Improve auto indenting by removing a hard coded restriction and adding a 3rd regexp

Currently there are only two regexps that can influence the indents.
Those are `increaseIndentPattern` (which tells Atom the indent of next
line should be increased) and `decreaseIndentPattern` (which tells Atom
the indent of the current line should be decreased).

But I found that a couple of languages would need a 3rd regexp in order
to support their use cases. This 3rd regexp should be a mixture of the
existing two so it tells Atom that the indent of the next line should
decrease.

I’ll add a screencast to show a use case for this 3rd regexp which I
would like to call `decreaseNextIndentPattern`.

src/language-mode.coffee

@@ -246,8 +246,12 @@ class LanguageMode
     iterator.next()
     scopeDescriptor = new ScopeDescriptor(scopes: iterator.getScopes())
 
+    increaseIndentRegex = @increaseIndentRegexForScopeDescriptor(scopeDescriptor)
+    decreaseIndentRegex = @decreaseIndentRegexForScopeDescriptor(scopeDescriptor)
+    decreaseNextIndentRegex = @decreaseNextIndentRegexForScopeDescriptor(scopeDescriptor)
+
     currentIndentLevel = @editor.indentationForBufferRow(bufferRow)
-    return currentIndentLevel unless increaseIndentRegex = @increaseIndentRegexForScopeDescriptor(scopeDescriptor)
+    return currentIndentLevel unless increaseIndentRegex
 
     if options?.skipBlankLines ? true
       precedingRow = @buffer.previousNonBlankRow(bufferRow)
@@ -256,13 +260,17 @@ class LanguageMode
       precedingRow = bufferRow - 1
       return currentIndentLevel if precedingRow < 0
 
-    precedingLine = @buffer.lineForRow(precedingRow)
     desiredIndentLevel = @editor.indentationForBufferRow(precedingRow)
-    desiredIndentLevel += 1 if increaseIndentRegex.testSync(precedingLine) and not @editor.isBufferRowCommented(precedingRow)
+    return desiredIndentLevel if @buffer.isRowBlank(precedingRow)
 
-    return desiredIndentLevel unless decreaseIndentRegex = @decreaseIndentRegexForScopeDescriptor(scopeDescriptor)
-    line = @buffer.lineForRow(bufferRow)
-    desiredIndentLevel -= 1 if decreaseIndentRegex.testSync(line)
+    unless @editor.isBufferRowCommented(precedingRow)
+      precedingLine = @buffer.lineForRow(precedingRow)
+      desiredIndentLevel += 1 if increaseIndentRegex?.testSync(precedingLine)
+      desiredIndentLevel -= 1 if decreaseNextIndentRegex?.testSync(precedingLine)
+
+    unless @editor.isBufferRowCommented(bufferRow)
+      bufferLine = @buffer.lineForRow(bufferRow)
+      desiredIndentLevel -= 1 if decreaseIndentRegex?.testSync(bufferLine)
 
     Math.max(desiredIndentLevel, 0)
 
@@ -298,21 +306,26 @@ class LanguageMode
   # bufferRow - The row {Number}
   autoDecreaseIndentForBufferRow: (bufferRow) ->
     scopeDescriptor = @editor.scopeDescriptorForBufferPosition([bufferRow, 0])
-    increaseIndentRegex = @increaseIndentRegexForScopeDescriptor(scopeDescriptor)
-    decreaseIndentRegex = @decreaseIndentRegexForScopeDescriptor(scopeDescriptor)
-    return unless increaseIndentRegex and decreaseIndentRegex
+    return unless decreaseIndentRegex = @decreaseIndentRegexForScopeDescriptor(scopeDescriptor)
 
     line = @buffer.lineForRow(bufferRow)
     return unless decreaseIndentRegex.testSync(line)
 
     currentIndentLevel = @editor.indentationForBufferRow(bufferRow)
     return if currentIndentLevel is 0
+
     precedingRow = @buffer.previousNonBlankRow(bufferRow)
     return unless precedingRow?
-    precedingLine = @buffer.lineForRow(precedingRow)
 
+    precedingLine = @buffer.lineForRow(precedingRow)
     desiredIndentLevel = @editor.indentationForBufferRow(precedingRow)
-    desiredIndentLevel -= 1 unless increaseIndentRegex.testSync(precedingLine)
+
+    if increaseIndentRegex = @increaseIndentRegexForScopeDescriptor(scopeDescriptor)
+      desiredIndentLevel -= 1 unless increaseIndentRegex.testSync(precedingLine)
+
+    if decreaseNextIndentRegex = @decreaseNextIndentRegexForScopeDescriptor(scopeDescriptor)
+      desiredIndentLevel -= 1 if decreaseNextIndentRegex.testSync(precedingLine)
+
     if desiredIndentLevel >= 0 and desiredIndentLevel < currentIndentLevel
       @editor.setIndentationForBufferRow(bufferRow, desiredIndentLevel)
 
@@ -326,6 +339,9 @@ class LanguageMode
   decreaseIndentRegexForScopeDescriptor: (scopeDescriptor) ->
     @getRegexForProperty(scopeDescriptor, 'editor.decreaseIndentPattern')
 
+  decreaseNextIndentRegexForScopeDescriptor: (scopeDescriptor) ->
+    @getRegexForProperty(scopeDescriptor, 'editor.decreaseNextIndentPattern')
+
   foldEndRegexForScopeDescriptor: (scopeDescriptor) ->
     @getRegexForProperty(scopeDescriptor, 'editor.foldEndPattern')
 

src/selection.coffee

@@ -395,10 +395,7 @@ class Selection extends Model
       @editor.setIndentationForBufferRow(oldBufferRange.start.row, desiredIndentLevel)
 
     if options.autoIndentNewline and text is '\n'
-      currentIndentation = @editor.indentationForBufferRow(newBufferRange.start.row)
       @editor.autoIndentBufferRow(newBufferRange.end.row, preserveLeadingWhitespace: true, skipBlankLines: false)
-      if @editor.indentationForBufferRow(newBufferRange.end.row) < currentIndentation
-        @editor.setIndentationForBufferRow(newBufferRange.end.row, currentIndentation)
     else if options.autoDecreaseIndent and NonWhitespaceRegExp.test(text)
       @editor.autoDecreaseIndentForBufferRow(newBufferRange.start.row)