Fixes #8. Combining marks and ZWJ's don't really exist.

lib/index.js

@@ -230,9 +230,7 @@ export function LB09(state) {
   // where X is any line break class except BK, CR, LF, NL, SP, or ZW.
   if (![BK, CR, LF, NL, SP, ZW].includes(state.cur.cls)
       && ((state.next.cls === CM) || (state.next.cls === ZWJ))) {
-    state.next.cls = state.cur.cls;
-    state.next.char = state.cur.char;
-    state.next.cp = state.cur.cp;
+    state.next.ignored = true;
     return NO_BREAK;
   }
   return PASS;

lib/state.js

@@ -71,6 +71,12 @@ export class BreakerChar {
    */
   len = 0;
 
+  /**
+   * If true, this is an LB9 CM or ZWJ that is treated as coalesced into
+   * the previous code point.
+   */
+  ignored = false;
+
   /**
    * @param {number} cls
    * @param {number} cp
@@ -93,7 +99,7 @@ export class BreakerChar {
    * @returns
    */
   [Symbol.for('nodejs.util.inspect.custom')](_depth, _inspectOptions, _inspect) {
-    return `${classText(this.cls)}(${this.cp.toString(16).padStart(4, '0')}:${JSON.stringify(this.char)})`;
+    return `${classText(this.cls)}(${this.cp.toString(16).padStart(4, '0')}:${JSON.stringify(this.char)})${this.ignored ? 'Ig' : ''}`;
   }
 }
 
@@ -145,8 +151,12 @@ export class BreakerState {
    * @param {BreakerChar} step
    */
   push(step) {
-    this.prev = this.cur;
-    this.cur = this.next;
+    if (this.next.ignored) {
+      this.cur.len = this.next.len;
+    } else {
+      this.prev = this.cur;
+      this.cur = this.next;
+    }
     this.next = step;
   }
 

test/index.test.js

@@ -20,11 +20,6 @@ describe('unicode line break tests', function() {
     if (!line || /^#/.test(line)) { return; }
 
     const [cols, comment] = line.split('#');
-
-    // In 15.1, row 10287 really doesn't seem right to me.
-    if (cols === '× 1B18 ÷ 1B27 × 1B44 × 200C × 1B2B × 1B38 ÷ 1B31 × 1B44 × 1B1D × 1B36 ÷\t') {
-      return;
-    }
     const codePoints = cols.split(/\s*[×÷]\s*/).slice(1, -1).map(c => parseInt(c, 16));
     const str = String.fromCodePoint(...codePoints);
 

test/state.test.js

@@ -18,6 +18,11 @@ describe('manage parsing state', () => {
     const str = '123';
     const state = new BreakerState(str);
     assert.deepEqual([...state.codePoints(1)].map(s => s.len), [2, 3]);
+    // Initialized with sot, sot, sot
+    const first = state.afterNext();
+    assert.deepEqual(first.char, '1');
+    state.push(first);
+    assert.deepEqual(state.afterNext().char, '2');
   });
 
   it('resolves Mn and Mc', () => {
@@ -36,6 +41,7 @@ describe('manage parsing state', () => {
     state.RI = 1;
     state.ex7pos = 5;
     state.setProp('foo', 'bar');
-    assert.equal(util.inspect(state), 'sot(-Infinity:"") => XX(-Infinity:"") => eot(-Infinity:"") LB8 spaces RI: 1 ex7: 5 {"foo":"bar"}');
+    state.next.ignored = true;
+    assert.equal(util.inspect(state), 'sot(-Infinity:"") => XX(-Infinity:"") => eot(-Infinity:"")Ig LB8 spaces RI: 1 ex7: 5 {"foo":"bar"}');
   });
 });