feat: add autocmd source for vim autocmds

Implements a new source that lists all defined vim autocmds with their
events, patterns, and commands. Supports filtering by event and group,
and can include or exclude buffer-local autocmds.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: lambdalisue

builtin/source/autocmd.ts

@@ -0,0 +1,176 @@
+import { defineSource, type Source } from "../../source.ts";
+
+type Detail = {
+  /**
+   * Autocmd event name
+   */
+  event: string;
+
+  /**
+   * Autocmd group name (if any)
+   */
+  group?: string;
+
+  /**
+   * Pattern the autocmd matches
+   */
+  pattern: string;
+
+  /**
+   * Command to execute
+   */
+  command: string;
+
+  /**
+   * Whether it's a buffer-local autocmd
+   */
+  bufferLocal: boolean;
+
+  /**
+   * Additional autocmd flags/attributes
+   */
+  flags: string[];
+};
+
+export type AutocmdOptions = {
+  /**
+   * Filter by specific event(s).
+   */
+  events?: string[];
+
+  /**
+   * Filter by autocmd group.
+   */
+  group?: string;
+
+  /**
+   * Whether to include buffer-local autocmds.
+   * @default true
+   */
+  includeBufferLocal?: boolean;
+
+  /**
+   * Whether to show detailed command (full command vs truncated).
+   * @default false
+   */
+  showFullCommand?: boolean;
+};
+
+/**
+ * Creates a Source that generates items from Vim autocmds.
+ *
+ * This Source retrieves all defined autocmds and generates items
+ * for each one, showing their events, patterns, and commands.
+ *
+ * @param options - Options to customize autocmd listing.
+ * @returns A Source that generates items representing autocmds.
+ */
+export function autocmd(
+  options: Readonly<AutocmdOptions> = {},
+): Source<Detail> {
+  const filterEvents = options.events;
+  const filterGroup = options.group;
+  const includeBufferLocal = options.includeBufferLocal ?? true;
+  const showFullCommand = options.showFullCommand ?? false;
+
+  return defineSource(async function* (denops, _params, { signal }) {
+    // Get autocmd output
+    const autocmdCmd = filterGroup ? `:autocmd ${filterGroup}` : ":autocmd";
+    const output = await denops.call("execute", autocmdCmd) as string;
+    signal?.throwIfAborted();
+
+    // Parse autocmd output
+    const lines = output.trim().split("\n");
+    const items: Array<{
+      id: number;
+      value: string;
+      detail: Detail;
+    }> = [];
+
+    let id = 0;
+    let currentGroup = "";
+    let currentEvent = "";
+
+    for (const line of lines) {
+      const trimmed = line.trim();
+      if (!trimmed) continue;
+
+      // Check for group header
+      const groupMatch = trimmed.match(/^--- Autocommands ---$/);
+      if (groupMatch) {
+        currentGroup = "";
+        continue;
+      }
+
+      // Check for named group header
+      const namedGroupMatch = trimmed.match(
+        /^(\w+)\s+Autocommands for "(.+)"$/,
+      );
+      if (namedGroupMatch) {
+        currentGroup = namedGroupMatch[1];
+        continue;
+      }
+
+      // Check for event header
+      const eventMatch = trimmed.match(/^(\w+)$/);
+      if (eventMatch && !trimmed.includes(" ")) {
+        currentEvent = eventMatch[1];
+        continue;
+      }
+
+      // Parse autocmd line
+      // Format: "    pattern    command"
+      const cmdMatch = trimmed.match(/^\s*(\S+)\s+(.+)$/);
+      if (cmdMatch && currentEvent) {
+        const [, pattern, command] = cmdMatch;
+
+        // Filter by event if specified
+        if (filterEvents && !filterEvents.includes(currentEvent)) {
+          continue;
+        }
+
+        // Parse flags from pattern
+        const flags: string[] = [];
+        let bufferLocal = false;
+        let cleanPattern = pattern;
+
+        // Check for buffer-local indicator
+        if (pattern.startsWith("<buffer>")) {
+          bufferLocal = true;
+          cleanPattern = pattern.replace("<buffer>", "").trim();
+          flags.push("buffer");
+        }
+
+        // Skip buffer-local if not included
+        if (bufferLocal && !includeBufferLocal) {
+          continue;
+        }
+
+        // Format display value
+        const groupStr = currentGroup ? `[${currentGroup}] ` : "";
+        const bufferStr = bufferLocal ? " <buffer>" : "";
+        const truncatedCmd = showFullCommand || command.length <= 50
+          ? command
+          : command.substring(0, 47) + "...";
+
+        const value =
+          `${groupStr}${currentEvent} ${cleanPattern}${bufferStr} → ${truncatedCmd}`;
+
+        items.push({
+          id: id++,
+          value,
+          detail: {
+            event: currentEvent,
+            group: currentGroup || undefined,
+            pattern: cleanPattern,
+            command,
+            bufferLocal,
+            flags,
+          },
+        });
+      }
+    }
+
+    yield* items;
+  });
+}