feat: allow to configure transient props

Allow to configure transient props for a specific component using the
`transientProps` constructor.

Closes #29

src/index.test.tsx

@@ -131,16 +131,34 @@ describe("twc", () => {
 
   test("accepts a function to define className", () => {
     type Props = {
-      size: "sm" | "lg";
+      $size: "sm" | "lg";
       children: React.ReactNode;
     };
     const Title = twc.h1<Props>((props) => ({
-      "text-xl": props.size === "lg",
-      "text-sm": props.size === "sm",
+      "text-xl": props.$size === "lg",
+      "text-sm": props.$size === "sm",
     }));
-    render(<Title size="sm">Title</Title>);
+    render(<Title $size="sm">Title</Title>);
     const title = screen.getByText("Title");
     expect(title).toBeDefined();
+    expect(title.getAttribute("$size")).toBe(null);
+    expect(title.tagName).toBe("H1");
+    expect(title.classList.contains("text-sm")).toBe(true);
+  });
+
+  test("allows to customize transient props", () => {
+    type Props = {
+      xsize: "sm" | "lg";
+      children: React.ReactNode;
+    };
+    const Title = twc.h1.transientProps(["xsize"])<Props>((props) => ({
+      "text-xl": props.xsize === "lg",
+      "text-sm": props.xsize === "sm",
+    }));
+    render(<Title xsize="sm">Title</Title>);
+    const title = screen.getByText("Title");
+    expect(title).toBeDefined();
+    expect(title.getAttribute("xsize")).toBe(null);
     expect(title.tagName).toBe("H1");
     expect(title.classList.contains("text-sm")).toBe(true);
   });

src/index.tsx

@@ -50,13 +50,23 @@ type FirstLevelTemplate<
   TCompose extends AbstractCompose,
   TExtraProps,
 > = Template<TComponent, TCompose, TExtraProps> & {
+  /**
+   * Add additional props to the component.
+   */
   attrs: <TProps = undefined>(
     attrs:
       | Record<string, any>
       | ((
           props: ResultProps<TComponent, TProps, TExtraProps, TCompose>,
         ) => Record<string, any>),
   ) => Template<TComponent, TCompose, TExtraProps, TProps>;
+} & {
+  /**
+   * Prevent props from being forwarded to the component.
+   */
+  transientProps: (
+    fn: string[] | ((prop: string) => boolean),
+  ) => FirstLevelTemplate<TComponent, TCompose, TExtraProps>;
 };
 
 type Twc<TCompose extends AbstractCompose> = (<T extends React.ElementType>(
@@ -69,8 +79,6 @@ type Twc<TCompose extends AbstractCompose> = (<T extends React.ElementType>(
   >;
 };
 
-type ShouldForwardProp = (prop: string) => boolean;
-
 export type TwcComponentProps<
   TComponent extends React.ElementType,
   TCompose extends AbstractCompose = typeof clsx,
@@ -85,12 +93,12 @@ export type Config<TCompose extends AbstractCompose> = {
    * The function to use to determine if a prop should be forwarded to the
    * underlying component. Defaults to `prop => prop[0] !== "$"`.
    */
-  shouldForwardProp?: ShouldForwardProp;
+  shouldForwardProp?: (prop: string) => boolean;
 };
 
 function filterProps(
   props: Record<string, any>,
-  shouldForwardProp: ShouldForwardProp,
+  shouldForwardProp: (prop: string) => boolean,
 ) {
   const filteredProps: Record<string, any> = {};
   const keys = Object.keys(props);
@@ -109,10 +117,13 @@ export const createTwc = <TCompose extends AbstractCompose = typeof clsx>(
   config: Config<TCompose> = {},
 ) => {
   const compose = config.compose || clsx;
-  const shouldForwardProp =
+  const defaultShouldForwardProp =
     config.shouldForwardProp || ((prop) => prop[0] !== "$");
   const wrap = (Component: React.ElementType) => {
-    const createTemplate = (attrs?: Attributes) => {
+    const createTemplate = (
+      attrs?: Attributes,
+      shouldForwardProp = defaultShouldForwardProp,
+    ) => {
       const template = (
         stringsOrFn: TemplateStringsArray | Function,
         ...values: any[]
@@ -147,6 +158,16 @@ export const createTwc = <TCompose extends AbstractCompose = typeof clsx>(
         });
       };
 
+      template.transientProps = (
+        fnOrArray: string[] | ((prop: string) => boolean),
+      ) => {
+        const shouldForwardProp =
+          typeof fnOrArray === "function"
+            ? (prop: string) => !fnOrArray(prop)
+            : (prop: string) => !fnOrArray.includes(prop);
+        return createTemplate(attrs, shouldForwardProp);
+      };
+
       if (attrs === undefined) {
         template.attrs = (attrs: Attributes) => {
           return createTemplate(attrs);

website/pages/docs/guides/adapting-based-on-props.mdx

@@ -30,7 +30,7 @@ return props accepted by a `twc` component. It's similar to `React.ComponentProp
 <details>
   <summary>Why is the prop prefixed by a dollar?</summary>
 
-We call the prop `$primary` a "transient prop", transient props can be consumed by the components but are not passed to the underlying components. It our case, it means the `<button>` will not get a `<button $primary="true">` attribute in the DOM.
+We call the prop `$primary` a "transient prop". A transient prop starts with a `$`, it can be consumed by the uppermost component layer but are not passed to the underlying components. It our case, it means the `<button>` will not get a `<button $primary="true">` attribute in the DOM.
 
 </details>
 
@@ -66,3 +66,49 @@ export default () => (
   </div>
 );
 ```
+
+## Customize transient props
+
+By default, all props starting with a `$` are considered _transient_. This is a is a hint that it is meant exclusively for the uppermost component layer and should not be passed further down. In other terms, it prevents your DOM element to have unexpected props.
+
+If you don't like the `$` prefix, you can customize transient props for a specific component using `transientProps` constructor.
+
+```tsx {8} /props/ /$primary/
+import { twc, TwcComponentProps } from "react-twc";
+
+type ButtonProps = TwcComponentProps<"button"> & { primary?: boolean };
+
+// The "primary" prop is marked as transient
+const Button = twc.button.transientProps(["primary"])<ButtonProps>((props) => [
+  "font-semibold border border-blue-500 rounded",
+  props.primary ? "bg-blue-500 text-white" : "bg-white text-gray-800",
+]);
+
+export default () => (
+  <div>
+    <Button>Normal</Button>
+    <Button primary>Primary</Button>
+  </div>,
+);
+```
+
+`transientProps` also accepts a function:
+
+```tsx
+const Button = twc.button.transientProps(
+  (prop) => prop === "primary",
+)<ButtonProps>((props) => [
+  "font-semibold border border-blue-500 rounded",
+  props.primary ? "bg-blue-500 text-white" : "bg-white text-gray-800",
+]);
+```
+
+It is also possible to configure this behaviour globally by creating a custom instance of `twc`:
+
+```ts filename="utils.ts" {11}
+import { clsx } from "clsx";
+import { createTwc } from "react-twc";
+
+// Forward all props not starting by "_"
+export const twx = createTwc({ shouldForwardProp: (prop) => prop[0] !== "_" });
+```