Enables array completion with bracket notation (#9)

* Added tests the auto completion should adhere to

# Conflicts:
#	test/language-service/language-service.ts

* Array completion working

* Formatted

* Reverted spacing between braces

* Fixed properly with linter fix instead

* Raised package version

* Update lock file

---------

Co-authored-by: Melvin van Bree <m.vanbree@pro-fa.com>
Co-authored-by: Sander Toonen <s.toonen@pro-fa.com>

Author: 3 people

.editorconfig

@@ -6,4 +6,5 @@ end_of_line = lf
 charset = utf-8
 insert_final_newline = true
 trim_trailing_whitespace = true
-
+indent_style = space
+indent_size = 2

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@pro-fa/expr-eval",
-  "version": "6.0.0",
+  "version": "6.0.1",
   "description": "Mathematical expression evaluator",
   "keywords": [
     "expression",

package.json

@@ -19,7 +19,8 @@ export function valueTypeName(value: Value): string {
 }
 
 export function isPathChar(ch: string): boolean {
-  return /[A-Za-z0-9_$.]/.test(ch);
+  // Include square brackets to keep array selectors within the detected prefix
+  return /[A-Za-z0-9_$.\[\]]/.test(ch);
 }
 
 export function extractPathPrefix(text: string, position: number): { start: number; prefix: string } {

src/language-service/ls-utils.ts

@@ -1,5 +1,5 @@
 import { TextDocument } from 'vscode-languageserver-textdocument';
-import { Position, Range, MarkupKind, CompletionItem, CompletionItemKind } from 'vscode-languageserver-types';
+import { Position, Range, MarkupKind, CompletionItem, CompletionItemKind, InsertTextFormat } from 'vscode-languageserver-types';
 import { Values, Value, ValueObject } from '../types';
 import { TNAME, Token } from '../parsing';
 import { HoverV2 } from './language-service.types';
@@ -159,6 +159,72 @@ class VarTrie {
   }
 }
 
+/**
+ * Resolve value by a mixed dot/bracket path like foo[0][1].bar starting from a given root.
+ * For arrays, when an index is accessed, we treat it as the element shape and use the first element if present.
+ */
+function resolveValueByBracketPath(root: unknown, path: string): unknown {
+  const isObj = (v: unknown): v is Record<string, unknown> => v !== null && typeof v === 'object';
+  let node: unknown = root as unknown;
+  if (!path) return node;
+  const segments = path.split('.');
+  for (const seg of segments) {
+    if (!isObj(node)) return undefined;
+    // parse leading name and bracket chains
+    const i = seg.indexOf('[');
+    const name = i >= 0 ? seg.slice(0, i) : seg;
+    let rest = i >= 0 ? seg.slice(i) : '';
+    if (name) {
+      node = (node as Record<string, unknown>)[name];
+    }
+    // walk bracket chains, treat any index as the element shape (use first element)
+    while (rest.startsWith('[')) {
+      const closeIdx = rest.indexOf(']');
+      if (closeIdx < 0) break; // malformed, stop here
+      rest = rest.slice(closeIdx + 1);
+      if (Array.isArray(node)) {
+        node = node.length > 0 ? node[0] : undefined;
+      } else {
+        node = undefined;
+      }
+    }
+  }
+  return node;
+}
+
+/**
+ * Pushes standard key completion and (if applicable) an array selector snippet completion.
+ */
+function pushVarKeyCompletions(
+  items: CompletionItem[],
+  key: string,
+  label: string,
+  detail: string,
+  val: unknown,
+  rangePartial?: Range
+): void {
+  // Regular key/variable completion
+  items.push({
+    label,
+    kind: CompletionItemKind.Variable,
+    detail,
+    insertText: key,
+    textEdit: rangePartial ? { range: rangePartial, newText: key } : undefined
+  });
+
+  // If the value is an array, suggest selector snippet as an extra item
+  if (Array.isArray(val)) {
+    const snippet = key + '[${1}]';
+    items.push({
+      label: `${label}[]`,
+      kind: CompletionItemKind.Variable,
+      detail: 'array',
+      insertTextFormat: InsertTextFormat.Snippet,
+      textEdit: rangePartial ? { range: rangePartial, newText: snippet } : undefined
+    });
+  }
+}
+
 /**
  * Tries to resolve a variable hover using spans.
  * @param textDocument The document containing the variable name.
@@ -257,6 +323,27 @@ export function pathVariableCompletions(vars: Values | undefined, prefix: string
   const partial = endsWithDot ? '' : prefix.slice(lastDot + 1);
   const lowerPartial = partial.toLowerCase();
 
+  // If there are bracket selectors anywhere in the basePath, use bracket-aware resolution
+  if (basePath.includes('[')) {
+    const baseValue = resolveValueByBracketPath(vars, basePath);
+    const items: CompletionItem[] = [];
+
+    // If the baseValue is an object, offer its keys
+    if (baseValue && typeof baseValue === 'object' && !Array.isArray(baseValue)) {
+      const obj = baseValue as Record<string, unknown>;
+      for (const key of Object.keys(obj)) {
+        if (partial && !key.toLowerCase().startsWith(lowerPartial)) continue;
+        const fullLabel = basePath ? `${basePath}.${key}` : key;
+        const val = obj[key] as Value;
+        const detail = valueTypeName(val);
+        pushVarKeyCompletions(items, key, fullLabel, detail, val, rangePartial);
+      }
+    }
+
+    return items;
+  }
+
+  // Dot-only path: use trie for speed and existing behavior
   const baseNode = trie.search(baseParts);
   if (!baseNode) {
     return [];
@@ -272,14 +359,7 @@ export function pathVariableCompletions(vars: Values | undefined, prefix: string
     const child = baseNode.children[key];
     const label = [...baseParts, key].join('.');
     const detail = child.value !== undefined ? valueTypeName(child.value) : 'object';
-
-    items.push({
-      label,
-      kind: CompletionItemKind.Variable,
-      detail,
-      insertText: key,
-      textEdit: rangePartial ? { range: rangePartial, newText: key } : undefined
-    });
+    pushVarKeyCompletions(items, key, label, detail, child.value, rangePartial);
   }
 
   return items;

src/language-service/variable-utils.ts

@@ -205,6 +205,88 @@ describe('Language Service', () => {
       expect(completions.find(c => c.label === 'boolVar')?.detail).toBe('boolean');
       expect(completions.find(c => c.label === 'nullVar')?.detail).toBe('null');
     });
+
+    it('should suggest array selector when variable is an array', () => {
+      const text = 'arr';
+      const doc = TextDocument.create('file://test', 'plaintext', 1, text);
+
+      const completions = ls.getCompletions({
+        textDocument: doc,
+        variables: {
+          arr: [10, 20, 30]
+        },
+        position: { line: 0, character: 3 }
+      });
+
+      const arrayItem = completions.find(c => c.label === 'arr[]');
+      expect(arrayItem).toBeDefined();
+
+      // Insert only the selector
+      expect(arrayItem?.insertTextFormat).toBe(2); // Snippet
+      expect(arrayItem?.textEdit?.newText).toContain('arr[');
+    });
+
+    it('should autocomplete children after indexed array access', () => {
+      const text = 'arr[0].';
+      const doc = TextDocument.create('file://test', 'plaintext', 1, text);
+
+      const completions = ls.getCompletions({
+        textDocument: doc,
+        variables: {
+          arr: [
+            { foo: 1, bar: 2 }
+          ]
+        },
+        position: { line: 0, character: text.length }
+      });
+
+      expect(completions.length).toBeGreaterThan(0);
+
+      const fooItem = completions.find(c => c.label === 'arr[0].foo');
+      expect(fooItem).toBeDefined();
+      expect(fooItem?.insertText).toBe('foo');
+    });
+
+    it('should support multi-dimensional array selectors', () => {
+      const text = 'matrix[0][1].';
+      const doc = TextDocument.create('file://test', 'plaintext', 1, text);
+
+      const completions = ls.getCompletions({
+        textDocument: doc,
+        variables: {
+          matrix: [
+            [
+              { value: 42 }
+            ]
+          ]
+        },
+        position: { line: 0, character: text.length }
+      });
+
+      const valueItem = completions.find(c => c.label === 'matrix[0][1].value');
+      expect(valueItem).toBeDefined();
+      expect(valueItem?.insertText).toBe('value');
+    });
+
+    it('should place cursor inside array brackets', () => {
+      const text = 'arr';
+      const doc = TextDocument.create('file://test', 'plaintext', 1, text);
+
+      const completions = ls.getCompletions({
+        textDocument: doc,
+        variables: {
+          arr: [1, 2, 3]
+        },
+        position: { line: 0, character: 3 }
+      });
+
+      const arrayItem = completions.find(c => c.label === 'arr[]');
+      const newText = arrayItem?.textEdit?.newText as string | undefined;
+
+      expect(newText).toContain('[');
+      expect(newText).toContain(']');
+      expect(newText).toContain('${1}');
+    });
   });
 
   describe('getHover', () => {