From 40651613e9281809f508178cd778eac85d4654a5 Mon Sep 17 00:00:00 2001
From: Joe Hildebrand <joe-github@cursive.net>
Date: Mon, 26 Feb 2024 08:28:27 -0700
Subject: [PATCH] Half-support node 18

---
 .github/workflows/node.js.yml |  2 +-
 README.md                     |  9 ++++---
 package.json                  |  2 +-
 test/index.test.js            | 47 +++++++++++++++++++++--------------
 4 files changed, 35 insertions(+), 25 deletions(-)

diff --git a/.github/workflows/node.js.yml b/.github/workflows/node.js.yml
index 7c4fec5..6b4fe66 100644
--- a/.github/workflows/node.js.yml
+++ b/.github/workflows/node.js.yml
@@ -12,7 +12,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [20.x, 21.x]
+        node-version: [18.x, 20.x, 21.x]
         os: [ubuntu-latest, windows-latest, macos-latest]
 
     runs-on: ${{ matrix.os }}
diff --git a/README.md b/README.md
index 26b87fe..9c9d7d2 100644
--- a/README.md
+++ b/README.md
@@ -81,11 +81,12 @@ export type FromMemOptions = {
 
 ## Caveats
 
-- This module has a strong requirement for node 20.8+ at runtime, due to a bug
-that crashes node in node's vm module that got fixed there and in 21.0.
+- This module has a strong requirement for node 20.8+ at runtime when using
+  the es6 format, due to a bug that crashes node in node's vm module that got
+  fixed there and in 21.0.  There is a runtime check to prevent the crash.
 - This module requires being run with the `--experimental-vm-modules` flag
-for node for the moment.  Hopefully, we will track changes to the API as they
-happen.
+  for node for the moment.  Hopefully, we will track changes to the API as
+  they happen.
 
 [![Tests](https://github.com/peggyjs/from-mem/actions/workflows/node.js.yml/badge.svg)](https://github.com/peggyjs/from-mem/actions/workflows/node.js.yml)
 [![codecov](https://codecov.io/gh/peggyjs/from-mem/graph/badge.svg?token=CWQ7GSH0ZI)](https://codecov.io/gh/peggyjs/from-mem)
diff --git a/package.json b/package.json
index d699538..bd41a24 100644
--- a/package.json
+++ b/package.json
@@ -29,6 +29,6 @@
   },
   "packageManager": "pnpm@8.15.4",
   "engines": {
-    "node": ">=20.8"
+    "node": ">=18"
   }
 }
diff --git a/test/index.test.js b/test/index.test.js
index 384538e..4f52058 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -4,9 +4,12 @@ const assert = require("node:assert");
 const fromMem = require("../index.js");
 const { join, parse } = require("node:path");
 const { pathToFileURL } = require("node:url");
+const semver = require("semver");
 const test = require("node:test");
 const vm = require("node:vm");
 
+const is20 = semver.satisfies(process.version, ">=20.8");
+
 test("options", async() => {
   assert.equal(typeof fromMem, "function");
   await assert.rejects(() => fromMem(""), /filename is required/);
@@ -69,24 +72,26 @@ test("guess", async() => {
   });
   assert.equal(cjs3, 4);
 
-  const mjs = await fromMem("export default 4", {
-    filename: join(__dirname, "test_guess3.mjs"),
-    format: "guess",
-  });
-  assert.equal(mjs.default, 4);
-
-  const mjs2 = await fromMem("export default 4", {
-    filename: join(__dirname, "fixtures", "mjs", "test_guess4.js"),
-    format: "guess",
-  });
-  assert.equal(mjs2.default, 4);
-
-  // Hit the cache
-  const mjs3 = await fromMem("export default 4", {
-    filename: join(__dirname, "fixtures", "mjs", "test_guess4.js"),
-    format: "guess",
-  });
-  assert.equal(mjs3.default, 4);
+  if (is20) {
+    const mjs = await fromMem("export default 4", {
+      filename: join(__dirname, "test_guess3.mjs"),
+      format: "guess",
+    });
+    assert.equal(mjs.default, 4);
+
+    const mjs2 = await fromMem("export default 4", {
+      filename: join(__dirname, "fixtures", "mjs", "test_guess4.js"),
+      format: "guess",
+    });
+    assert.equal(mjs2.default, 4);
+
+    // Hit the cache
+    const mjs3 = await fromMem("export default 4", {
+      filename: join(__dirname, "fixtures", "mjs", "test_guess4.js"),
+      format: "guess",
+    });
+    assert.equal(mjs3.default, 4);
+  }
 
   await assert.rejects(() => fromMem("export default 4", {
     filename: join(__dirname, "fixtures", "bad", "test_guess5.js"),
@@ -96,7 +101,11 @@ test("guess", async() => {
   fromMem.guessModuleType.clearCache();
 });
 
-test("esm", async() => {
+test("esm", async t => {
+  if (!is20) {
+    t.skip(`Skipping esm tests on ${process.version}`);
+    return;
+  }
   const mjs4 = await fromMem("export default 5", {
     filename: join(__dirname, "test4.js"),
     format: "es",