From 43ad6db0ddeefb7e9150f9e0271bf18c9efddfa9 Mon Sep 17 00:00:00 2001
From: James Garbutt <43081j@users.noreply.github.com>
Date: Fri, 28 Nov 2025 20:47:18 +0000
Subject: [PATCH] feat: add exponentiation

Adds a `Math.pow(a, b)` to `a ** b` codemod.
---
 .../__snapshots__/exponentiation.test.ts.snap | 27 +++++++++
 src/codemods/exponentiation.test.ts           | 57 +++++++++++++++++++
 src/codemods/exponentiation.ts                | 51 +++++++++++++++++
 src/main.ts                                   |  1 +
 4 files changed, 136 insertions(+)
 create mode 100644 src/codemods/__snapshots__/exponentiation.test.ts.snap
 create mode 100644 src/codemods/exponentiation.test.ts
 create mode 100644 src/codemods/exponentiation.ts

diff --git a/src/codemods/__snapshots__/exponentiation.test.ts.snap b/src/codemods/__snapshots__/exponentiation.test.ts.snap
new file mode 100644
index 0000000..c26d3b8
--- /dev/null
+++ b/src/codemods/__snapshots__/exponentiation.test.ts.snap
@@ -0,0 +1,27 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`exponentiation > should handle Math.pow in expressions 1`] = `
+"const result = (a + b) ** (c - d) * 2;
+      const value = 10 + (x) ** (y);
+    "
+`;
+
+exports[`exponentiation > should handle nested Math.pow calls 1`] = `
+"const result = ((2) ** (3)) ** (4);
+    "
+`;
+
+exports[`exponentiation > should not change code without Math.pow 1`] = `
+"
+      const result = x ** y;
+      const squared = 2 ** 3;
+      const value = Math.sqrt(4);
+    "
+`;
+
+exports[`exponentiation > should replace Math.pow with exponentiation operator 1`] = `
+"const result = (2) ** (3);
+      const squared = (x) ** (2);
+      const complex = (base) ** (exponent);
+    "
+`;
diff --git a/src/codemods/exponentiation.test.ts b/src/codemods/exponentiation.test.ts
new file mode 100644
index 0000000..98818b9
--- /dev/null
+++ b/src/codemods/exponentiation.test.ts
@@ -0,0 +1,57 @@
+import {describe, it, expect} from 'vitest';
+import {codemod} from './exponentiation.js';
+
+describe('exponentiation', () => {
+  it('should replace Math.pow with exponentiation operator', () => {
+    const source = `
+      const result = Math.pow(2, 3);
+      const squared = Math.pow(x, 2);
+      const complex = Math.pow(base, exponent);
+    `;
+    const result = codemod.apply({source});
+    expect(result).toMatchSnapshot();
+  });
+
+  it('should handle nested Math.pow calls', () => {
+    const source = `
+      const result = Math.pow(Math.pow(2, 3), 4);
+    `;
+    const result = codemod.apply({source});
+    expect(result).toMatchSnapshot();
+  });
+
+  it('should handle Math.pow in expressions', () => {
+    const source = `
+      const result = Math.pow(a + b, c - d) * 2;
+      const value = 10 + Math.pow(x, y);
+    `;
+    const result = codemod.apply({source});
+    expect(result).toMatchSnapshot();
+  });
+
+  it('should not change code without Math.pow', () => {
+    const source = `
+      const result = x ** y;
+      const squared = 2 ** 3;
+      const value = Math.sqrt(4);
+    `;
+    const result = codemod.apply({source});
+    expect(result).toMatchSnapshot();
+  });
+
+  describe('test', () => {
+    it('should detect Math.pow usage', () => {
+      const source = `
+        const result = Math.pow(2, 3);
+      `;
+      expect(codemod.test({source})).toBe(true);
+    });
+
+    it('should not detect when there is no Math.pow', () => {
+      const source = `
+        const result = x ** y;
+      `;
+      expect(codemod.test({source})).toBe(false);
+    });
+  });
+});
diff --git a/src/codemods/exponentiation.ts b/src/codemods/exponentiation.ts
new file mode 100644
index 0000000..755fb31
--- /dev/null
+++ b/src/codemods/exponentiation.ts
@@ -0,0 +1,51 @@
+import {parse, Lang, type Edit, type NapiConfig} from '@ast-grep/napi';
+import type {Options, CodeMod} from '../shared.js';
+
+const mathPowRule: NapiConfig = {
+  rule: {
+    pattern: 'Math.pow($BASE, $EXPONENT)'
+  }
+};
+
+export const codemod: CodeMod = {
+  test(options: Options): boolean {
+    const ast = parse(Lang.TypeScript, options.source);
+    const root = ast.root();
+
+    return root.has(mathPowRule);
+  },
+  apply(options: Options): string {
+    let source = options.source;
+
+    while (true) {
+      const ast = parse(Lang.TypeScript, source);
+      const root = ast.root();
+
+      const mathPowCalls = root.findAll(mathPowRule);
+      if (mathPowCalls.length === 0) {
+        break;
+      }
+
+      const edits: Edit[] = [];
+
+      for (const node of mathPowCalls) {
+        const base = node.getMatch('BASE');
+        const exponent = node.getMatch('EXPONENT');
+        if (base && exponent) {
+          const baseText = base.text();
+          const exponentText = exponent.text();
+          const edit = node.replace(`(${baseText}) ** (${exponentText})`);
+          edits.push(edit);
+        }
+      }
+
+      const newSource = root.commitEdits(edits);
+      if (newSource === source) {
+        break;
+      }
+      source = newSource;
+    }
+
+    return source;
+  }
+};
diff --git a/src/main.ts b/src/main.ts
index b70bf3a..ed54c29 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -4,6 +4,7 @@ export {codemod as arrayIncludes} from './codemods/array-includes.js';
 export {codemod as arrayToReversed} from './codemods/array-to-reversed.js';
 export {codemod as arrayToSorted} from './codemods/array-to-sorted.js';
 export {codemod as arrayToSpliced} from './codemods/array-to-spliced.js';
+export {codemod as exponentiation} from './codemods/exponentiation.js';
 export {codemod as nullishCoalescing} from './codemods/nullish-coalescing.js';
 export {codemod as postcssSignFunctions} from './codemods/postcss-sign-functions.js';
 export {codemod as stringIncludes} from './codemods/string-includes.js';