feat: add isSafeUnquotedExpression

Author: gajus

README.md

@@ -19,6 +19,7 @@ Lightweight and performant Lucene-like parser, serializer and search engine.
   * [Boolean operators](#boolean-operators)
 * [Serializer](#serializer)
 * [AST](#ast)
+* [Utilities](#utilities)
 * [Compatibility with Lucene](#compatibility-with-lucene)
 * [Recipes](#recipes)
   * [Handling syntax errors](#handling-syntax-errors)
@@ -339,6 +340,21 @@ There are 11 AST tokens that describe a parsed Liqe query.
 
 If you are building a serializer, then you must implement all of them for the complete coverage of all possible query inputs. Refer to the [built-in serializer](./src/serialize.ts) for an example.
 
+## Utilities
+
+```ts
+import {
+  isSafeUnquotedExpression,
+} from 'liqe';
+
+/**
+ * Determines if an expression requires quotes.
+ * Use this if you need to programmatically manipulate the AST
+ * before using a serializer to convert the query back to text.
+ */
+isSafeUnquotedExpression(expression: string): boolean;
+```
+
 ## Compatibility with Lucene
 
 The following Lucene abilities are not supported:

src/Liqe.ts

@@ -35,3 +35,6 @@ export {
 export {
   serialize,
 } from './serialize';
+export {
+  isSafeUnquotedExpression,
+} from './isSafeUnquotedExpression';

src/isSafeUnquotedExpression.ts

@@ -0,0 +1,3 @@
+export const isSafeUnquotedExpression = (expression: string): boolean => {
+  return /^[#$*@A-Z_a-z][#$*.@A-Z_a-z-]*$/.test(expression);
+};

test/liqe/isSafeUnquotedExpression.ts

@@ -0,0 +1,12 @@
+import test from 'ava';
+import {
+  isSafeUnquotedExpression,
+} from '../../src/isSafeUnquotedExpression';
+
+const testExpression = (t, expected) => {
+  t.is(isSafeUnquotedExpression(t.title), expected);
+};
+
+test('foo', testExpression, true);
+
+test('.foo', testExpression, false);