feat(dashboard): scope-aware autocomplete for user-defined symbols

Adds a second CompletionSource that reads the Rhai parser's symbol
table. On a plain word it surfaces in-scope `let`/`const`/`fn` names
(with the function signature in the popup's detail line); on `obj.`
it suggests the field names of an object-map literal that initialized
`obj`. Composes with the existing static `ctx.*` / `log::*` source via
`autocompletion({ override: [scopeCompletionSource, rhaiCompletions] })`,
which CodeMirror merges. The static source now bows out on generic
`name.` rather than flooding the popup with keywords.

A new StateField caches one parse + symbol-table per editor state and
rebuilds on doc change. Bundle delta: +18 KB raw, +4.7 KB gzipped.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/src/lib/rhai-mode.ts

@@ -16,6 +16,8 @@
 
 import { StreamLanguage, LanguageSupport } from '@codemirror/language';
 import { autocompletion, type CompletionContext, type CompletionResult } from '@codemirror/autocomplete';
+import { StateField, type Extension } from '@codemirror/state';
+import { parse, buildSymbolTable, type ParseResult, type SymbolTable } from './rhai';
 
 // Keywords that drive control flow (`if`, `for`, ...) — these get the
 // `controlKeyword` tag so the theme can color them distinctly from
@@ -297,6 +299,11 @@ export function rhaiCompletions(context: CompletionContext): CompletionResult |
 		};
 	}
 
+	// Member access on something other than `ctx`/`log` — let the
+	// script-aware source decide whether it has fields to offer. We bow
+	// out so we don't flood the popup with keywords after a `.`.
+	if (context.matchBefore(/\.\w*$/)) return null;
+
 	// Plain word at the cursor → keywords + top-level names.
 	const word = context.matchBefore(/\w+/);
 	if (!word && !context.explicit) return null;
@@ -307,6 +314,92 @@ export function rhaiCompletions(context: CompletionContext): CompletionResult |
 	};
 }
 
-export function rhai(): LanguageSupport {
-	return new LanguageSupport(rhaiLanguage, [autocompletion({ override: [rhaiCompletions] })]);
+// ---------------------------------------------------------------------------
+// Script-aware analysis
+// ---------------------------------------------------------------------------
+
+// One AST + symbol table per editor state. Rebuilt on every doc change.
+// Scripts in the dashboard are small (20–200 lines is the target); the
+// parse + walk is sub-millisecond at that size, so we don't bother
+// debouncing for now.
+interface RhaiAnalysis {
+	parse: ParseResult;
+	table: SymbolTable;
+}
+
+function analyze(source: string): RhaiAnalysis {
+	const parsed = parse(source);
+	return { parse: parsed, table: buildSymbolTable(parsed) };
+}
+
+export const rhaiAnalysisField = StateField.define<RhaiAnalysis>({
+	create: (state) => analyze(state.doc.toString()),
+	update: (value, tr) => (tr.docChanged ? analyze(tr.newDoc.toString()) : value)
+});
+
+/**
+ * Script-aware completion source.
+ *
+ * Two things on top of the static `ctx.*` / `log::*` list:
+ *   1. After `name.`, if `name` was initialized to an object-map
+ *      literal, suggest that literal's field names.
+ *   2. At a plain word position, suggest user-defined symbols in scope
+ *      (locals, function parameters, top-level `fn` decls). `fn` decls
+ *      get their signature in the `detail` field so the popup shows
+ *      `process(order, user)` rather than just `process`.
+ *
+ * Composes with `rhaiCompletions` via `autocompletion({ override:
+ * [scopeCompletionSource, rhaiCompletions] })` — CodeMirror merges the
+ * results.
+ */
+export function scopeCompletionSource(context: CompletionContext): CompletionResult | null {
+	const analysis = context.state.field(rhaiAnalysisField, false);
+	if (!analysis) return null;
+
+	// Member access — `obj.fie|`. Only fire if `obj` resolves to a known
+	// object-literal in scope; otherwise leave the popup empty rather
+	// than guess wrong fields.
+	const member = context.matchBefore(/(\w+)\.(\w*)/);
+	if (member) {
+		const dotIdx = member.text.indexOf('.');
+		const objectName = member.text.slice(0, dotIdx);
+		// `ctx.*` is handled by the static source — don't double up.
+		if (objectName !== 'ctx') {
+			const fields = analysis.table.objectFieldsOf(objectName, member.from);
+			if (fields.length > 0) {
+				return {
+					from: member.from + dotIdx + 1,
+					options: fields.map((label) => ({ label, type: 'property' })),
+					validFor: /^\w*$/
+				};
+			}
+		}
+		return null;
+	}
+
+	// Skip when right after `::` (handled by the static source for log::).
+	if (context.matchBefore(/::\w*$/)) return null;
+
+	// Plain word — surface in-scope decls.
+	const word = context.matchBefore(/\w+/);
+	if (!word && !context.explicit) return null;
+	const decls = analysis.table.scopeCompletions(context.pos);
+	if (decls.length === 0) return null;
+	return {
+		from: word ? word.from : context.pos,
+		options: decls.map((d) => ({
+			label: d.name,
+			type: d.kind === 'fn' ? 'function' : 'variable',
+			detail: d.signature ?? d.kind
+		})),
+		validFor: /^\w*$/
+	};
+}
+
+export function rhai(): LanguageSupport {
+	const extensions: Extension[] = [
+		rhaiAnalysisField,
+		autocompletion({ override: [scopeCompletionSource, rhaiCompletions] })
+	];
+	return new LanguageSupport(rhaiLanguage, extensions);
 }