Make moment optional from our UMD builds (chartjs#5978)

docs/getting-started/integration.md

@@ -11,26 +11,76 @@ Chart.js can be integrated with plain JavaScript or with different module loader
 </script>
 ```
 
-## Webpack
+## Common JS
 
 ```javascript
-import Chart from 'chart.js';
+var Chart = require('chart.js');
 var myChart = new Chart(ctx, {...});
 ```
 
-## Common JS
+## Bundlers (Webpack, Rollup, etc.)
 
 ```javascript
-var Chart = require('chart.js');
+import Chart from 'chart.js';
 var myChart = new Chart(ctx, {...});
 ```
 
+**Note:** Moment.js is installed along Chart.js as dependency. If you don't want to use Momemt.js (either because you use a different date adapter or simply because don't need time functionalities), you will have to configure your bundler to exclude this dependency (e.g. using [`externals` for Webpack](https://webpack.js.org/configuration/externals/) or [`external` for Rollup](https://rollupjs.org/guide/en#peer-dependencies)).
+
+```javascript
+// Webpack
+{
+    externals: {
+        moment: 'moment'
+    }
+}
+```
+
+```javascript
+// Rollup
+{
+    external: {
+        ['moment']
+    }
+}
+```
+
 ## Require JS
 
+**Important:** RequireJS [can **not** load CommonJS module as is](https://requirejs.org/docs/commonjs.html#intro), so be sure to require one of the UMD builds instead (i.e. `dist/Chart.js`, `dist/Chart.min.js`, etc.).
+
 ```javascript
-require(['path/to/chartjs/dist/Chart.js'], function(Chart) {
+require(['path/to/chartjs/dist/Chart.min.js'], function(Chart){
     var myChart = new Chart(ctx, {...});
 });
 ```
 
-> **Important:** RequireJS [can **not** load CommonJS module as is](https://requirejs.org/docs/commonjs.html#intro), so be sure to require one of the built UMD files instead (i.e. `dist/Chart.js`, `dist/Chart.min.js`, etc.).
+**Note:** starting v2.8, Moment.js is an optional dependency for `Chart.js` and `Chart.min.js`. In order to use the time scale with Moment.js, you need to make sure Moment.js is fully loaded **before** requiring Chart.js. You can either use a shim:
+
+```javascript
+require.config({
+    shim: {
+        'chartjs': {
+            deps: ['moment']    // enforce moment to be loaded before chartjs
+        }
+    },
+    paths: {
+        'chartjs': 'path/to/chartjs/dist/Chart.min.js',
+        'moment': 'path/to/moment'
+    }
+});
+
+require(['chartjs'], function(Chart) {
+    new Chart(ctx, {...});
+});
+```
+
+or simply use two nested `require()`:
+
+```javascript
+require(['moment'], function() {
+    require(['chartjs'], function(Chart) {
+        new Chart(ctx, {...});
+    });
+});
+```

package.json

@@ -6,7 +6,7 @@
   "license": "MIT",
   "jsdelivr": "dist/Chart.min.js",
   "unpkg": "dist/Chart.min.js",
-  "main": "src/chart.js",
+  "main": "dist/Chart.js",
   "keywords": [
     "canvas",
     "charts",

rollup.config.js

@@ -3,6 +3,7 @@
 const commonjs = require('rollup-plugin-commonjs');
 const resolve = require('rollup-plugin-node-resolve');
 const terser = require('rollup-plugin-terser').terser;
+const optional = require('./rollup.plugins').optional;
 const pkg = require('./package.json');
 
 const input = 'src/chart.js';
@@ -21,7 +22,10 @@ module.exports = [
 		input: input,
 		plugins: [
 			resolve(),
-			commonjs()
+			commonjs(),
+			optional({
+				include: ['moment']
+			})
 		],
 		output: {
 			name: 'Chart',
@@ -42,6 +46,9 @@ module.exports = [
 		plugins: [
 			resolve(),
 			commonjs(),
+			optional({
+				include: ['moment']
+			}),
 			terser({
 				output: {
 					preamble: banner

rollup.plugins.js

@@ -0,0 +1,61 @@
+/* eslint-env es6 */
+
+const UMD_WRAPPER_RE = /(\(function \(global, factory\) \{)((?:\s.*?)*)(\}\(this,)/;
+const CJS_FACTORY_RE = /(module.exports = )(factory\(.*?\))( :)/;
+const AMD_FACTORY_RE = /(define\()(.*?, factory)(\) :)/;
+
+function optional(config = {}) {
+	return {
+		name: 'optional',
+		renderChunk(code, chunk, options) {
+			if (options.format !== 'umd') {
+				this.error('only UMD format is currently supported');
+			}
+
+			const wrapper = UMD_WRAPPER_RE.exec(code);
+			const include = config.include;
+			if (!wrapper) {
+				this.error('failed to parse the UMD wrapper');
+			}
+
+			let content = wrapper[2];
+			let factory = (CJS_FACTORY_RE.exec(content) || [])[2];
+			let updated = false;
+
+			for (let lib of chunk.imports) {
+				if (!include || include.indexOf(lib) !== -1) {
+					const regex = new RegExp(`require\\('${lib}'\\)`);
+					if (!regex.test(factory)) {
+						this.error(`failed to parse the CJS require for ${lib}`);
+					}
+
+					// We need to write inline try / catch with explicit require
+					// in order to enable statical extraction of dependencies:
+					// try { return require('moment'); } catch(e) {}
+					const loader = `function() { try { return require('${lib}'); } catch(e) { } }()`;
+					factory = factory.replace(regex, loader);
+					updated = true;
+				}
+			}
+
+			if (!updated) {
+				return;
+			}
+
+			// Replace the CJS factory by our updated one.
+			content = content.replace(CJS_FACTORY_RE, `$1${factory}$3`);
+
+			// Replace the AMD factory by our updated one: we need to use the
+			// following AMD form in order to be able to try/catch require:
+			// define(['require'], function(require) { ... require(...); ... })
+			// https://github.com/amdjs/amdjs-api/wiki/AMD#using-require-and-exports
+			content = content.replace(AMD_FACTORY_RE, `$1['require'], function(require) { return ${factory}; }$3`);
+
+			return code.replace(UMD_WRAPPER_RE, `$1${content}$3`);
+		}
+	};
+}
+
+module.exports = {
+	optional
+};