feat: support arbitrary opacity values

docs/src/content/docs/reference/layout.md

@@ -89,6 +89,18 @@ Control layout with flexbox, positioning, and display utilities.
 <View className="overflow-scroll" />  // overflow: 'scroll'
 ```
 
+## Opacity
+
+Named opacity utilities use the existing five-point percentage scale. Use an arbitrary raw value or percentage for an exact value:
+
+```tsx
+<View className="opacity-65" />       // opacity: 0.65
+<View className="opacity-[.67]" />    // opacity: 0.67
+<View className="opacity-[67%]" />    // opacity: 0.67
+```
+
+Arbitrary values must resolve to React Native's supported range from `0` through `1`.
+
 ## Display
 
 ```tsx

src/babel/plugin/visitors/className.test.ts

@@ -23,6 +23,20 @@ describe("className visitor - basic transformation", () => {
     expect(output).toContain("style:");
   });
 
+  it("should compile arbitrary opacity values", () => {
+    const input = `
+      import { View } from 'react-native';
+      export function Component() {
+        return <View className="opacity-[.67]" />;
+      }
+    `;
+
+    const output = transform(input, undefined, true);
+
+    expect(output).not.toContain("className");
+    expect(output).toContain("opacity: 0.67");
+  });
+
   it("should work with both tw and className in same file", () => {
     const input = `
       import { tw } from '@mgcrea/react-native-tailwind';

src/parser/layout.test.ts

@@ -294,6 +294,21 @@ describe("parseLayout - opacity utilities", () => {
     expect(parseLayout("opacity-90")).toEqual({ opacity: 0.9 });
     expect(parseLayout("opacity-95")).toEqual({ opacity: 0.95 });
   });
+
+  it("should parse arbitrary raw and percentage opacity values", () => {
+    expect(parseLayout("opacity-[.67]")).toEqual({ opacity: 0.67 });
+    expect(parseLayout("opacity-[0.125]")).toEqual({ opacity: 0.125 });
+    expect(parseLayout("opacity-[1]")).toEqual({ opacity: 1 });
+    expect(parseLayout("opacity-[67%]")).toEqual({ opacity: 0.67 });
+    expect(parseLayout("opacity-[12.5%]")).toEqual({ opacity: 0.125 });
+  });
+
+  it("should reject arbitrary opacity outside the native range", () => {
+    expect(parseLayout("opacity-[1.1]")).toBeNull();
+    expect(parseLayout("opacity-[101%]")).toBeNull();
+    expect(parseLayout("opacity-[-.1]")).toBeNull();
+    expect(parseLayout("opacity-[invalid]")).toBeNull();
+  });
 });
 
 describe("parseLayout - edge cases", () => {

src/parser/layout.ts

@@ -85,6 +85,33 @@ function parseArbitraryGrowShrink(value: string): number | null {
   return null;
 }
 
+/**
+ * Parse an arbitrary opacity value: [.67], [0.67], [1], [67%].
+ * React Native expects a normalized number from 0 to 1.
+ */
+function parseArbitraryOpacity(value: string): number | null {
+  const match = value.match(/^\[(\d+(?:\.\d*)?|\.\d+)(%)?\]$/);
+  if (match) {
+    const parsed = Number.parseFloat(match[1]);
+    const opacity = match[2] === "%" ? parsed / 100 : parsed;
+    if (opacity >= 0 && opacity <= 1) {
+      return opacity;
+    }
+  }
+
+  if (value.startsWith("[") && value.endsWith("]")) {
+    /* v8 ignore next 5 */
+    if (process.env.NODE_ENV !== "production") {
+      console.warn(
+        `[react-native-tailwind] Invalid arbitrary opacity value: ${value}. ` +
+          "Use a raw value from 0 to 1 or a percentage from 0% to 100% (e.g., [.67], [0.67], [67%]).",
+      );
+    }
+  }
+
+  return null;
+}
+
 // Display utilities
 const DISPLAY_MAP: Record<string, StyleObject> = {
   flex: { display: "flex" },
@@ -244,6 +271,13 @@ export function parseLayout(cls: string, customSpacing?: Record<string, number>)
   // Merge custom spacing with defaults for inset utilities
   const insetMap = customSpacing ? { ...INSET_SCALE, ...customSpacing } : INSET_SCALE;
 
+  if (cls.startsWith("opacity-")) {
+    const arbitraryOpacity = parseArbitraryOpacity(cls.substring(8));
+    if (arbitraryOpacity !== null) {
+      return { opacity: arbitraryOpacity };
+    }
+  }
+
   // Z-index: z-0, z-10, z-20, z-[999], etc.
   if (cls.startsWith("z-")) {
     const zKey = cls.substring(2);