Add --simulate to show which files would change to close #710

src/cli.ts

@@ -233,6 +233,13 @@ const yargs = require('yargs')
 	.describe('b', 'Keep a backup file of the original content.')
 	.alias('b', 'keep-backup')
 
+	.boolean('S')
+	.describe(
+		'S',
+		'Do everything but write the files. The names of the files that would be changed are printed as usual, and no backup is made.'
+	)
+	.alias('S', 'simulate')
+
 	.boolean('m')
 	.describe(
 		'm',
@@ -384,7 +391,7 @@ All variables, except from module, date objects, \`nl\` and \`_\`, has a corresp
 
 Upper Case Free	Lower Case Free
 	a
-C	c
+C	
 D	
 F	
 	g
@@ -403,10 +410,10 @@ Z	z
 
 
     */
-	.boolean('S')
-	.alias('S', 'status-compact')
+	.boolean('c')
+	.alias('c', 'status-compact')
 	.describe(
-		'S',
+		'c',
 		'As the last thing before ending any execution a status report will be printed as one line of JSON. Will print even in combination with `--quiet-total`. Will incude extra info about the inner workings of the engine in combination with the `--verbose` flag.'
 	)
 

src/engine.ts

@@ -212,6 +212,11 @@ function doReplacement(_file_rr: string, _config_rr: any, _data_rr: string) {
 		return;
 	}
 
+	// --simulate does everything but write, so the file is named as if it was changed
+	if (_config_rr.simulate) {
+		return updated(_file_rr, _config_rr);
+	}
+
 	// Release the memory while storing files
 	_data_rr = '';
 

test/cli/run.sh

@@ -451,6 +451,13 @@ assert		 		"rexreplace 'b' 'x' my.file --content-delimiter '\x4' 2>&1 | grep -c
 assert		 		"rexreplace 'b' 'x' my.file --delimiter '\x4' 2>&1 | grep -c 'Invalid escape sequence in --delimiter'"    '1'
 assert		 		"cat my.file"    'foobar'
 
+# --simulate: the files that would be changed are named, but nothing is written (#710)
+reset
+assert		 		"rexreplace 'oo' 'x' my.file your.file --simulate"    'my.file'
+assert		 		"cat my.file"    'foobar'
+assert		 		"rexreplace 'b' 'x' my.file -S"    'my.file'
+assert		 		"cat my.file"    'foobar'
+
 # --full-path
 reset
 assert		 		"rexreplace 'b' 'x' my.file -f"    "$(pwd -P)/my.file"

test/js/fix/710.test.js

@@ -0,0 +1,55 @@
+// https://github.com/mathiasrw/rexreplace/issues/710
+// There was no way to see which files a command would change without changing them.
+import {describe, test, expect} from 'bun:test';
+import fs from 'fs';
+import {rr, rrStatus} from '../helper.js';
+
+// Note that rr() from the helper sets voidAsync per default, so the async flow is `voidAsync: false`
+const flows = [
+	['the async flow', {voidAsync: false}],
+	['--void-async', {voidAsync: true}],
+];
+
+// Make a.file and c.file with `foo`, and b.file with `bar` (nothing to replace)
+function makeFiles() {
+	fs.writeFileSync('a.file', 'foo');
+	fs.writeFileSync('b.file', 'bar');
+	fs.writeFileSync('c.file', 'foo');
+	return {includeGlob: ['*.file'], simulate: true};
+}
+
+const contents = () => ['a.file', 'b.file', 'c.file'].map(name => fs.readFileSync(name, 'utf8'));
+
+describe('#710 --simulate', () => {
+	test.each(flows)(
+		'names the files that would be changed, and changes nothing, with %s',
+		async (name, flags) => {
+			const result = await rr('o', 'x', {...makeFiles(), ...flags});
+			expect(result.out.split('\n').sort()).toEqual(['', 'a.file', 'c.file']);
+			expect(result.err).toBe('');
+			expect(result.exit).toBe(null);
+			expect(contents()).toEqual(['foo', 'bar', 'foo']);
+			expect(fs.readdirSync('.').sort()).toEqual(['a.file', 'b.file', 'c.file']);
+		}
+	);
+
+	test('makes no backup, also with --keep-backup', async () => {
+		await rr('o', 'x', {...makeFiles(), keepBackup: true});
+		expect(fs.readdirSync('.').sort()).toEqual(['a.file', 'b.file', 'c.file']);
+	});
+
+	test('has the files that would be changed in the status report', async () => {
+		const status = await rrStatus('o', 'x', makeFiles());
+		expect(status.files).toEqual({
+			searched: ['a.file', 'b.file', 'c.file'],
+			updated: ['a.file', 'c.file'],
+		});
+	});
+
+	test('with --name-all names all files, but only the changed ones are updated', async () => {
+		const config = {...makeFiles(), nameAll: true};
+		expect((await rr('o', 'x', config)).out).toBe('a.file\nb.file\nc.file\n');
+		expect((await rrStatus('o', 'x', config)).files.updated).toEqual(['a.file', 'c.file']);
+		expect(contents()).toEqual(['foo', 'bar', 'foo']);
+	});
+});

test/js/fix/742.test.js

@@ -210,7 +210,7 @@ describe('#742 the CLI', () => {
 		});
 	});
 
-	test.each(['--status-compact', '-S'])(
+	test.each(['--status-compact', '-c'])(
 		'%s prints the status report on one line, with no line break in front',
 		flag => {
 			fs.writeFileSync('a.file', 'foo');