feat: expose escapeODataStringLiteral and escapeIllegalChars

Splits the internal `escapeIllegalChars` helper into two layers and
exposes both as public exports:

- `escapeODataStringLiteral` — doubles single quotes per OData v4 string
  literal escape rules; returns the raw escaped value
- `escapeIllegalChars` — composes the above with `encodeURIComponent`
  for URL-safe values; previously private, behaviour unchanged

Consumers who interpolate values into OData filter templates as strings
(rather than going through `buildQuery`'s structured filter API) need
the raw escape primitive without URL encoding — they can now use the
public export instead of reaching into internals.

Author: mzpkdev

.changeset/eager-otters-escape.md

@@ -0,0 +1,5 @@
+---
+"odata-query": minor
+---
+
+- feat: expose `escapeODataStringLiteral` and `escapeIllegalChars` as public exports

src/index.ts

@@ -306,9 +306,12 @@ function getStringCollectionClause(lambdaParameter: string, value: any, collecti
   return `${propName}/${collectionOperator}(${lambdaParameter}: ${lambdaParameter} ${conditionOperator} '${value}')`;
 }
 
-function escapeIllegalChars(string: string) {
-  string = string.replace(/'/g, "''");
-  return encodeURIComponent(string);
+export function escapeODataStringLiteral(string: string): string {
+  return string.replace(/'/g, "''");
+}
+
+export function escapeIllegalChars(string: string): string {
+  return encodeURIComponent(escapeODataStringLiteral(string));
 }
 
 function buildFilter<T>(filters: Filter<T> = {}, aliases: Alias[] = [], propPrefix = ''): string {

test/index.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test as it } from 'vitest'
 
-import buildQuery, {Expand, OrderBy, alias, json, ITEM_ROOT, decimal, TypedFilter} from '../src/index';
+import buildQuery, {Expand, OrderBy, alias, json, ITEM_ROOT, decimal, TypedFilter, escapeODataStringLiteral, escapeIllegalChars} from '../src/index';
 import { Square } from './test-interface'; 
 
 it('should return an empty string by default', () => {
@@ -1881,3 +1881,77 @@ describe('format', () => {
     expect(actual).toEqual(expected);
   });
 });
+
+describe('escapeODataStringLiteral', () => {
+  it('should return plain strings unchanged', () => {
+    const value = 'Hello';
+    const expected = 'Hello';
+    const actual = escapeODataStringLiteral(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should return an empty string unchanged', () => {
+    const value = '';
+    const expected = '';
+    const actual = escapeODataStringLiteral(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should double a single quote', () => {
+    const value = "O'Brien";
+    const expected = "O''Brien";
+    const actual = escapeODataStringLiteral(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should double every quote when multiple are present', () => {
+    const value = "'a'b'";
+    const expected = "''a''b''";
+    const actual = escapeODataStringLiteral(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should not URL-encode reserved characters', () => {
+    const value = 'a&b#c d';
+    const expected = 'a&b#c d';
+    const actual = escapeODataStringLiteral(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should preserve unicode characters as-is', () => {
+    const value = 'café';
+    const expected = 'café';
+    const actual = escapeODataStringLiteral(value);
+    expect(actual).toEqual(expected);
+  });
+});
+
+describe('escapeIllegalChars', () => {
+  it('should not URL-encode single quotes', () => {
+    const value = "O'Brien";
+    const expected = "O''Brien";
+    const actual = escapeIllegalChars(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should URL-encode reserved characters', () => {
+    const value = 'a&b#c d';
+    const expected = 'a%26b%23c%20d';
+    const actual = escapeIllegalChars(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should double quotes and URL-encode reserved characters', () => {
+    const value = "O'Brien & co";
+    const expected = "O''Brien%20%26%20co";
+    const actual = escapeIllegalChars(value);
+    expect(actual).toEqual(expected);
+  });
+
+  it('should equal encodeURIComponent of escapeODataStringLiteral', () => {
+    const value = "O'Brien & co";
+    const expected = encodeURIComponent(escapeODataStringLiteral(value));
+    const actual = escapeIllegalChars(value);
+    expect(actual).toEqual(expected);
+  });
+});