refactor(lsp): register per-language semantics under lsp/semantic (#1687)

Python's highlighting hooks, member intentions and Implement Methods, and PHP's construct docs move under semantic/python and semantic/php behind a small registry of language-specific behaviour. Intentions now run only for the current document's language. Behaviour is otherwise unchanged; the generic language sets stay next to their users.

Co-authored-by: muutot <[email protected]>

src/editor/lsp/semantic/php/constructs.ts

@@ -0,0 +1,40 @@
+import type { EditorState } from "@codemirror/state";
+import { syntaxTree } from "@codemirror/language";
+
+const CONSTRUCTS: Readonly<Record<string, { signature: string; description: string }>> = {
+  empty: {
+    signature: "empty(mixed $var): bool",
+    description:
+      "Returns true when the value is falsey or the variable does not exist. Checking an undefined variable does not emit a warning.",
+  },
+  isset: {
+    signature: "isset(mixed $var, mixed ...$vars): bool",
+    description:
+      "Returns true only when every supplied variable exists and is not null. Checks stop at the first unset or null variable.",
+  },
+};
+
+export function phpConstructDocumentation(language: string | null, name: string): string | null {
+  if (language?.toLowerCase() !== "php") return null;
+  const key = name.toLowerCase();
+  const entry = Object.hasOwn(CONSTRUCTS, key) ? CONSTRUCTS[key] : undefined;
+  if (!entry) return null;
+  return [
+    "```php\n" + entry.signature + "\n```",
+    entry.description,
+    "PHP language construct; there is no source declaration to navigate to.",
+    `[PHP manual](https://www.php.net/manual/en/function.${key}.php)`,
+  ].join("\n\n");
+}
+
+/** Only an unqualified call, never a method, variable, string, comment or HTML text. */
+export function phpConstructAt(state: EditorState, pos: number, language: string | null) {
+  if (language?.toLowerCase() !== "php") return null;
+  for (const side of [-1, 1] as const) {
+    const node = syntaxTree(state).resolveInner(pos, side);
+    if (node.name !== "Name" || node.parent?.name !== "CallExpression" || node.parent.from !== node.from) continue;
+    const markdown = phpConstructDocumentation(language, state.sliceDoc(node.from, node.to));
+    if (markdown) return { from: node.from, to: node.to, markdown };
+  }
+  return null;
+}