@@ -288,17 +296,13 @@ const getDimensions = function (details) {
   return pick(details.image.bitmap)
 }
 
-const ensureUniquePath = function (withoutExt, extension, num = 0) {
+const ensureSafePath = function (withoutExt, extension, num = 0) {
   const suffix = `${num ? ` (${num})` : ''}.${extension}`
-  // many filesystems limit filename length to 255 bytes/characters, so truncate the filename to
-  // the smallest common denominator of safe filenames, which is 255 bytes
-  // @see https://github.com/cypress-io/cypress/issues/2403
-  // @see https://en.wikipedia.org/wiki/Comparison_of_file_systems#Limits
-  const maxSafeBytes = 255 - suffix.length
+  const maxSafePrefixBytes = maxSafeBytes - suffix.length
   const filenameBuf = Buffer.from(path.basename(withoutExt))
 
-  if (filenameBuf.byteLength > maxSafeBytes) {
-    const truncated = filenameBuf.slice(0, maxSafeBytes).toString()
+  if (filenameBuf.byteLength > maxSafePrefixBytes) {
+    const truncated = filenameBuf.slice(0, maxSafePrefixBytes).toString()
 
     withoutExt = path.join(path.dirname(withoutExt), truncated)
   }
@@ -308,10 +312,21 @@ const ensureUniquePath = function (withoutExt, extension, num = 0) {
   return fs.pathExists(fullPath)
   .then((found) => {
     if (found) {
-      return ensureUniquePath(withoutExt, extension, num + 1)
+      return ensureSafePath(withoutExt, extension, num + 1)
     }
 
-    return fullPath
+    // path does not exist, attempt to create it to check for an ENAMETOOLONG error
+    return fs.outputFileAsync(fullPath, '')
+    .then(() => fullPath)
+    .catch((err) => {
+      if (err.code === 'ENAMETOOLONG' && maxSafePrefixBytes >= MIN_PREFIX_BYTES) {
+        maxSafeBytes -= 1
+
+        return ensureSafePath(withoutExt, extension, num)
+      }
+
+      throw err
+    })
   })
 }
 
@@ -346,7 +361,7 @@ const getPath = function (data, ext, screenshotsFolder) {
 
   const withoutExt = path.join(screenshotsFolder, ...specNames, ...names)
 
-  return ensureUniquePath(withoutExt, ext)
+  return ensureSafePath(withoutExt, ext)
 }
 
 const getPathToScreenshot = function (data, details, screenshotsFolder) {