roughike / indent

Change indentation in multiline Dart strings while preserving the existing relative indentation. Kotlin's trimIndent and trimMargin for Dart.

indent

Change indentation in multiline Dart strings while preserving the existing relative indentation.

A GIF speaks more than a thousand words:

You can run the example app yourself by running cd example && pub get && webdev serve from the project root.

Usage

For convenience, the library adds the following extension members on Dart's String class.

You can also wrap a string with the Indentation class and call methods on that - this is what the extension methods do under the hood.

unindent()

If you found this library from a Google search, you're probably looking for the unindent() method. It's the use case this library was originally created for.

For example, this:

import 'package:indent/indent.dart';

print('''
          Hello
        there
             World!
'''.unindent());

outputs this:

  Hello
there
     World!

It gets rid of the common indentation while preserving the relative indentation. This is like Kotlin's trimIndent() or Java 12's align().

trimMargin([String marginPrefix = '|'])

Trims the leading whitespace followed by the marginPrefix from each line.

For example, this:

import 'package:indent/indent.dart';

print('''
        |  Hello
        |there
        |    World!
'''.trimMargin());

outputs this:

  Hello
there
    World!

Behaves just like trimMargin in Kotlin.

indent(int indentationLevel)

Indents a string with the desired indentation level while preserving relative indentation.

For example, this:

import 'package:indent/indent.dart';

print('''
   Hello
World
'''.indent(2));

prints:

     Hello
  World

If the starting indentation level is higher than the desired one, the value will be unindented accordingly.

This:

import 'package:indent/indent.dart';

print('''
          Hello
       World
'''.indent(2));

also prints:

     Hello
  World

(calling indent(0) is equal to calling unindent().)

indentBy(int howMuch)

Changes the indentation level in a string by howMuch.

A positive value for howMuch adds indentation.

For example, this:

import 'package:indent/indent.dart';

print('''
   Hello
World
'''.indentBy(4));

prints this:

       Hello
    World

When a negative value for howMuch is given, indentation is removed accordingly.

This:

import 'package:indent/indent.dart';

print('''
       Hello
    World
'''.indentBy(-4));

prints this:

   Hello
World

getIndentationLevel()

Returns the common indentation level in a string.

For example, this:

import 'package:indent/indent.dart';

final int indentationLevel= '''
     Hello
  World
'''.getIndentationLevel();

returns 2 as the two spaces before World is the lowest common indentation in the string.

indent's Issues

Problem when used with inlined variables

For example:

String test() {
    String t = '123123\n123123';
    return '''
      _FutureBuilderError{
        error: Instance of 'WhatIfGodSmokedCannabisError', 
        stackTrace: 
          $t
      }
    '''.unindent();
}

Returns:

        _FutureBuilderError{
        error: Instance of 'WhatIfGodSmokedCannabisError, 
        stackTrace: 
          123123
123123
      }

Desirable behaviour

To (optionally?) put proper amount of tabs/spaces before each new line of inlined variable.

`unindent` incorrectly adds an additional newline

void main() {
  final foo = '''
  test
  ''';
  final bar = '''
  test
  '''.unindent();
}