chore: Simplify processAspectRatio to not use a custom RegExp

Author: gabrieldonadel

Libraries/StyleSheet/__tests__/__snapshots__/processAspectRatio-test.js.snap

@@ -1,9 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
-exports[`processAspectRatio should not accept invalid formats 1`] = `"aspectRatio must either be a number or a ratio. You passed: -1"`;
+exports[`processAspectRatio should not accept invalid formats 1`] = `"aspectRatio must either be a number, a ratio or \`auto\`. You passed: 0a"`;
 
-exports[`processAspectRatio should not accept invalid formats 2`] = `"aspectRatio must either be a number or a ratio. You passed: 0a"`;
+exports[`processAspectRatio should not accept invalid formats 2`] = `"aspectRatio must either be a number, a ratio or \`auto\`. You passed: 1 / 1 1"`;
 
-exports[`processAspectRatio should not accept invalid formats 3`] = `"aspectRatio must either be a number or a ratio. You passed: / 0"`;
-
-exports[`processAspectRatio should not accept invalid formats 4`] = `"aspectRatio must either be a number or a ratio. You passed: 1 / 1 1"`;
+exports[`processAspectRatio should not accept invalid formats 3`] = `"aspectRatio must either be a number, a ratio or \`auto\`. You passed: auto 1/1"`;

Libraries/StyleSheet/__tests__/processAspectRatio-test.js

@@ -28,6 +28,12 @@ describe('processAspectRatio', () => {
     expect(processAspectRatio('   0    ')).toBe(0);
   });
 
+  it('should accept `auto`', () => {
+    expect(processAspectRatio('auto')).toBe(undefined);
+    expect(processAspectRatio(' auto')).toBe(undefined);
+    expect(processAspectRatio(' auto  ')).toBe(undefined);
+  });
+
   it('should accept ratios', () => {
     expect(processAspectRatio('+1/1')).toBe(1);
     expect(processAspectRatio('0 / 10')).toBe(0);
@@ -37,9 +43,8 @@ describe('processAspectRatio', () => {
   });
 
   it('should not accept invalid formats', () => {
-    expect(() => processAspectRatio('-1')).toThrowErrorMatchingSnapshot();
     expect(() => processAspectRatio('0a')).toThrowErrorMatchingSnapshot();
-    expect(() => processAspectRatio('/ 0')).toThrowErrorMatchingSnapshot();
     expect(() => processAspectRatio('1 / 1 1')).toThrowErrorMatchingSnapshot();
+    expect(() => processAspectRatio('auto 1/1')).toThrowErrorMatchingSnapshot();
   });
 });

Libraries/StyleSheet/processAspectRatio.js

@@ -17,27 +17,37 @@ function processAspectRatio(aspectRatio: number | string): ?number {
     return aspectRatio;
   }
 
-  const match = new RegExp(
-    /(^\s*[+]?\d+([.]\d+)?\s*$)|(^\s*([+]?\d+([.]\d+)?)\s*\/\s*([+]?\d+([.]\d+)?)\s*$)/,
-  ).exec(aspectRatio);
+  const matches = aspectRatio.split('/').map(s => s.trim());
+
+  if (matches.includes('auto')) {
+    if (__DEV__) {
+      invariant(
+        matches.length,
+        'aspectRatio does not support `auto <ratio>`. You passed: %s',
+        aspectRatio,
+      );
+    }
+    return;
+  }
 
+  const hasNonNumericValues = matches.some(n => Number.isNaN(Number(n)));
   if (__DEV__) {
     invariant(
-      Boolean(match),
-      'aspectRatio must either be a number or a ratio. You passed: %s',
+      !hasNonNumericValues && (matches.length === 1 || matches.length === 2),
+      'aspectRatio must either be a number, a ratio or `auto`. You passed: %s',
       aspectRatio,
     );
   }
 
-  if (!match) {
+  if (hasNonNumericValues) {
     return;
   }
 
-  if (match[4] !== undefined) {
-    return Number(match[4]) / Number(match[6]);
+  if (matches.length === 2) {
+    return Number(matches[0]) / Number(matches[1]);
   }
 
-  return Number(match[1]);
+  return Number(matches[0]);
 }
 
 module.exports = processAspectRatio;