feat: Add pseudos option

This option allows users to specify pseudo-classes for

README.md

@@ -144,6 +144,7 @@ All options are optional.
     sometimes greatly improving querying performance. Disable this if your
     document can change in between queries with the same compiled selector.
     Default: `true`.
+-   `pseudos`: A map of pseudo-selectors to functions or strings.
 
 #### Custom Adapters
 

src/index.ts

@@ -198,4 +198,5 @@ export function is<Node, ElementNode extends Node>(
 export default selectAll;
 
 // Export filters, pseudos and aliases to allow users to supply their own.
+/** @deprecated Use the `pseudos` option instead. */
 export { filters, pseudos, aliases } from "./pseudo-selectors/index.js";

src/pseudo-selectors/index.ts

@@ -12,7 +12,6 @@
  * of `next()` and your code.
  * Pseudos should be used to implement simple checks.
  */
-import boolbase from "boolbase";
 import type { CompiledQuery, InternalOptions, CompileToken } from "../types.js";
 import { parse, PseudoSelector } from "css-what";
 import { filters } from "./filters.js";
@@ -38,27 +37,38 @@ export function compilePseudoSelector<Node, ElementNode extends Node>(
 
         return subselects[name](next, data, options, context, compileToken);
     }
-    if (name in aliases) {
+
+    const userPseudo = options.pseudos?.[name];
+
+    const stringPseudo =
+        typeof userPseudo === "string" ? userPseudo : aliases[name];
+
+    if (typeof stringPseudo === "string") {
         if (data != null) {
             throw new Error(`Pseudo ${name} doesn't have any arguments`);
         }
 
         // The alias has to be parsed here, to make sure options are respected.
-        const alias = parse(aliases[name]);
+        const alias = parse(stringPseudo);
         return subselects["is"](next, alias, options, context, compileToken);
     }
+
+    if (typeof userPseudo === "function") {
+        verifyPseudoArgs(userPseudo, name, data, 1);
+
+        return (elem) => userPseudo(elem, data) && next(elem);
+    }
+
     if (name in filters) {
         return filters[name](next, data as string, options, context);
     }
+
     if (name in pseudos) {
         const pseudo = pseudos[name];
-        verifyPseudoArgs(pseudo, name, data);
+        verifyPseudoArgs(pseudo, name, data, 2);
 
-        return pseudo === boolbase.falseFunc
-            ? boolbase.falseFunc
-            : next === boolbase.trueFunc
-            ? (elem) => pseudo(elem, options, data)
-            : (elem) => pseudo(elem, options, data) && next(elem);
+        return (elem) => pseudo(elem, options, data) && next(elem);
     }
+
     throw new Error(`Unknown pseudo-class :${name}`);
 }

src/pseudo-selectors/pseudos.ts

@@ -4,7 +4,7 @@ import type { InternalOptions } from "../types.js";
 export type Pseudo = <Node, ElementNode extends Node>(
     elem: ElementNode,
     options: InternalOptions<Node, ElementNode>,
-    subselect?: ElementNode | string | null
+    subselect?: string | null
 ) => boolean;
 
 // While filters are precompiled, pseudos get called when they are needed
@@ -92,16 +92,17 @@ export const pseudos: Record<string, Pseudo> = {
     },
 };
 
-export function verifyPseudoArgs(
-    func: Pseudo,
+export function verifyPseudoArgs<T extends Array<unknown>>(
+    func: (...args: T) => boolean,
     name: string,
-    subselect: PseudoSelector["data"]
+    subselect: PseudoSelector["data"],
+    argIndex: number
 ): void {
     if (subselect === null) {
-        if (func.length > 2) {
-            throw new Error(`pseudo-selector :${name} requires an argument`);
+        if (func.length > argIndex) {
+            throw new Error(`Pseudo-class :${name} requires an argument`);
         }
-    } else if (func.length === 2) {
-        throw new Error(`pseudo-selector :${name} doesn't have any arguments`);
+    } else if (func.length === argIndex) {
+        throw new Error(`Pseudo-class :${name} doesn't have any arguments`);
     }
 }

src/types.ts

@@ -127,6 +127,18 @@ export interface Options<Node, ElementNode extends Node> {
      * @default false
      */
     quirksMode?: boolean;
+    /**
+     * Pseudo-classes that override the default ones.
+     *
+     * Maps from names to either strings of functions.
+     * - A string value is a selector that the element must match to be selected.
+     * - A function is called with the element as its first argument, and optional
+     *  parameters second. If it returns true, the element is selected.
+     */
+    pseudos?: Record<
+        string,
+        string | ((elem: ElementNode, value?: string | null) => boolean)
+    >;
     /**
      * The last function in the stack, will be called with the last element
      * that's looked at.

test/api.ts

@@ -127,6 +127,24 @@ describe("API", () => {
 
             delete CSSselect.pseudos["foovalue"];
         });
+
+        it("should throw if parameter is supplied for user-provided pseudo", () =>
+            expect(() =>
+                CSSselect.compile(":foovalue(boo)", {
+                    pseudos: { foovalue: "tag" },
+                })
+            ).toThrow("doesn't have any arguments"));
+
+        it("should throw if no parameter is supplied for user-provided pseudo", () =>
+            expect(() =>
+                CSSselect.compile(":foovalue", {
+                    pseudos: {
+                        foovalue(_el, data) {
+                            return data != null;
+                        },
+                    },
+                })
+            ).toThrow("requires an argument"));
     });
 
     describe("unsatisfiable and universally valid selectors", () => {