Add test for Node ESM conditional exports

Author: vikerman

.github/workflows/test.yml

@@ -7,15 +7,19 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
+        # Change the condition for ESM Dist Test below when changing this.
         node-version: [10.x, 12.x, 14.x]
     steps:
-    - name: Checkout
-      uses: actions/checkout@v2
-    - name: Use Node.js ${{ matrix.node-version }}
-      uses: actions/setup-node@v1
-      with:
-        node-version: ${{ matrix.node-version }}
-    - name: Install
-      run: npm install
-    - name: Build and Test
-      run: npm test
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Use Node.js ${{ matrix.node-version }}
+        uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node-version }}
+      - name: Install
+        run: npm install
+      - name: Build and Test
+        run: npm test
+      - if: matrix.node-version == '14.x'
+        name: ESM Dist Test
+        run: npm run test:dist

.gitignore

@@ -5,3 +5,4 @@ package-lock.json
 dist
 mini
 yarn.lock
+htm.tgz

package.json

@@ -48,8 +48,9 @@
     "build:babel": "cd packages/babel-plugin-htm && npm run build",
     "build:babel-transform-jsx": "cd packages/babel-plugin-transform-jsx-to-htm && npm run build",
     "build:mjsalias": "cp dist/htm.module.js dist/htm.mjs && cp mini/index.module.js mini/index.mjs && cp preact/index.module.js preact/index.mjs && cp preact/standalone.module.js preact/standalone.mjs && cp react/index.module.js react/index.mjs",
-    "test": "eslint src/**/*.mjs test/**/*.mjs && npm run build && jest test",
+    "test": "eslint src/**/*.mjs test/**/*.mjs --ignore-path .gitignore && npm run build && jest test",
     "test:perf": "v8 test/__perftest.mjs",
+    "test:dist": "npm pack && mv htm*.tgz test/fixtures/esm/htm.tgz && cd test/fixtures/esm && npm install && node index.js",
     "release": "npm t && git commit -am \"$npm_package_version\" && git tag $npm_package_version && git push && git push --tags && npm publish"
   },
   "files": [

test/fixtures/esm/index.js

@@ -0,0 +1,5 @@
+import "htm";
+import "htm/preact";
+import "htm/preact/standalone";
+// TODOD: Enable once react distro is ESM compatible.
+// import "htm/react";

test/fixtures/esm/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "htm_dist_test",
+  "type": "module",
+  "private": true,
+  "description": "A package to test importing htm as ES modules in Node",
+  "dependencies": {
+    "htm": "file:htm.tgz",
+    "preact": "^10.4.1"
+  }
+}