From ec05bd95d25f4a238b081e00fa2a68f0e5efb034 Mon Sep 17 00:00:00 2001
From: eagletrhost <dimazanugrah12@gmail.com>
Date: Wed, 10 Dec 2025 23:33:45 +1100
Subject: [PATCH] fix: set up default jsx context for operations

---
 .../preprocess-jsx-expressions.test.ts        | 37 +++++++++++++++++++
 lib/mdxish.ts                                 |  4 +-
 .../mdxish/preprocess-jsx-expressions.ts      | 14 ++++++-
 3 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/__tests__/transformers/preprocess-jsx-expressions.test.ts b/__tests__/transformers/preprocess-jsx-expressions.test.ts
index fcf0fd88b..6f5012c35 100644
--- a/__tests__/transformers/preprocess-jsx-expressions.test.ts
+++ b/__tests__/transformers/preprocess-jsx-expressions.test.ts
@@ -1,6 +1,43 @@
+import { mix } from '../../lib';
 import { preprocessJSXExpressions } from '../../processor/transform/mdxish/preprocess-jsx-expressions';
 
 describe('preprocessJSXExpressions', () => {
+  describe('using the default jsx context', () => {
+    it('should evaluate the string operations', () => {
+      const content = 'Hello {uppercase("world")} {lowercase("WORLD")}';
+      const result = mix(content);
+      expect(result).toContain('Hello WORLD world');
+      expect(result).not.toContain('{uppercase("world")}');
+      expect(result).not.toContain('{lowercase("WORLD")}');
+    });
+
+    it('should evaluate the number operations when the operations are mentioned', () => {
+      const content = 'Hello {add(1, 2)} {subtract(3, 4)} {multiply(5, 6)} {divide(4, 2)}';
+      const result = mix(content);
+      expect(result).toContain('Hello 3 -1 30 2');
+      expect(result).not.toContain('{add(1, 2)}');
+      expect(result).not.toContain('{subtract(3, 4)}');
+      expect(result).not.toContain('{multiply(5, 6)}');
+      expect(result).not.toContain('{divide(4, 2)}');
+    });
+
+    it('should evaluate number operations when math symbols are used', () => {
+      const content = '{1 + 2 - 1} {4 * 2 / 2}';
+      const result = mix(content);
+      expect(result).toContain('2 4');
+      expect(result).not.toContain('{1 + 2 - 1}');
+      expect(result).not.toContain('{4 * 2 / 2}');
+    });
+
+    it('should not evaluate operations when not in braces', () => {
+      const content = '1 + 2 uppercase("world")';
+      const result = mix(content);
+      expect(result).toContain(content);
+      expect(result).not.toContain('WORLD');
+      expect(result).not.toContain('3');
+    });
+  });
+
   describe('Step 3: Evaluate attribute expressions', () => {
     it('should evaluate JSX attribute expressions and convert them to string attributes', () => {
       const context = {
diff --git a/lib/mdxish.ts b/lib/mdxish.ts
index c20b5caf1..2f3fc1543 100644
--- a/lib/mdxish.ts
+++ b/lib/mdxish.ts
@@ -24,7 +24,7 @@ import mdxishComponentBlocks from '../processor/transform/mdxish/mdxish-componen
 import mdxishHtmlBlocks from '../processor/transform/mdxish/mdxish-html-blocks';
 import magicBlockRestorer from '../processor/transform/mdxish/mdxish-magic-blocks';
 import mdxishTables from '../processor/transform/mdxish/mdxish-tables';
-import { preprocessJSXExpressions, type JSXContext } from '../processor/transform/mdxish/preprocess-jsx-expressions';
+import { preprocessJSXExpressions, type JSXContext, DEFAULT_JSX_CONTEXT } from '../processor/transform/mdxish/preprocess-jsx-expressions';
 import variablesTextTransformer from '../processor/transform/mdxish/variables-text';
 import tailwindTransformer from '../processor/transform/tailwind';
 
@@ -46,7 +46,7 @@ const defaultTransformers = [calloutTransformer, codeTabsTransformer, gemojiTran
  * @see {@link https://github.com/readmeio/rmdx/blob/main/docs/mdxish-flow.md}
  */
 export function mdxish(mdContent: string, opts: MdxishOpts = {}): Root {
-  const { components: userComponents = {}, jsxContext = {}, useTailwind } = opts;
+  const { components: userComponents = {}, jsxContext = DEFAULT_JSX_CONTEXT, useTailwind } = opts;
 
   const components: CustomComponents = {
     ...loadComponents(),
diff --git a/processor/transform/mdxish/preprocess-jsx-expressions.ts b/processor/transform/mdxish/preprocess-jsx-expressions.ts
index 3fe2c9cf3..03f8a1a3b 100644
--- a/processor/transform/mdxish/preprocess-jsx-expressions.ts
+++ b/processor/transform/mdxish/preprocess-jsx-expressions.ts
@@ -2,9 +2,21 @@
  * Pre-processes JSX-like expressions before markdown parsing.
  * Converts href={'value'} to href="value", evaluates {expressions}, etc.
  */
-
 export type JSXContext = Record<string, unknown>;
 
+// Common operations that might be used in JSX expressions
+// These are not exhaustive, but are a good starting point
+// We probably want to just use a library that'll load most of the common operations for us
+export const DEFAULT_JSX_CONTEXT: JSXContext = {
+  uppercase: (value: string) => value.toUpperCase(),
+  lowercase: (value: string) => value.toLowerCase(),
+
+  add: (a: number, b: number) => a + b,
+  subtract: (a: number, b: number) => a - b,
+  multiply: (a: number, b: number) => a * b,
+  divide: (a: number, b: number) => a / b,
+};
+
 // Base64 encode (Node.js + browser compatible)
 function base64Encode(str: string): string {
   if (typeof Buffer !== 'undefined') {