meson format command

3 files changed, 985 insertions, 1 deletions

diff --git a/mesonbuild/mesonmain.py b/mesonbuild/mesonmain.py
index c01be49e5..62ed8918c 100644
--- a/mesonbuild/mesonmain.py
+++ b/mesonbuild/mesonmain.py
@@ -61,7 +61,7 @@ def errorhandler(e: Exception, command: str) -> int:
 class CommandLineParser:
     def __init__(self) -> None:
         # only import these once we do full argparse processing
-        from . import mconf, mdist, minit, minstall, mintro, msetup, mtest, rewriter, msubprojects, munstable_coredata, mcompile, mdevenv
+        from . import mconf, mdist, minit, minstall, mintro, msetup, mtest, rewriter, msubprojects, munstable_coredata, mcompile, mdevenv, mformat
         from .scripts import env2mfile
         from .wrap import wraptool
         import shutil
@@ -100,6 +100,8 @@ class CommandLineParser:
                          help_msg='Run commands in developer environment')
         self.add_command('env2mfile', env2mfile.add_arguments, env2mfile.run,
                          help_msg='Convert current environment to a cross or native file')
+        self.add_command('format', mformat.add_arguments, mformat.run, aliases=['fmt'],
+                         help_msg='Format meson source file')
         # Add new commands above this line to list them in help command
         self.add_command('help', self.add_help_arguments, self.run_help_command,
                          help_msg='Print help of a subcommand')
diff --git a/mesonbuild/mformat.py b/mesonbuild/mformat.py
new file mode 100644
index 000000000..49ece4f03
--- /dev/null
+++ b/mesonbuild/mformat.py
@@ -0,0 +1,979 @@
+# SPDX-License-Identifier: Apache-2.0
+# Copyright 2024 The Meson development team
+
+from __future__ import annotations
+
+import argparse
+import re
+import typing as T
+from configparser import ConfigParser, MissingSectionHeaderError
+from copy import deepcopy
+from dataclasses import dataclass, field, fields, asdict
+from pathlib import Path
+
+from . import mparser
+from .mesonlib import MesonException
+from .ast.postprocess import AstConditionLevel
+from .ast.printer import RawPrinter
+from .ast.visitor import FullAstVisitor
+from .environment import build_filename
+
+if T.TYPE_CHECKING:
+    from typing_extensions import Literal
+
+
+class DefaultConfigParser(ConfigParser):
+
+    def __init__(self, delimiters: T.Tuple[str, ...] = ('=', ':')):
+        super().__init__(delimiters=delimiters, interpolation=None)
+
+    def read_default(self, filename: Path) -> None:
+        if not filename.exists():
+            raise MesonException(f'Configuration file {filename} not found')
+        try:
+            super().read(filename, encoding='utf-8')
+        except MissingSectionHeaderError:
+            self.read_string(f'[{self.default_section}]\n' + filename.read_text(encoding='utf-8'))
+
+    def getstr(self, section: str, key: str, fallback: T.Optional[str] = None) -> T.Optional[str]:
+        value: T.Optional[str] = self.get(section, key, fallback=fallback)
+        if value:
+            value = value.strip('"').strip("'")
+        return value
+
+
+def match_path(filename: str, pattern: str) -> bool:
+    '''recursive glob match for editorconfig sections'''
+    index = 0
+    num_ranges: T.List[T.Tuple[int, int]] = []
+
+    def curl_replace(m: re.Match) -> str:
+        nonlocal index
+
+        if '\\.\\.' in m[1]:
+            index += 1
+            low, high = m[1].split('\\.\\.')
+            num_ranges.append((int(low), int(high)))
+            return f'(?P<num{index}>-?[0-9]+)'
+        else:
+            return T.cast(str, m[1].replace(',', '|'))
+
+    pattern_re = pattern.replace('.', '\\.')
+    pattern_re = re.sub(r'(?<!\\)\?', '.', pattern_re)  # ? -> .
+    pattern_re = re.sub(r'(?<![\\\*])\*(?!\*)', '([^/]*)', pattern_re)  # * -> ([^/]*)
+    pattern_re = re.sub(r'(?<!\\)\*\*', '(.*)', pattern_re)  # ** -> (.*)
+    pattern_re = re.sub(r'(?<!\\)\[!(.*?[^\\])\]', r'([^\1])', pattern_re)  # [!name] -> [^name]
+    pattern_re = re.sub(r'(?<!\\)\{(.*?[^\\])}', curl_replace, pattern_re)  # {}
+    if pattern.startswith('/'):
+        pattern_re = '^' + pattern_re
+    pattern_re += '$'
+
+    m = re.search(pattern_re, filename)
+    if m is None:
+        return False
+
+    for i in range(index):
+        try:
+            val = int(m[f'num{i+1}'])
+            if not num_ranges[i][0] <= val <= num_ranges[i][1]:
+                return False
+        except ValueError:
+            return False
+
+    return True
+
+
+@dataclass
+class EditorConfig:
+
+    indent_style: T.Optional[Literal['space', 'tab']] = field(default=None, metadata={'getter': DefaultConfigParser.get})
+    indent_size: T.Optional[int] = field(default=None, metadata={'getter': DefaultConfigParser.getint})
+    tab_width: T.Optional[int] = field(default=None, metadata={'getter': DefaultConfigParser.getint})
+    end_of_line: T.Optional[Literal['lf', 'cr', 'crlf']] = field(default=None, metadata={'getter': DefaultConfigParser.get})
+    charset: T.Optional[Literal['latin1', 'utf-8', 'utf-8-bom', 'utf-16be', 'utf-16le']] = field(default=None, metadata={'getter': DefaultConfigParser.get})
+    trim_trailing_whitespace: T.Optional[bool] = field(default=None, metadata={'getter': DefaultConfigParser.getboolean})
+    insert_final_newline: T.Optional[bool] = field(default=None, metadata={'getter': DefaultConfigParser.getboolean})
+    max_line_length: T.Optional[T.Union[Literal['off'], int]] = field(default=None, metadata={'getter': DefaultConfigParser.get})
+
+
+@dataclass
+class FormatterConfig:
+
+    # Config keys compatible with muon
+    max_line_length: T.Optional[int] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getint,
+                  'default': 80,
+                  })
+    indent_by: T.Optional[str] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getstr,
+                  'default': '    ',
+                  })
+    space_array: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': False,
+                  })
+    kwargs_force_multiline: T.Optional[bool] = field(
+        default=None,  # kwa_ml
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': False,
+                  })
+    wide_colon: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': False,
+                  })
+    no_single_comma_function: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': False,
+                  })
+
+    # Additional config keys
+    end_of_line: T.Optional[Literal['cr', 'lf', 'crlf', 'native']] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getstr,
+                  'default': 'native',
+                  })
+    indent_before_comments: T.Optional[str] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getstr,
+                  'default': '  ',
+                  })
+    simplify_string_literals: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': True,
+                  })
+    insert_final_newline: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': True,
+                  })
+    tab_width: T.Optional[int] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getint,
+                  'default': 4,
+                  }
+    )
+    sort_files: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': True,
+                  })
+    group_arg_value: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': False,
+                  })
+    use_editor_config: T.Optional[bool] = field(
+        default=None,
+        metadata={'getter': DefaultConfigParser.getboolean,
+                  'default': False,
+                  })
+
+    @classmethod
+    def default(cls) -> FormatterConfig:
+        defaults = {f.name: f.metadata['default'] for f in fields(cls)}
+        return cls(**defaults)
+
+    def update(self, config: FormatterConfig) -> FormatterConfig:
+        """Returns copy of self updated with other config"""
+        new_config = deepcopy(self)
+        for key, value in asdict(config).items():
+            if value is not None:
+                setattr(new_config, key, value)
+        return new_config
+
+    def with_editorconfig(self, editorconfig: EditorConfig) -> FormatterConfig:
+        """Returns copy of self updated with editorconfig"""
+        config = deepcopy(self)
+
+        if editorconfig.indent_style == 'space':
+            indent_size = editorconfig.indent_size or 4
+            config.indent_by = indent_size * ' '
+        elif editorconfig.indent_style == 'tab':
+            config.indent_by = '\t'
+        elif editorconfig.indent_size:
+            config.indent_by = editorconfig.indent_size * ' '
+
+        if editorconfig.max_line_length == 'off':
+            config.max_line_length = 0
+        elif editorconfig.max_line_length:
+            config.max_line_length = int(editorconfig.max_line_length)
+
+        if editorconfig.end_of_line:
+            config.end_of_line = editorconfig.end_of_line
+        if editorconfig.insert_final_newline:
+            config.insert_final_newline = editorconfig.insert_final_newline
+        if editorconfig.tab_width:
+            config.tab_width = editorconfig.tab_width
+
+        return config
+
+    @property
+    def newline(self) -> T.Optional[str]:
+        if self.end_of_line == 'crlf':
+            return '\r\n'
+        if self.end_of_line == 'lf':
+            return '\n'
+        if self.end_of_line == 'cr':
+            return '\r'
+        return None
+
+
+class MultilineArgumentDetector(FullAstVisitor):
+
+    def __init__(self, config: FormatterConfig):
+        self.config = config
+        self.is_multiline = False
+
+    def enter_node(self, node: mparser.BaseNode) -> None:
+        if node.whitespaces and '#' in node.whitespaces.value:
+            self.is_multiline = True
+
+        elif isinstance(node, mparser.StringNode) and node.is_multiline:
+            self.is_multiline = True
+
+    def visit_ArgumentNode(self, node: mparser.ArgumentNode) -> None:
+        if node.is_multiline:
+            self.is_multiline = True
+
+        if self.is_multiline:
+            return
+
+        if self.config.kwargs_force_multiline and node.kwargs:
+            self.is_multiline = True
+
+        super().visit_ArgumentNode(node)
+
+
+class TrimWhitespaces(FullAstVisitor):
+
+    def __init__(self, config: FormatterConfig):
+        self.config = config
+
+        self.in_block_comments = False
+        self.in_arguments = 0
+        self.indent_comments = ''
+
+    def visit_default_func(self, node: mparser.BaseNode) -> None:
+        self.enter_node(node)
+        node.whitespaces.accept(self)
+
+    def enter_node(self, node: mparser.BaseNode) -> None:
+        if isinstance(node, mparser.WhitespaceNode):
+            return
+        if not node.whitespaces:
+            # Ensure every node has a whitespace node
+            node.whitespaces = mparser.WhitespaceNode(mparser.Token('whitespace', node.filename, 0, 0, 0, (0, 0), ''))
+            node.whitespaces.condition_level = node.condition_level
+
+    def exit_node(self, node: mparser.BaseNode) -> None:
+        pass
+
+    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
+        from_node.whitespaces = None
+        to_node.whitespaces.accept(self)
+
+    def add_space_after(self, node: mparser.BaseNode) -> None:
+        if not node.whitespaces.value:
+            node.whitespaces.value = ' '
+
+    def add_nl_after(self, node: mparser.BaseNode, force: bool = False) -> None:
+        if not node.whitespaces.value:
+            node.whitespaces.value = '\n'
+        elif force and not node.whitespaces.value.endswith('\n'):
+            node.whitespaces.value += '\n'
+
+    def dedent(self, value: str) -> str:
+        if value.endswith(self.config.indent_by):
+            value = value[:-len(self.config.indent_by)]
+        return value
+
+    def sort_arguments(self, node: mparser.ArgumentNode) -> None:
+        # TODO: natsort
+        def sort_key(arg: mparser.BaseNode) -> str:
+            if isinstance(arg, mparser.StringNode):
+                return arg.raw_value
+            return getattr(node, 'value', '')
+
+        node.arguments.sort(key=sort_key)
+
+    def visit_EmptyNode(self, node: mparser.EmptyNode) -> None:
+        self.enter_node(node)
+        self.in_block_comments = True
+        node.whitespaces.accept(self)
+        self.in_block_comments = False
+
+    def visit_WhitespaceNode(self, node: mparser.WhitespaceNode) -> None:
+        lines = node.value.splitlines(keepends=True)
+        node.value = ''
+        in_block_comments = self.in_block_comments
+        with_comments = ['#' in line for line in lines] + [False]
+        for i, line in enumerate(lines):
+            has_nl = line.endswith('\n')
+            line = line.strip()
+            if line.startswith('#'):
+                if not in_block_comments:
+                    node.value += self.config.indent_before_comments
+                else:
+                    node.value += self.indent_comments
+            node.value += line
+            if has_nl and (line or with_comments[i+1] or not self.in_arguments):
+                node.value += '\n'
+            in_block_comments = True
+        if node.value.endswith('\n'):
+            node.value += self.indent_comments
+
+    def visit_SymbolNode(self, node: mparser.SymbolNode) -> None:
+        super().visit_SymbolNode(node)
+        if node.value in "([{" and node.whitespaces.value == '\n':
+            node.whitespaces.value = ''
+
+    def visit_StringNode(self, node: mparser.StringNode) -> None:
+        self.enter_node(node)
+
+        if self.config.simplify_string_literals:
+            if node.is_multiline and '\n' not in node.value:
+                node.is_multiline = False
+                node.value = node.escape()
+
+            if node.is_fstring and '@' not in node.value:
+                node.is_fstring = False
+
+        self.exit_node(node)
+
+    def visit_UnaryOperatorNode(self, node: mparser.UnaryOperatorNode) -> None:
+        super().visit_UnaryOperatorNode(node)
+        self.move_whitespaces(node.value, node)
+
+    def visit_NotNode(self, node: mparser.NotNode) -> None:
+        super().visit_UnaryOperatorNode(node)
+        if not node.operator.whitespaces.value:
+            node.operator.whitespaces.value = ' '
+        self.move_whitespaces(node.value, node)
+
+    def visit_BinaryOperatorNode(self, node: mparser.BinaryOperatorNode) -> None:
+        super().visit_BinaryOperatorNode(node)
+        self.add_space_after(node.left)
+        self.add_space_after(node.operator)
+        self.move_whitespaces(node.right, node)
+
+    def visit_ArrayNode(self, node: mparser.ArrayNode) -> None:
+        super().visit_ArrayNode(node)
+        self.move_whitespaces(node.rbracket, node)
+
+        if node.lbracket.whitespaces.value:
+            node.args.is_multiline = True
+        if node.args.arguments and not node.args.is_multiline and self.config.space_array:
+            self.add_space_after(node.lbracket)
+            self.add_space_after(node.args)
+
+    def visit_DictNode(self, node: mparser.DictNode) -> None:
+        super().visit_DictNode(node)
+        self.move_whitespaces(node.rcurl, node)
+
+        if node.lcurl.whitespaces.value:
+            node.args.is_multiline = True
+
+    def visit_CodeBlockNode(self, node: mparser.CodeBlockNode) -> None:
+        self.enter_node(node)
+        if node.pre_whitespaces:
+            self.in_block_comments = True
+            node.pre_whitespaces.accept(self)
+            self.in_block_comments = False
+        else:
+            node.pre_whitespaces = mparser.WhitespaceNode(mparser.Token('whitespace', node.filename, 0, 0, 0, (0, 0), ''))
+
+        for i in node.lines:
+            i.accept(self)
+        self.exit_node(node)
+
+        if node.lines:
+            self.move_whitespaces(node.lines[-1], node)
+        else:
+            node.whitespaces.accept(self)
+
+        if node.condition_level == 0 and self.config.insert_final_newline:
+            self.add_nl_after(node, force=True)
+
+        indent = node.condition_level * self.config.indent_by
+        if indent and node.lines:
+            node.pre_whitespaces.value += indent
+        for line in node.lines[:-1]:
+            line.whitespaces.value += indent
+
+    def visit_IndexNode(self, node: mparser.IndexNode) -> None:
+        super().visit_IndexNode(node)
+        self.move_whitespaces(node.rbracket, node)
+
+    def visit_MethodNode(self, node: mparser.MethodNode) -> None:
+        super().visit_MethodNode(node)
+        self.move_whitespaces(node.rpar, node)
+
+        if node.lpar.whitespaces.value:
+            node.args.is_multiline = True
+
+    def visit_FunctionNode(self, node: mparser.FunctionNode) -> None:
+        if node.func_name.value == 'files':
+            if self.config.sort_files:
+                self.sort_arguments(node.args)
+
+            if len(node.args.arguments) == 1 and not node.args.kwargs:
+                arg = node.args.arguments[0]
+                if isinstance(arg, mparser.ArrayNode):
+                    if not arg.lbracket.whitespaces or not arg.lbracket.whitespaces.value.strip():
+                        # files([...]) -> files(...)
+                        node.args = arg.args
+
+        super().visit_FunctionNode(node)
+        self.move_whitespaces(node.rpar, node)
+
+        if node.lpar.whitespaces.value:
+            node.args.is_multiline = True
+
+    def visit_AssignmentNode(self, node: mparser.AssignmentNode) -> None:
+        super().visit_AssignmentNode(node)
+        self.add_space_after(node.var_name)
+        self.add_space_after(node.operator)
+        self.move_whitespaces(node.value, node)
+
+    def visit_ForeachClauseNode(self, node: mparser.ForeachClauseNode) -> None:
+        super().visit_ForeachClauseNode(node)
+        self.add_space_after(node.foreach_)
+        self.add_space_after(node.varnames[-1])
+        for comma in node.commas:
+            self.add_space_after(comma)
+        self.add_space_after(node.colon)
+
+        node.block.whitespaces.value += node.condition_level * self.config.indent_by
+
+        self.move_whitespaces(node.endforeach, node)
+
+    def visit_IfClauseNode(self, node: mparser.IfClauseNode) -> None:
+        super().visit_IfClauseNode(node)
+        self.move_whitespaces(node.endif, node)
+
+        if isinstance(node.elseblock, mparser.ElseNode):
+            node.elseblock.whitespaces.value += node.condition_level * self.config.indent_by
+        else:
+            node.ifs[-1].whitespaces.value += node.condition_level * self.config.indent_by
+
+    def visit_IfNode(self, node: mparser.IfNode) -> None:
+        super().visit_IfNode(node)
+        self.add_space_after(node.if_)
+        self.move_whitespaces(node.block, node)
+
+    def visit_ElseNode(self, node: mparser.ElseNode) -> None:
+        super().visit_ElseNode(node)
+        self.move_whitespaces(node.block, node)
+
+    def visit_TernaryNode(self, node: mparser.TernaryNode) -> None:
+        super().visit_TernaryNode(node)
+        self.add_space_after(node.condition)
+        self.add_space_after(node.questionmark)
+        self.add_space_after(node.trueblock)
+        self.add_space_after(node.colon)
+        self.move_whitespaces(node.falseblock, node)
+
+    def visit_ArgumentNode(self, node: mparser.ArgumentNode) -> None:
+        if not node.is_multiline:
+            ml_detector = MultilineArgumentDetector(self.config)
+            node.accept(ml_detector)
+            if ml_detector.is_multiline:
+                node.is_multiline = True
+
+        self.in_arguments += 1
+        super().visit_ArgumentNode(node)
+        self.in_arguments -= 1
+
+        if not node.arguments and not node.kwargs:
+            node.whitespaces.accept(self)
+            return
+
+        last_node: mparser.BaseNode
+        has_trailing_comma = len(node.commas) == len(node.arguments) + len(node.kwargs)
+        if has_trailing_comma:
+            last_node = node.commas[-1]
+        elif node.kwargs:
+            for last_node in node.kwargs.values():
+                pass
+        else:
+            last_node = node.arguments[-1]
+
+        self.move_whitespaces(last_node, node)
+
+        if not node.is_multiline and '#' not in node.whitespaces.value:
+            node.whitespaces.value = ''
+
+    def visit_ParenthesizedNode(self, node: mparser.ParenthesizedNode) -> None:
+        self.enter_node(node)
+
+        is_multiline = node.lpar.whitespaces and '#' in node.lpar.whitespaces.value
+        if is_multiline:
+            self.indent_comments += self.config.indent_by
+
+        node.lpar.accept(self)
+        node.inner.accept(self)
+
+        if is_multiline:
+            node.inner.whitespaces.value = self.dedent(node.inner.whitespaces.value)
+            self.indent_comments = self.dedent(self.indent_comments)
+            self.add_nl_after(node.inner)
+
+        node.rpar.accept(self)
+        self.move_whitespaces(node.rpar, node)
+
+
+class ArgumentFormatter(FullAstVisitor):
+
+    def __init__(self, config: FormatterConfig):
+        self.config = config
+        self.level = 0
+        self.indent_after = False
+        self.is_function_arguments = False
+
+    def add_space_after(self, node: mparser.BaseNode) -> None:
+        if not node.whitespaces.value:
+            node.whitespaces.value = ' '
+
+    def add_nl_after(self, node: mparser.BaseNode, indent: int) -> None:
+        if not node.whitespaces.value or node.whitespaces.value == ' ':
+            node.whitespaces.value = '\n'
+        indent_by = (node.condition_level + indent) * self.config.indent_by
+        if indent_by:
+            node.whitespaces.value += indent_by
+
+    def visit_ArrayNode(self, node: mparser.ArrayNode) -> None:
+        self.enter_node(node)
+        if node.args.is_multiline:
+            self.level += 1
+            self.add_nl_after(node.lbracket, indent=self.level)
+        self.is_function_arguments = False
+        node.args.accept(self)
+        if node.args.is_multiline:
+            self.level -= 1
+        self.exit_node(node)
+
+    def visit_DictNode(self, node: mparser.DictNode) -> None:
+        self.enter_node(node)
+        if node.args.is_multiline:
+            self.level += 1
+            self.add_nl_after(node.lcurl, indent=self.level)
+        self.is_function_arguments = False
+        node.args.accept(self)
+        if node.args.is_multiline:
+            self.level -= 1
+        self.exit_node(node)
+
+    def visit_MethodNode(self, node: mparser.MethodNode) -> None:
+        self.enter_node(node)
+        node.source_object.accept(self)
+        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
+        self.exit_node(node)
+
+    def visit_FunctionNode(self, node: mparser.FunctionNode) -> None:
+        self.enter_node(node)
+        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
+        self.exit_node(node)
+
+    def visit_WhitespaceNode(self, node: mparser.WhitespaceNode) -> None:
+        lines = node.value.splitlines(keepends=True)
+        if lines:
+            indent = (node.condition_level + self.level) * self.config.indent_by
+            node.value = lines[0]
+            for line in lines[1:]:
+                if '#' in line and not line.startswith(indent):
+                    node.value += indent
+                node.value += line
+            if self.indent_after and node.value.endswith(('\n', self.config.indent_by)):
+                node.value += indent
+
+    def visit_ArgumentNode(self, node: mparser.ArgumentNode) -> None:
+        is_function_arguments = self.is_function_arguments  # record it, because it may change when visiting children
+        super().visit_ArgumentNode(node)
+
+        for colon in node.colons:
+            self.add_space_after(colon)
+
+        if self.config.wide_colon:
+            for key in node.kwargs:
+                self.add_space_after(key)
+
+        arguments_count = len(node.arguments) + len(node.kwargs)
+        has_trailing_comma = node.commas and len(node.commas) == arguments_count
+        if node.is_multiline:
+            need_comma = True
+            if arguments_count == 1 and is_function_arguments:
+                need_comma = not self.config.no_single_comma_function
+
+            if need_comma and not has_trailing_comma:
+                comma = mparser.SymbolNode(mparser.Token('comma', node.filename, 0, 0, 0, (0, 0), ','))
+                comma.condition_level = node.condition_level
+                node.commas.append(comma)
+            elif has_trailing_comma and not need_comma:
+                node.commas.pop(-1)
+
+            arg_index = 0
+            if self.config.group_arg_value:
+                for arg in node.arguments[:-1]:
+                    group_args = False
+                    if isinstance(arg, mparser.StringNode) and arg.value.startswith('--'):
+                        next_arg = node.arguments[arg_index + 1]
+                        if isinstance(next_arg, mparser.StringNode) and not next_arg.value.startswith('--'):
+                            group_args = True
+                    if group_args:
+                        # keep '--arg', 'value' on same line
+                        self.add_space_after(node.commas[arg_index])
+                    elif arg_index < len(node.commas):
+                        self.add_nl_after(node.commas[arg_index], self.level)
+                    arg_index += 1
+
+            for comma in node.commas[arg_index:-1]:
+                self.add_nl_after(comma, self.level)
+            self.add_nl_after(node, self.level - 1)
+
+        else:
+            if has_trailing_comma and not (node.commas[-1].whitespaces and node.commas[-1].whitespaces.value):
+                node.commas.pop(-1)
+
+            for comma in node.commas:
+                self.add_space_after(comma)
+
+        self.exit_node(node)
+
+    def visit_ParenthesizedNode(self, node: mparser.ParenthesizedNode) -> None:
+        self.enter_node(node)
+        is_multiline = '\n' in node.lpar.whitespaces.value
+        if is_multiline:
+            current_indent_after = self.indent_after
+            self.indent_after = True
+        node.lpar.accept(self)
+        node.inner.accept(self)
+        if is_multiline:
+            self.indent_after = current_indent_after
+        node.rpar.accept(self)
+        self.exit_node(node)
+
+
+class ComputeLineLengths(FullAstVisitor):
+
+    def __init__(self, config: FormatterConfig, level: int):
+        self.config = config
+        self.lengths: T.List[int] = []
+        self.length = 0
+        self.argument_stack: T.List[mparser.ArgumentNode] = []
+        self.level = level
+        self.need_regenerate = False
+
+    def visit_default_func(self, node: mparser.BaseNode) -> None:
+        self.enter_node(node)
+        assert hasattr(node, 'value')
+        self.length += len(str(node.value))
+        self.exit_node(node)
+
+    def len(self, line: str) -> int:
+        '''Compute line length, including tab stops'''
+        parts = line.split('\t')
+        line_length = len(parts[0])
+        for p in parts[1:]:
+            tab_length = ((self.length + line_length) % self.config.tab_width) or self.config.tab_width
+            line_length += tab_length + len(p)
+        return line_length
+
+    def count_multiline(self, value: str) -> None:
+        lines = value.splitlines(keepends=True)
+        for line in lines:
+            if line.endswith('\n'):
+                self.lengths.append(self.length + self.len(line) - 1)
+                self.length = 0
+            else:
+                self.length += self.len(line)
+
+    def visit_WhitespaceNode(self, node: mparser.WhitespaceNode) -> None:
+        self.count_multiline(node.value)
+
+    def visit_EmptyNode(self, node: mparser.EmptyNode) -> None:
+        self.enter_node(node)
+        self.exit_node(node)
+
+    def visit_NumberNode(self, node: mparser.NumberNode) -> None:
+        self.enter_node(node)
+        self.length += len(node.raw_value)
+        self.exit_node(node)
+
+    def visit_StringNode(self, node: mparser.StringNode) -> None:
+        self.enter_node(node)
+        if node.is_fstring:
+            self.length += 1
+
+        if node.is_multiline:
+            self.length += 3
+            self.count_multiline(node.value)
+            self.length += 3
+        else:
+            self.length += self.len(node.raw_value) + 2
+
+        self.exit_node(node)
+
+    def visit_ContinueNode(self, node: mparser.ContinueNode) -> None:
+        self.enter_node(node)
+        self.length += len('continue')
+        self.exit_node(node)
+
+    def visit_BreakNode(self, node: mparser.BreakNode) -> None:
+        self.enter_node(node)
+        self.length += len('break')
+        self.exit_node(node)
+
+    def split_if_needed(self, node: mparser.ArgumentNode) -> None:
+        if not node.is_multiline and self.length > self.config.max_line_length:
+            arg = self.argument_stack[self.level] if len(self.argument_stack) > self.level else node
+            if not arg.is_multiline:
+                arg.is_multiline = True
+                self.need_regenerate = True
+
+    def visit_ArgumentNode(self, node: mparser.ArgumentNode) -> None:
+        self.argument_stack.append(node)
+        super().visit_ArgumentNode(node)
+        self.split_if_needed(node)
+        self.argument_stack.pop(-1)
+
+    def visit_ArrayNode(self, node: mparser.ArrayNode) -> None:
+        self.enter_node(node)
+        node.lbracket.accept(self)
+        node.args.accept(self)
+        node.rbracket.accept(self)
+        self.split_if_needed(node.args)  # split if closing bracket is too far
+        self.exit_node(node)
+
+    def visit_DictNode(self, node: mparser.DictNode) -> None:
+        self.enter_node(node)
+        node.lcurl.accept(self)
+        node.args.accept(self)
+        node.rcurl.accept(self)
+        self.split_if_needed(node.args)  # split if closing bracket is too far
+        self.exit_node(node)
+
+
+class SubdirFetcher(FullAstVisitor):
+
+    def __init__(self, current_dir: Path):
+        self.current_dir = current_dir
+        self.subdirs: T.List[Path] = []
+
+    def visit_FunctionNode(self, node: mparser.FunctionNode) -> None:
+        if node.func_name.value == 'subdir':
+            if node.args.arguments and isinstance(node.args.arguments[0], mparser.StringNode):
+                subdir = node.args.arguments[0].value
+                self.subdirs.append(self.current_dir / subdir)
+        super().visit_FunctionNode(node)
+
+
+class Formatter:
+
+    def __init__(self, configuration_file: T.Optional[Path], use_editor_config: bool, fetch_subdirs: bool):
+        self.fetch_subdirs = fetch_subdirs
+        self.use_editor_config = use_editor_config
+        self.config = self.load_configuration(configuration_file)
+        self.current_config = self.config
+
+        self.current_dir = Path()
+        self.subdirs: T.List[Path] = []
+
+    def load_editor_config(self, source_file: Path) -> EditorConfig:
+        # See https://editorconfig.org/
+        config = EditorConfig()
+
+        for p in source_file.parents:
+            editorconfig_file = p / '.editorconfig'
+            if not editorconfig_file.exists():
+                continue
+
+            cp = DefaultConfigParser(delimiters=('=',))
+            cp.read_default(editorconfig_file)
+
+            sections = [section for section in cp.sections() if match_path(source_file.as_posix(), section)]
+            for f in fields(config):
+                if getattr(cp, f.name, None) is not None:
+                    continue  # value already set from higher file
+
+                getter = f.metadata['getter']
+                for section in sections:
+                    value = getter(cp, section, f.name, fallback=None)
+                    if value is not None:
+                        setattr(config, f.name, value)
+
+            if cp.getboolean(cp.default_section, 'root'):
+                break
+
+        return config
+
+    def load_configuration(self, configuration_file: T.Optional[Path]) -> FormatterConfig:
+        config = FormatterConfig()
+        if configuration_file:
+            cp = DefaultConfigParser()
+            cp.read_default(configuration_file)
+
+            for f in fields(config):
+                getter = f.metadata['getter']
+                value = getter(cp, cp.default_section, f.name, fallback=None)
+                if value is not None:
+                    setattr(config, f.name, value)
+
+            if config.use_editor_config:
+                self.use_editor_config = True
+
+        return config
+
+    def format(self, code: str, source_file: Path) -> str:
+        self.current_dir = source_file.parent
+        self.current_config = FormatterConfig.default()
+        if self.use_editor_config:
+            self.current_config = self.current_config.with_editorconfig(self.load_editor_config(source_file))
+        self.current_config = self.current_config.update(self.config)
+
+        ast = mparser.Parser(code, source_file.as_posix()).parse()
+        if self.fetch_subdirs:
+            subdir_fetcher = SubdirFetcher(self.current_dir)
+            ast.accept(subdir_fetcher)
+            self.subdirs = subdir_fetcher.subdirs
+
+        ast.accept(AstConditionLevel())
+        for level in range(5):
+            ast.accept(TrimWhitespaces(self.current_config))
+            ast.accept(ArgumentFormatter(self.current_config))
+
+            cll = ComputeLineLengths(self.current_config, level)
+            ast.accept(cll)
+            if not cll.need_regenerate:
+                break
+
+        printer = RawPrinter()
+        ast.accept(printer)
+        return printer.result
+
+
+def add_arguments(parser: argparse.ArgumentParser) -> None:
+    inplace_group = parser.add_mutually_exclusive_group()
+    inplace_group.add_argument(
+        '-q', '--check-only',
+        action='store_true',
+        help='exit with 1 if files would be modified by meson format'
+    )
+    inplace_group.add_argument(
+        '-i', '--inplace',
+        action='store_true',
+        help='format files in-place'
+    )
+    parser.add_argument(
+        '-r', '--recursive',
+        action='store_true',
+        help='recurse subdirs (requires --check-only or --inplace option)',
+    )
+    parser.add_argument(
+        '-c', '--configuration',
+        metavar='meson.format',
+        type=Path,
+        help='read configuration from meson.format'
+    )
+    parser.add_argument(
+        '-e', '--editor-config',
+        action='store_true',
+        default=False,
+        help='try to read configuration from .editorconfig'
+    )
+    parser.add_argument(
+        '-o', '--output',
+        type=Path,
+        help='output file (implies having exactly one input)'
+    )
+    parser.add_argument(
+        'sources',
+        nargs='*',
+        type=Path,
+        help='meson source files'
+    )
+
+def run(options: argparse.Namespace) -> int:
+    if options.output and len(options.sources) != 1:
+        raise MesonException('--output argument implies having exactly one source file')
+    if options.recursive and not (options.inplace or options.check_only):
+        raise MesonException('--recursive argument requires either --inplace or --check-only option')
+
+    sources: T.List[Path] = options.sources.copy() or [Path(build_filename)]
+    if not options.configuration:
+        default_config_path = sources[0].parent / 'meson.format'
+        if default_config_path.exists():
+            options.configuration = default_config_path
+    formatter = Formatter(options.configuration, options.editor_config, options.recursive)
+
+    while sources:
+        src_file = sources.pop(0)
+        if src_file.is_dir():
+            src_file = src_file / build_filename
+
+        try:
+            code = src_file.read_text(encoding='utf-8')
+        except IOError as e:
+            raise MesonException(f'Unable to read from {src_file}') from e
+
+        formatted = formatter.format(code, src_file)
+        if options.recursive:
+            sources.extend(formatter.subdirs)
+
+        if options.inplace:
+            try:
+                with src_file.open('w', encoding='utf-8', newline=formatter.current_config.newline) as sf:
+                    sf.write(formatted)
+            except IOError as e:
+                raise MesonException(f'Unable to write to {src_file}') from e
+        elif options.check_only:
+            # TODO: add verbose output showing diffs
+            if code != formatted:
+                return 1
+        elif options.output:
+            try:
+                with options.output.open('w', encoding='utf-8', newline=formatter.current_config.newline) as of:
+                    of.write(formatted)
+            except IOError as e:
+                raise MesonException(f'Unable to write to {src_file}') from e
+        else:
+            print(formatted, end='')
+
+    return 0
+
+# TODO: remove empty newlines when more than N (2...)
+# TODO: magic comment to prevent formatting
+# TODO: handle meson.options ?
+# TODO: split long lines on binary operators
+# TODO: align series of assignements
+# TODO: align comments
+# TODO: move comments on long lines
+
+# Differences from muon format:
+# - By default, uses two spaces before comment, and added option for that
+# - Muon will mix CRLF and LF on Windows files...
+# - Support for end_of_line char
+# - Support for max_line_length, end_of_line, insert_final_newline, tab_width in .editorconfig
+# - Option to simplify string literals
+# - Option to recognize and parse meson.build in subdirs
+# - Correctly compute line length when using tabs
+# - By default, arguments in files() are sorted alphabetically
+# - Option to group '--arg', 'value' on same line in multiline arguments
diff --git a/mesonbuild/mparser.py b/mesonbuild/mparser.py
index 0e26b9ed9..ec08ccfb2 100644
--- a/mesonbuild/mparser.py
+++ b/mesonbuild/mparser.py
@@ -343,6 +343,9 @@ class ArgumentNode(BaseNode):
         self.kwargs = {}
         self.order_error = False
 
+        # Attributes for the visitors
+        self.is_multiline = False
+
     def prepend(self, statement: BaseNode) -> None:
         if self.num_kwargs() > 0:
             self.order_error = True