* Add documentation

cli/run/stdin.ts

@@ -22,10 +22,6 @@ export function stdinPlugin(): Plugin {
 
 function readStdin(): Promise<string> {
 	return new Promise((resolve, reject) => {
-		if (typeof process == 'undefined' || typeof process.stdin == 'undefined') {
-			return reject(new Error('stdin input is invalid in browser'));
-		}
-
 		const chunks: Buffer[] = [];
 		process.stdin.setEncoding('utf8');
 		process.stdin

docs/01-command-line-reference.md

@@ -253,6 +253,7 @@ Many options have command line equivalents. In those cases, any arguments passed
 --silent                    Don't print warnings
 --sourcemapExcludeSources   Do not include source code in source maps
 --sourcemapFile <file>      Specify bundle position for source maps
+--stdin                     read input from stdin
 --strictDeprecations        Throw errors for deprecated features
 --no-treeshake              Disable tree-shaking optimisations
 --no-treeshake.annotations  Ignore pure call annotations
@@ -306,3 +307,29 @@ npm run build -- --environment BUILD:development
 ```
 
 then the config file will receive `process.env.INCLUDE_DEPS === 'true'` and `process.env.BUILD === 'development'`.
+
+#### `--stdin`
+
+Read input from `stdin` instead of a file. This is the default when no config file is used and no entry point is provided and allows piping content to Rollup. When using a config file, this will replace `input` with what is read from `stdin`. See also [Reading a file from stdin](guide/en/#reading-a-file-from-stdin).
+
+#### `--no-stdin`
+
+Do not read input from `stdin`. Setting this flag will also make sure Rollup interprets `-` as a regular file name instead of interpreting this as the name of `stdin`. See also [Reading a file from stdin](guide/en/#reading-a-file-from-stdin).
+
+### Reading a file from stdin
+
+When using the command line interface, Rollup can also read content from stdin:
+
+```
+echo "export const foo = 42;" | rollup --format cjs --file out.js
+```
+
+When this file contains imports, Rollup will try to resolve them relative to the current working directory. When a config file is used, Rollup will only use `stdin` as an entry point if either the entry point is called `-` or you pass the [`--stdin`](guide/en/#--stdin) flag. To read a non-entry-point file from stdin, just call it `-`, which is the file name that is used internally to reference `stdin`. I.e.
+
+```js
+import foo from "-";
+```
+
+in any file will prompt Rollup to try to read the imported file from `stdin`. You can pass the [`--no-stdin`](guide/en/#--no-stdin) CLI flag to Rollup to treat `-` as a regular file name instead.
+
+The JavaScript API will always treat `-` as a regular file name.