Implement new path parser (#1378)

Regexps are quite leaky for complex parsing. Regression tests caught
a few issues related to path parser.

In this diff I implemented the new spec-compliant parser which solves
2 regression cases and covers many edge cases hard to handle with
regexps.

lib/path.test.js

@@ -0,0 +1,76 @@
+'use strict';
+
+const { expect } = require('chai');
+const { parsePathData } = require('./path.js');
+
+describe('parse path data', () => {
+  it('should allow spaces between commands', () => {
+    expect(parsePathData('M0 10 L \n\r\t20 30')).to.deep.equal([
+      { command: 'M', args: [0, 10] },
+      { command: 'L', args: [20, 30] },
+    ]);
+  });
+  it('should allow spaces and commas between arguments', () => {
+    expect(parsePathData('M0 , 10 L 20 \n\r\t30,40,50')).to.deep.equal([
+      { command: 'M', args: [0, 10] },
+      { command: 'L', args: [20, 30] },
+      { command: 'L', args: [40, 50] },
+    ]);
+  });
+  it('should forbid commas before commands', () => {
+    expect(parsePathData(', M0 10')).to.deep.equal([]);
+  });
+  it('should forbid commas between commands', () => {
+    expect(parsePathData('M0,10 , L 20,30')).to.deep.equal([
+      { command: 'M', args: [0, 10] },
+    ]);
+  });
+  it('should forbid commas between command name and argument', () => {
+    expect(parsePathData('M0,10 L,20,30')).to.deep.equal([
+      { command: 'M', args: [0, 10] },
+    ]);
+  });
+  it('should forbid multipe commas in a row', () => {
+    expect(parsePathData('M0 , , 10')).to.deep.equal([]);
+  });
+  it('should stop when unknown char appears', () => {
+    expect(parsePathData('M0 10 , L 20 #40')).to.deep.equal([
+      { command: 'M', args: [0, 10] },
+    ]);
+  });
+  it('should stop when not enough arguments', () => {
+    expect(parsePathData('M0 10 L 20 L 30 40')).to.deep.equal([
+      { command: 'M', args: [0, 10] },
+    ]);
+  });
+  it('should stop if moveto not the first command', () => {
+    expect(parsePathData('L 10 20')).to.deep.equal([]);
+    expect(parsePathData('10 20')).to.deep.equal([]);
+  });
+  it('should stop on invalid numbers', () => {
+    expect(parsePathData('M ...')).to.deep.equal([]);
+  });
+  it('should handle arcs', () => {
+    expect(
+      parsePathData(
+        `
+          M600,350
+          l 50,-25
+          a25,25 -30 0,1 50,-25
+          25,50 -30 0,1 50,-25
+          25,75 -30 0,1 50,-25
+          a25,100 -30 0,1 50,-25
+          l 50,-25
+        `
+      )
+    ).to.deep.equal([
+      { command: 'M', args: [600, 350] },
+      { command: 'l', args: [50, -25] },
+      { command: 'a', args: [25, 25, -30, 0, 1, 50, -25] },
+      { command: 'a', args: [25, 50, -30, 0, 1, 50, -25] },
+      { command: 'a', args: [25, 75, -30, 0, 1, 50, -25] },
+      { command: 'a', args: [25, 100, -30, 0, 1, 50, -25] },
+      { command: 'l', args: [50, -25] },
+    ]);
+  });
+});