Rework handling of line breaks and indentation

The capturing of line breaks and indentation was pretty weird to avoid
ambiguity. This strategy gets exponentially more complicated when adding
nested control structures. I now understand conflicts and dynamic
precedence better, which is now used to handle the ambiguity instead.

grammar.js

@@ -67,6 +67,14 @@ module.exports = grammar({
 
   extras: $ => [$.comment],
 
+  conflicts: $ => [
+    // Because of the $._line_break in $.continuation
+    [$.arguments],   
+
+    // Because of the $._line_break in IF/ELSE/WHILE/FOR etc.
+    [$.block],
+  ],
+
   rules: {
     source_file: $ => seq(
       optional(/\s+/), // Allows whitespace before the first section
@@ -95,6 +103,7 @@ module.exports = grammar({
       choice(...SETTINGS_KEYWORDS.map(caseInsensitive)),
       $._separator,
       $.arguments,
+      $._line_break,
     ),
 
     //
@@ -115,6 +124,7 @@ module.exports = grammar({
       ),
       $._separator,
       $.arguments,
+      $._line_break,
     ),
 
     //
@@ -133,10 +143,11 @@ module.exports = grammar({
       $._line_break,
       alias($.keyword_definition_body, $.body),
     ),
+    // prec.right is needed to capture $._empty_line more strongly than $.keywords_section
     keyword_definition_body: $ => prec.right(repeat1(
       choice(
-        seq($._indentation, $.keyword_setting),
-        seq($._indentation, $.statement),
+        seq($._indentation, $.keyword_setting, $._line_break),
+        seq($._indentation, $.statement, $._line_break),
         $._empty_line,
       )
     )),
@@ -171,7 +182,8 @@ module.exports = grammar({
         // Data-driven tests have arguments
         seq(
           $._separator,
-          $.arguments,
+          alias($.arguments_without_continuation, $.arguments),
+          $._line_break,
         ),
 
         // Regular tests have bodies
@@ -181,10 +193,11 @@ module.exports = grammar({
         )
       )
     ),
+    // prec.right is needed to capture $._empty_line more strongly than $.test_case_section
     test_case_definition_body: $ => prec.right(repeat1(
       choice(
-        seq($._indentation, $.test_case_setting),
-        seq($._indentation, $.statement),
+        seq($._indentation, $.test_case_setting, $._line_break),
+        seq($._indentation, $.statement, $._line_break),
         $._empty_line,
       )
     )),
@@ -235,64 +248,57 @@ module.exports = grammar({
       optional(
         choice("=", " =")
       ),
-      choice(
-        seq(
-          $._separator,
-          $.arguments,
-        ),
-        $._line_break,
-      ),
+      optional(seq(
+        $._separator,
+        $.arguments,
+      )),
     ),
 
     keyword_invocation: $ => seq(
       alias($.text_chunk, $.keyword),
-      choice(
-        seq(
-          $._separator,
-          $.arguments,
-        ),
-        $._line_break,
-      ),
+      optional(seq(
+        $._separator,
+        $.arguments,
+      )),
     ),
 
     if_statement: $ => seq(
       "IF",
       $._separator,
       field("condition", $.argument),
       $._line_break,
-      $._indentation,
 
       optional(field("consequence", $.block)),
 
       repeat(field("alternative", $.elseif_statement)),
 
       optional(field("alternative", $.else_statement)),
 
-      "END",
+      seq($._indentation, "END"),
     ),
 
-    elseif_statement: $ => seq(
+    // Conflicts with parent structures because of $._line_break
+    elseif_statement: $ => prec.dynamic(100, seq(
+      $._indentation,
       "ELSE IF",
       $._separator,
       field("condition", $.argument),
       $._line_break,
-      $._indentation,
       field("consequence", $.block),
-    ),
+    )),
 
-    else_statement: $ => seq(
+    // Conflicts with parent structures because of $._line_break
+    else_statement: $ => prec.dynamic(100, seq(
+      $._indentation,
       "ELSE",
-      seq(
-        $._line_break,
-        $._indentation,
-        $.block,
-      )
-    ),
+      $._line_break,
+      field("consequence", $.block),
+    )),
 
     block: $ => repeat1(
       choice(
-        $._line_break,
-        seq($.statement, $._indentation),
+        $._empty_line,
+        seq($._indentation, $.statement, $._line_break),
       )
     ),
 
@@ -306,22 +312,28 @@ module.exports = grammar({
         $._separator,
         $.argument,
       )),
-      $._line_break,
       repeat($.continuation),
     ),
 
-    continuation: $ => seq(
-      choice(
-        $.ellipses,
-        alias($.indented_ellipses, $.ellipses),
-      ),
+    arguments_without_continuation: $ => seq(
+      $.argument,
       repeat(seq(
         $._separator,
         $.argument,
       )),
-      $._line_break,
     ),
 
+    // Conflicts with parent structures because of $._line_break
+    continuation: $ => prec.dynamic(100, seq(
+      $._line_break,
+      optional($._indentation),
+      $.ellipses,
+      repeat(seq(
+        $._separator,
+        $.argument,
+      )),
+    )),
+
     ellipses: $ => "...",
     indented_ellipses: $ => token(seq(
       /[ ]{2}|\t/,
@@ -399,7 +411,7 @@ module.exports = grammar({
 
     _whitespace: $ => /[ \t]+/,
 
-    _line_break: $ => /\r\n|\r|\n/,
+    _line_break: $ => /\s*\r\n|\r|\n/,
 
     _empty_line: $ => seq(optional(/[ \t]+/), $._line_break),
   },