fix: fix foruma parsing with negative A, closes #28

Author: mdevils

src/parser.ts

@@ -413,51 +413,67 @@ export function createParser(
         return attr;
     }
 
-    function parseNumber(signed: boolean) {
+    function parseNumber() {
         let result = '';
-        if (signed && is('-')) {
-            result = readAndNext();
-        }
         while (digitsChars[chr]) {
             result += readAndNext();
         }
-        assert(result !== '' && result !== '-', 'Formula parse error.');
+        assert(result !== '', 'Formula parse error.');
         return parseInt(result);
     }
 
     const isNumberStart = () => is('-') || is('+') || digitsChars[chr];
 
     function parseFormula(): [number, number] {
+        if (is('e') || is('o')) {
+            const ident = parseIdentifier();
+            if (ident === 'even') {
+                skipWhitespace();
+                return [2, 0];
+            }
+            if (ident === 'odd') {
+                skipWhitespace();
+                return [2, 1];
+            }
+        }
+
         let firstNumber: null | number = null;
+        let firstNumberMultiplier = 1;
+        if (is('-')) {
+            next();
+            firstNumberMultiplier = -1;
+        }
         if (isNumberStart()) {
             if (is('+')) {
                 next();
-                assert(!is('-'), 'Formula parse error.');
             }
-            firstNumber = parseNumber(true);
+            firstNumber = parseNumber();
             if (!is('\\') && !is('n')) {
-                return [0, firstNumber];
+                return [0, firstNumber * firstNumberMultiplier];
             }
         }
         if (firstNumber === null) {
             firstNumber = 1;
         }
-        const ident = parseIdentifier();
-        if (ident === 'even') {
-            skipWhitespace();
-            return [2, 0];
-        }
-        if (ident === 'odd') {
-            skipWhitespace();
-            return [2, 1];
+        firstNumber *= firstNumberMultiplier;
+        let identifier;
+        if (is('\\')) {
+            next();
+            if (isHex(chr)) {
+                identifier = parseHex();
+            } else {
+                identifier = readAndNext();
+            }
+        } else {
+            identifier = readAndNext();
         }
-        assert(ident === 'n', 'Formula parse error');
+        assert(identifier === 'n', 'Formula parse error: expected "n".');
         skipWhitespace();
         if (is('+') || is('-')) {
             const sign = is('+') ? 1 : -1;
             next();
             skipWhitespace();
-            return [firstNumber, sign * parseNumber(false)];
+            return [firstNumber, sign * parseNumber()];
         } else {
             return [firstNumber, 0];
         }

src/render.ts

@@ -18,7 +18,7 @@ function renderSubstitution(sub: AstSubstitution) {
 
 function renderFormula(a: number, b: number) {
     if (a) {
-        let result = `${a === 1 ? '' : a}n`;
+        let result = `${a === 1 ? '' : a === -1 ? '-' : a}n`;
         if (b) {
             result += `${b > 0 ? '+' : ''}${b}`;
         }

test/parser.test.ts

@@ -921,6 +921,32 @@ describe('parse()', () => {
                 );
             }
         });
+        it('should properly parse with 0n and negative B', () => {
+            const sameFormulas = [
+                ':nth-child(0n-5)',
+                ':nth-child( 0n - 5 )',
+                ':nth-child( 0n-5 )',
+                ':nth-child(-5)',
+                ':nth-child( -5 )',
+                ':nth-child( -5 )'
+            ];
+            for (const formula of sameFormulas) {
+                expect(parse(formula)).toEqual(
+                    ast.selector({
+                        rules: [
+                            ast.rule({
+                                pseudoClasses: [
+                                    ast.pseudoClass({
+                                        name: 'nth-child',
+                                        argument: ast.formula({a: 0, b: -5})
+                                    })
+                                ]
+                            })
+                        ]
+                    })
+                );
+            }
+        });
         it('should properly parse with 0 B', () => {
             const sameFormulas = [
                 ':nth-child(3n+0)',

test/render.test.ts

@@ -43,6 +43,20 @@ const testCases = {
     'tag1:lang(en\\))': 'tag1:lang(en\\))',
     'tag1:nth-child(odd)': 'tag1:nth-child(2n+1)',
     'tag1:nth-child(even)': 'tag1:nth-child(2n)',
+    'tag1:nth-child( odd )': 'tag1:nth-child(2n+1)',
+    'tag1:nth-child( even )': 'tag1:nth-child(2n)',
+    'tag1:nth-child(-n+3)': 'tag1:nth-child(-n+3)',
+    'tag1:nth-child(-1n+3)': 'tag1:nth-child(-n+3)',
+    'tag1:nth-child(-5n+3)': 'tag1:nth-child(-5n+3)',
+    'tag1:nth-child(-5n-3)': 'tag1:nth-child(-5n-3)',
+    'tag1:nth-child(-5\\n-3)': 'tag1:nth-child(-5n-3)',
+    'tag1:nth-child(-5\\6e-3)': 'tag1:nth-child(-5n-3)',
+    'tag1:nth-child(-5n)': 'tag1:nth-child(-5n)',
+    'tag1:nth-child(5)': 'tag1:nth-child(5)',
+    'tag1:nth-child(-5)': 'tag1:nth-child(-5)',
+    'tag1:nth-child(0)': 'tag1:nth-child(0)',
+    'tag1:nth-child(n)': 'tag1:nth-child(n)',
+    'tag1:nth-child(-n)': 'tag1:nth-child(-n)',
     'tag1:has(.class)': 'tag1:has(.class)',
     'tag1:has(.class,.class2)': 'tag1:has(.class, .class2)',
     'tag1:has(.class:has(.subcls),.class2)': 'tag1:has(.class:has(.subcls), .class2)',