Remove jsnext:main

The field is deprecated and replaced with package.module. Additionally it caused many issues with packages that used it incorrectly. Fixes #844, #1037, #1048, #1062.

src/Resolver.js

@@ -268,15 +268,11 @@ class Resolver {
 
   getPackageMain(pkg) {
     // libraries like d3.js specifies node.js specific files in the "main" which breaks the build
-    // we use the "module" or "jsnext:main" field to get the full dependency tree if available.
+    // we use the "module" or "browser" field to get the full dependency tree if available.
     // If this is a linked module with a `source` field, use that as the entry point.
-    let main = [
-      pkg.source,
-      pkg.module,
-      pkg['jsnext:main'],
-      pkg.browser,
-      pkg.main
-    ].find(entry => typeof entry === 'string');
+    let main = [pkg.source, pkg.module, pkg.browser, pkg.main].find(
+      entry => typeof entry === 'string'
+    );
 
     // Default to index file if no main field find
     if (!main || main === '.' || main === './') {

test/javascript.js

@@ -542,28 +542,7 @@ describe('javascript', function() {
     assert.equal(output.test(), 'pkg-es6-module');
   });
 
-  it('should resolve the jsnext:main field before main', async function() {
-    let b = await bundle(
-      __dirname + '/integration/resolve-entries/jsnext-field.js'
-    );
-
-    assertBundleTree(b, {
-      name: 'jsnext-field.js',
-      assets: ['jsnext-field.js', 'jsnext.module.js'],
-      childBundles: [
-        {
-          type: 'map'
-        }
-      ]
-    });
-
-    let output = run(b);
-
-    assert.equal(typeof output.test, 'function');
-    assert.equal(output.test(), 'pkg-jsnext-module');
-  });
-
-  it('should resolve the module field before jsnext:main', async function() {
+  it('should resolve the module field before main', async function() {
     let b = await bundle(
       __dirname + '/integration/resolve-entries/both-fields.js'
     );