Merge pull request #1 from roughike/trim-margin

v1.1.0

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.1.0
+
+* Adds `trimMargin()` method that behaves like Kotlin's trimMargin.
+
 ## 1.0.0+2
 
 * "performance improvements" - replace `List.generate(indentationLevel)` with a `StringBuffer` and a for loop. Nobody will probably notice the difference, but go ahead and enjoy the performance improvement of a couple Planck times anyway.

README.md

@@ -45,6 +45,32 @@ there
 
 It gets rid of the common indentation while preserving the relative indentation. This is like [Kotlin's trimIndent()](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/trim-indent.html) or Java 12's `align()`.
 
+### trimMargin([String marginPrefix = '|'])
+
+Trims the leading whitespace followed by the `marginPrefix` from each line.
+
+For example, this:
+
+```dart
+import 'package:indent/indent.dart';
+
+print('''
+        |  Hello
+        |there
+        |    World!
+'''.trimMargin());
+```
+
+outputs this:
+
+```
+  Hello
+there
+    World!
+```
+
+Behaves just like [trimMargin in Kotlin](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/trim-margin.html).
+
 ### indent(int indentationLevel)
 
 Indents a string with the desired indentation level while preserving relative indentation.

analysis_options.yaml

@@ -1,14 +1 @@
-# Defines a default set of lint rules enforced for
-# projects at Google. For details and rationale,
-# see https://github.com/dart-lang/pedantic#enabled-lints.
-include: package:pedantic/analysis_options.yaml
-
-# For lint rules and documentation, see http://dart-lang.github.io/linter/lints.
-# Uncomment to specify additional rules.
-# linter:
-#   rules:
-#     - camel_case_types
-
-analyzer:
-#   exclude:
-#     - path/to/excluded/files/**
+include: package:lint/analysis_options_package.yaml

example/web/index.html

@@ -8,6 +8,7 @@
     <button id="increase">indentBy(1)</button>
     <button id="strip-extra-indent">unindent()</button>
     <button id="with-ten-indentation">indent(10)</button>
+    <button id="trim-margin">trimMargin('|')</button>
 </div>
 <p>getIndentationLevel(): <strong id="indentation-level">--</strong></p>
 <br/>

example/web/main.dart

@@ -24,6 +24,10 @@ void main() {
   document.getElementById('with-ten-indentation').onClick.listen((_) {
     text.value = text.value.indent(10);
   });
+
+  document.getElementById('trim-margin').onClick.listen((_) {
+    text.value = text.value.trimMargin('|');
+  });
 }
 
 void _startMonitoringIndentationLevel(TextAreaElement text) {

lib/src/indentation.dart

@@ -1,16 +1,14 @@
 import 'dart:convert';
 
-import 'package:indent/indent.dart';
-
 /// Change indentation in a [String] while preserving existing relative
 /// indentation.
 ///
 /// For easier usage, see [IndentedString] in string_extensions.dart.
 class Indentation {
-  const Indentation(this._value);
-  final String _value;
+  const Indentation(this._input);
+  final String _input;
 
-  /// Returns the indentation level of [_value].
+  /// Returns the indentation level of [_input].
   ///
   /// An indentation level is determined by finding a non-empty line with the
   /// least amount of leading whitespace.
@@ -27,7 +25,7 @@ class Indentation {
     return _findCommonIndentationLevel(lines);
   }
 
-  /// Returns [_value] with all extra indentation stripped while preserving
+  /// Returns [_input] with all extra indentation stripped while preserving
   /// relative indentation.
   ///
   /// For example, the input:
@@ -45,7 +43,7 @@ class Indentation {
   /// Calling [unindent] is equivalent of calling [indent] with the value of 0.
   String unindent() => indent(0);
 
-  /// Returns [_value] with [indentationLevel] applied while preserving relative
+  /// Returns [_input] with [indentationLevel] applied while preserving relative
   /// indentation.
   ///
   /// For example, the input:
@@ -76,7 +74,7 @@ class Indentation {
     return _indent(lines, currentIndentationLevel, indentationLevel);
   }
 
-  /// Returns [_value] with indentation level changed by [howMuch].
+  /// Returns [_input] with indentation level changed by [howMuch].
   ///
   /// For example, the input:
   ///
@@ -109,16 +107,67 @@ class Indentation {
     );
   }
 
+  /// Returns [_input], but trims leading whitespace characters followed by the
+  /// given [marginPrefix] from each line.
+  ///
+  /// Also removes the first and last lines if they are blank, i.e. they only
+  /// contain whitespace characters.
+  ///
+  /// For example, given that the [marginPrefix] is "|" (the default), the input:
+  ///
+  ///       |   Hello
+  ///       | there
+  ///       |    World
+  ///
+  /// will become:
+  ///
+  ///    Hello
+  ///  there
+  ///     World
+  ///
+  /// Leaves lines that don't contain [marginPrefix] untouched.
+  String trimMargin([String marginPrefix = '|']) {
+    if (_inputIsNullOrBlank()) return _input;
+
+    final lines = LineSplitter.split(_input);
+    final buffer = StringBuffer();
+    var i = -1;
+
+    for (final line in lines) {
+      i++;
+
+      var result = line;
+      final leftTrimmedLine = line.trimLeft();
+
+      if ((i == 0 || i == lines.length - 1) &&
+          leftTrimmedLine.trimRight().isEmpty) {
+        // If this is the first or the last line, and it's just whitespace, we
+        // want to skip it.
+        continue;
+      }
+
+      if (leftTrimmedLine.length <= line.length) {
+        if (leftTrimmedLine.startsWith(marginPrefix)) {
+          result = leftTrimmedLine.replaceFirst(marginPrefix, '');
+        }
+      }
+
+      buffer.writeln(result);
+    }
+
+    return buffer.toString();
+  }
+
   // Turns the string into _Line classes that contain the indentation level and
   // unindented contents of each line.
   //
   // This is to avoid having to find the indentation level two times per line:
   // first time in the "find common indentation level" loop, and second time
   // in the loop that applies the indentation.
   Iterable<_Line> _processLines() sync* {
-    if (_valueIsNullOrBlank()) return;
+    if (_inputIsNullOrBlank()) return;
 
-    for (final line in LineSplitter.split(_value)) {
+    for (final line in LineSplitter.split(_input)) {
       final indentationMatch = _whitespace.stringMatch(line);
       final indentationLevel =
           indentationMatch != null && indentationMatch.isNotEmpty
@@ -129,8 +178,8 @@ class Indentation {
     }
   }
 
-  bool _valueIsNullOrBlank() =>
-      _value == null || _value.isEmpty || _value.trim().isEmpty;
+  bool _inputIsNullOrBlank() =>
+      _input == null || _input.isEmpty || _input.trim().isEmpty;
 
   int _findCommonIndentationLevel(Iterable<_Line> lines) {
     int commonIndentationLevel;

lib/src/string_extensions.dart

@@ -2,7 +2,7 @@ import 'indentation.dart';
 
 /// Extension methods for easier indentation of strings while preserving relative
 /// indentation.
-extension IndentedString on String {
+extension StringIndentation on String {
   /// Returns the indentation level of this string.
   ///
   /// An indentation level is determined by finding a non-empty line with the
@@ -88,4 +88,26 @@ extension IndentedString on String {
   ///  Hello
   /// World
   String indentBy(int howMuch) => Indentation(this).indentBy(howMuch);
+
+  /// Returns this string, but trims leading whitespace characters followed by the
+  /// given [marginPrefix] from each line.
+  ///
+  /// Also removes the first and last lines if they are blank, i.e. they only
+  /// contain whitespace characters.
+  ///
+  /// For example, given that the [marginPrefix] is "|" (the default), the input:
+  ///
+  ///       |   Hello
+  ///       | there
+  ///       |    World
+  ///
+  /// will become:
+  ///
+  ///    Hello
+  ///  there
+  ///     World
+  ///
+  /// Leaves lines that don't contain [marginPrefix] untouched.
+  String trimMargin([String marginPrefix = '|']) =>
+      Indentation(this).trimMargin(marginPrefix);
 }

pubspec.yaml

@@ -1,12 +1,13 @@
 name: indent
 description: Change indentation in multiline Dart strings while preserving the existing relative indentation.
-version: 1.0.0+2
+version: 1.1.0
 homepage: https://github.com/roughike/indent
 
 environment:
   sdk: '>=2.7.0 <3.0.0'
 
 dev_dependencies:
   expected_output: ^1.2.2
+  lint: ^1.0.0
   pedantic: ^1.8.0
   test: ^1.6.0

test/_indent_test.dart

@@ -5,19 +5,23 @@ import 'package:test/test.dart';
 import 'package:indent/indent.dart';
 
 void main() {
-  _runDatacase(
+  _runDataCase(
     'indentation_level_counts',
     (input) => input.getIndentationLevel(),
     (output) => int.parse(output),
   );
 
   // withIndentationLevel(0) and stripExtraIndentation are the same thing
-  _runDatacase('with_0_indentation', (input) => input.indent(0));
-  _runDatacase('with_0_indentation', (input) => input.unindent());
-  _runDatacase('with_3_indentation', (input) => input.indent(3));
+  _runDataCase('with_0_indentation', (input) => input.indent(0));
+  _runDataCase('with_0_indentation', (input) => input.unindent());
+  _runDataCase('with_3_indentation', (input) => input.indent(3));
 
-  _runDatacase('increase_indentation_by_3', (input) => input.indentBy(3));
-  _runDatacase('decrease_indentation_by_3', (input) => input.indentBy(-3));
+  _runDataCase('increase_indentation_by_3', (input) => input.indentBy(3));
+  _runDataCase('decrease_indentation_by_3', (input) => input.indentBy(-3));
+
+  _runDataCase('trim_margin_with_pipe', (input) => input.trimMargin());
+  _runDataCase('trim_margin_with_pipe', (input) => input.trimMargin('|'));
+  _runDataCase('trim_margin_with_hashbang', (input) => input.trimMargin('#!'));
 
   test('does not count empty line as indentation', () {
     expect(
@@ -37,7 +41,7 @@ void main() {
   });
 }
 
-void _runDatacase(
+void _runDataCase(
   String filename,
   dynamic Function(String) inputTransformer, [
   dynamic Function(String) outputTransformer,

test/trim_margin_with_hashbang.unit

@@ -0,0 +1,54 @@
+>>>
+    #!Tell me and I forget.
+    #!Teach me and I remember.
+    #!Involve me and I learn.
+    #!(Benjamin Franklin)
+<<<
+Tell me and I forget.
+Teach me and I remember.
+Involve me and I learn.
+(Benjamin Franklin)
+>>>
+    #!Tell me and I forget.
+ #!Teach me and I remember.
+   #!Involve me and I learn.
+  #!(Benjamin Franklin)
+<<<
+Tell me and I forget.
+Teach me and I remember.
+Involve me and I learn.
+(Benjamin Franklin)
+>>> preserves leading whitespace for lines not containing marginPrefix
+    #!Tell me and I forget.
+ #!Teach me and I remember.
+   Involve me and I learn.
+  #!(Benjamin Franklin)
+<<<
+Tell me and I forget.
+Teach me and I remember.
+   Involve me and I learn.
+(Benjamin Franklin)
+>>> trims first and last lines if they are blank
+
+    #!Tell me and I forget.
+    #!Teach me and I remember.
+    #!Involve me and I learn.
+    #!(Benjamin Franklin)
+
+<<<
+Tell me and I forget.
+Teach me and I remember.
+Involve me and I learn.
+(Benjamin Franklin)
+>>> trims marginPrefix even without preceding whitespace
+
+#!Tell me and I forget.
+#!Teach me and I remember.
+#!Involve me and I learn.
+#!(Benjamin Franklin)
+
+<<<
+Tell me and I forget.
+Teach me and I remember.
+Involve me and I learn.
+(Benjamin Franklin)