mformat: better handling of continuation lines

Fixes mesonbuild#13566. Fixes mesonbuild#13567.

mesonbuild/mformat.py

@@ -276,6 +276,7 @@ def exit_node(self, node: mparser.BaseNode) -> None:
 
     def move_whitespaces(self, from_node: mparser.BaseNode, to_node: mparser.BaseNode) -> None:
         to_node.whitespaces.value = from_node.whitespaces.value + to_node.whitespaces.value
+        to_node.whitespaces.is_continuation = from_node.whitespaces.is_continuation
         from_node.whitespaces = None
         to_node.whitespaces.accept(self)
 
@@ -317,7 +318,10 @@ def visit_WhitespaceNode(self, node: mparser.WhitespaceNode) -> None:
         for i, line in enumerate(lines):
             has_nl = line.endswith('\n')
             line = line.strip()
-            if line.startswith('#'):
+            if line.startswith('\\'):
+                node.value += ' '  # add space before \
+                node.is_continuation = True
+            elif line.startswith('#'):
                 if not in_block_comments:
                     node.value += self.config.indent_before_comments
                 else:
@@ -328,6 +332,8 @@ def visit_WhitespaceNode(self, node: mparser.WhitespaceNode) -> None:
             in_block_comments = True
         if node.value.endswith('\n'):
             node.value += self.indent_comments
+            if node.is_continuation:
+                node.value += self.config.indent_by
 
     def visit_SymbolNode(self, node: mparser.SymbolNode) -> None:
         super().visit_SymbolNode(node)
@@ -595,13 +601,18 @@ def visit_DictNode(self, node: mparser.DictNode) -> None:
     def visit_MethodNode(self, node: mparser.MethodNode) -> None:
         self.enter_node(node)
         node.source_object.accept(self)
+        is_cont = node.source_object.whitespaces and node.source_object.whitespaces.is_continuation
+        if is_cont:
+            self.level += 1
         if node.args.is_multiline:
             self.level += 1
             self.add_nl_after(node.lpar, indent=self.level)
         self.is_function_arguments = True
         node.args.accept(self)
         if node.args.is_multiline:
             self.level -= 1
+        if is_cont:
+            self.level -= 1
         self.exit_node(node)
 
     def visit_FunctionNode(self, node: mparser.FunctionNode) -> None:

mesonbuild/mparser.py

@@ -267,6 +267,7 @@ def __init__(self, token: Token[str]):
         self.value = ''
         self.append(token)
         self.block_indent = False
+        self.is_continuation = False
 
     def append(self, token: Token[str]) -> None:
         self.value += token.value

test cases/format/1 default/meson.build

@@ -13,6 +13,16 @@ meson_files = {
 # Ensure empty function are formatted correctly on long lines
 a = '@0@@1@@2@@3@@4@'.format('one', 'two', 'three', 'four', 'five').strip().strip()
 
+_opt = get_option('opt') \
+    .disable_if(
+        true,
+        error_message: 'This is an error message because opt can\'t be enabled',
+    ) \
+    .enable_if(
+        false,
+        error_message: 'This is an error message because opt can\'t be disabled',
+    )
+
 foreach name, f : meson_files
     test(name, meson_cmd, args: ['format', '--check-only', f])
 endforeach

test cases/format/1 default/meson.options

@@ -0,0 +1 @@
+option('opt', type : 'feature', value : 'auto')