feat!: add optional --main for build to include "main" (mikeal#8)

Don't include "main" in package.json by default, but include it if --main is
passed.

Author: rvagg

src/build.js

@@ -25,6 +25,9 @@ const run = async opts => {
   pkg.dist = dist
   return pkg
 }
-run.schema = { tests: false }
+run.schema = {
+  tests: false,
+  main: false
+}
 
 export default run

src/package/index.js

@@ -18,13 +18,14 @@ const { writeFile, mkdir, unlink, readdir, readFile, copyFile } = fs
 const plugins = [preserveShebangs.preserveShebangs()]
 
 class Package {
-  constructor ({ cwd, hooks, tests }) {
+  constructor ({ cwd, hooks, tests, main }) {
     this.cwd = cwd
     this.hooks = hooks || {}
     this.parsed = this.parse()
     this.files = new Map()
     this.testFiles = new Map()
     this.includeTests = tests
+    this.includeMain = main
   }
 
   file (url) {
@@ -181,7 +182,11 @@ class Package {
     const json = copy(this.pkgjson)
 
     delete json.type
-    json.main = `./${join('./cjs', json.main || './index.js')}`
+    if (this.includeMain) {
+      json.main = `./${join('./cjs', json.main || './index.js')}`
+    } else {
+      delete json.main
+    }
     json.browser = {}
     json.exports = {}
     const _join = (...args) => './' + join(...args)

test/fixtures/pkg-kitchensink/output-main/cjs/src/browser.js

@@ -0,0 +1,11 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+var sub = require('./sub.js');
+var browser = require('./sub/browser.js');
+
+
+
+exports.mod = sub;
+exports.sub = browser;

test/fixtures/pkg-kitchensink/output-main/cjs/src/deno.js

@@ -0,0 +1,11 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+var sub = require('./sub.js');
+var index = require('./sub/index.js');
+
+
+
+exports.mod = sub;
+exports.sub = index;

test/fixtures/pkg-kitchensink/output-main/cjs/src/index.js

@@ -0,0 +1,11 @@
+'use strict';
+
+Object.defineProperty(exports, '__esModule', { value: true });
+
+var sub = require('./sub.js');
+var index = require('./sub/index.js');
+
+
+
+exports.mod = sub;
+exports.sub = index;

test/fixtures/pkg-kitchensink/output-main/cjs/src/secondary.js

@@ -0,0 +1,5 @@
+'use strict';
+
+var secondary = 'secondary';
+
+module.exports = secondary;

test/fixtures/pkg-kitchensink/output-main/cjs/src/sub.js

@@ -0,0 +1,5 @@
+'use strict';
+
+var sub = 'sub';
+
+module.exports = sub;

test/fixtures/pkg-kitchensink/output-main/cjs/src/sub/browser.js

@@ -0,0 +1,5 @@
+'use strict';
+
+var browser = 'browser';
+
+module.exports = browser;

test/fixtures/pkg-kitchensink/output-main/cjs/src/sub/index.js

@@ -0,0 +1,5 @@
+'use strict';
+
+var index = 'import';
+
+module.exports = index;

test/fixtures/pkg-kitchensink/output-main/esm/package.json

@@ -0,0 +1 @@
+{ "type" : "module" }