src: replace byline with custom splitter

The byline package is generating deprecation warnings when running
strong-log-transformer under node 10. Since the package appears to be
unmaintained, we are re-implementing the functionality here.

The implementation is heavily inspired by byline, split, and split2, but
simplified for our specific use case.

The existing tests fully cover this new implementation, including the
corner case of the input stream being truncated in the middle of a
multi-byte UTF8 sequence.

Resolves #7.

Signed-off-by: Ryan Graham <r.m.graham@gmail.com>

Author: rmg

lib/logger.js

@@ -9,9 +9,9 @@ var stream = require('stream');
 var util = require('util');
 var fs = require('fs');
 
-var byline = require('byline');
 var through = require('through');
 var duplexer = require('duplexer');
+var StringDecoder = require('string_decoder').StringDecoder;
 
 module.exports = Logger;
 
@@ -30,7 +30,7 @@ var formatters = {
 function Logger(options) {
   var defaults = JSON.parse(JSON.stringify(Logger.DEFAULTS));
   options = util._extend(defaults, options || {});
-  var catcher = new byline.LineStream;
+  var catcher = deLiner();
   var emitter = catcher;
   var transforms = [
     objectifier(),
@@ -56,7 +56,7 @@ function Logger(options) {
 
   transforms.push(formatters[options.format](options));
 
-  // restore line endings that were removed by byline
+  // restore line endings that were removed by line splitting
   transforms.push(reLiner());
 
   for (var t in transforms) {
@@ -66,6 +66,34 @@ function Logger(options) {
   return duplexer(catcher, emitter);
 }
 
+function deLiner() {
+  var decoder = new StringDecoder('utf8');
+  var last = '';
+
+  return new stream.Transform({
+    transform(chunk, _enc, callback) {
+      last += decoder.write(chunk);
+      var list = last.split(/\r\n|[\n\v\f\r\x85\u2028\u2029]/g);
+      last = list.pop();
+      for (var i = 0; i < list.length; i++) {
+        // swallow empty lines
+        if (list[i]) {
+          this.push(list[i]);
+        }
+      }
+      callback();
+    },
+    flush(callback) {
+      // incomplete UTF8 sequences become UTF8 replacement characters
+      last += decoder.end();
+      if (last) {
+        this.push(last);
+      }
+      callback();
+    },
+  });
+}
+
 function reLiner() {
   return through(appendNewline);
 

package.json

@@ -27,7 +27,6 @@
     "test": "tap --100 test/test-*"
   },
   "dependencies": {
-    "byline": "^5.0.0",
     "duplexer": "^0.1.1",
     "minimist": "^1.2.0",
     "through": "^2.3.4"