Configurable language parsing

README.md

@@ -18,10 +18,20 @@ import { lintExpression } from "@bpmn-io/feel-lint"
 lintExpression('foo = bar');
 ```
 
-### Codemirror plugin
+You may pass custom language configuration to the editor:
 
-The `cmFeelLinter` function returns a codemirror linting source that you can use as a extension
-in you codemirror instance.
+```javascript
+lintExpression('> 10, "yes", mike\'s name', {
+  dialect: 'unaryTests',
+  context: {
+    "mike's name": "Mike the might"
+  }
+});
+```
+
+### CodeMirror plugin
+
+The `cmFeelLinter` function returns a [`LintSource`](https://codemirror.net/docs/ref/#lint.LintSource) that you can use to extend your [CodeMirror](https://codemirror.net/) instance.
 
 ```javascript
 import { cmFeelLinter } from "@bpmn-io/feel-lint"

lib/text/index.js

@@ -1,15 +1,26 @@
-import { parser } from 'lezer-feel';
+import { parser, trackVariables } from 'lezer-feel';
 import lintAll from '../shared/index.js';
 
 /**
  * Create an array of syntax errors for the given expression.
  *
  * @param {String} expression
+ * @param { {
+ *   dialect?: 'expression' | 'unaryTests',
+ *   context?: Record<string, any>
+ * } } [lintOptions]
+ *
  * @returns {LintMessage[]} array of syntax errors
  */
-export function lintExpression(expression) {
+export function lintExpression(expression, {
+  dialect = 'expression',
+  context = {}
+} = {}) {
 
-  const syntaxTree = parser.parse(expression);
+  const syntaxTree = parser.configure({
+    top: dialect === 'unaryTests' ? 'UnaryTests' : 'Expression',
+    contextTracker: trackVariables(context)
+  }).parse(expression);
 
   const lintMessages = lintAll(syntaxTree);