Compare formatted and unformatted ASTs during formatter tests (#8624)

## Summary

This PR implements validation in the formatter tests to ensure that we
don't modify the AST during formatting. Black has similar logic.

In implementing this, I learned that Black actually _does_ modify the
AST, and their test infrastructure normalizes the AST to wipe away those
differences. Specifically, Black changes the indentation of docstrings,
which _does_ modify the AST; and it also inserts parentheses in `del`
statements, which changes the AST too.

Ruff also does both these things, so we _also_ implement the same
normalization using a new visitor that allows for modifying the AST.

Closes https://github.com/astral-sh/ruff/issues/8184.

## Test Plan

`cargo test`
This commit is contained in:
Charlie Marsh 2023-11-13 09:43:27 -08:00 committed by GitHub
parent 3592f44ade
commit d574fcd1ac
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
5 changed files with 930 additions and 19 deletions

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@ -1480,3 +1480,44 @@ impl<'a> From<&'a ast::Stmt> for ComparableStmt<'a> {
}
}
}
#[derive(Debug, PartialEq, Eq, Hash)]
pub enum ComparableMod<'a> {
Module(ComparableModModule<'a>),
Expression(ComparableModExpression<'a>),
}
#[derive(Debug, PartialEq, Eq, Hash)]
pub struct ComparableModModule<'a> {
body: Vec<ComparableStmt<'a>>,
}
#[derive(Debug, PartialEq, Eq, Hash)]
pub struct ComparableModExpression<'a> {
body: Box<ComparableExpr<'a>>,
}
impl<'a> From<&'a ast::Mod> for ComparableMod<'a> {
fn from(mod_: &'a ast::Mod) -> Self {
match mod_ {
ast::Mod::Module(module) => Self::Module(module.into()),
ast::Mod::Expression(expr) => Self::Expression(expr.into()),
}
}
}
impl<'a> From<&'a ast::ModModule> for ComparableModModule<'a> {
fn from(module: &'a ast::ModModule) -> Self {
Self {
body: module.body.iter().map(Into::into).collect(),
}
}
}
impl<'a> From<&'a ast::ModExpression> for ComparableModExpression<'a> {
fn from(expr: &'a ast::ModExpression) -> Self {
Self {
body: (&expr.body).into(),
}
}
}

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@ -1,6 +1,7 @@
//! AST visitor trait and walk functions.
pub mod preorder;
pub mod transformer;
use crate::{
self as ast, Alias, Arguments, BoolOp, CmpOp, Comprehension, Decorator, ElifElseClause,
@ -14,8 +15,10 @@ use crate::{
/// Prefer [`crate::statement_visitor::StatementVisitor`] for visitors that only need to visit
/// statements.
///
/// Use the [`PreorderVisitor`](self::preorder::PreorderVisitor) if you want to visit the nodes
/// Use the [`PreorderVisitor`](preorder::PreorderVisitor) if you want to visit the nodes
/// in pre-order rather than evaluation order.
///
/// Use the [`Transformer`](transformer::Transformer) if you want to modify the nodes.
pub trait Visitor<'a> {
fn visit_stmt(&mut self, stmt: &'a Stmt) {
walk_stmt(self, stmt);

View file

@ -0,0 +1,732 @@
use crate::{
self as ast, Alias, Arguments, BoolOp, CmpOp, Comprehension, Decorator, ElifElseClause,
ExceptHandler, Expr, ExprContext, Keyword, MatchCase, Operator, Parameter, Parameters, Pattern,
PatternArguments, PatternKeyword, Stmt, TypeParam, TypeParamTypeVar, TypeParams, UnaryOp,
WithItem,
};
/// A trait for transforming ASTs. Visits all nodes in the AST recursively in evaluation-order.
pub trait Transformer {
fn visit_stmt(&self, stmt: &mut Stmt) {
walk_stmt(self, stmt);
}
fn visit_annotation(&self, expr: &mut Expr) {
walk_annotation(self, expr);
}
fn visit_decorator(&self, decorator: &mut Decorator) {
walk_decorator(self, decorator);
}
fn visit_expr(&self, expr: &mut Expr) {
walk_expr(self, expr);
}
fn visit_expr_context(&self, expr_context: &mut ExprContext) {
walk_expr_context(self, expr_context);
}
fn visit_bool_op(&self, bool_op: &mut BoolOp) {
walk_bool_op(self, bool_op);
}
fn visit_operator(&self, operator: &mut Operator) {
walk_operator(self, operator);
}
fn visit_unary_op(&self, unary_op: &mut UnaryOp) {
walk_unary_op(self, unary_op);
}
fn visit_cmp_op(&self, cmp_op: &mut CmpOp) {
walk_cmp_op(self, cmp_op);
}
fn visit_comprehension(&self, comprehension: &mut Comprehension) {
walk_comprehension(self, comprehension);
}
fn visit_except_handler(&self, except_handler: &mut ExceptHandler) {
walk_except_handler(self, except_handler);
}
fn visit_format_spec(&self, format_spec: &mut Expr) {
walk_format_spec(self, format_spec);
}
fn visit_arguments(&self, arguments: &mut Arguments) {
walk_arguments(self, arguments);
}
fn visit_parameters(&self, parameters: &mut Parameters) {
walk_parameters(self, parameters);
}
fn visit_parameter(&self, parameter: &mut Parameter) {
walk_parameter(self, parameter);
}
fn visit_keyword(&self, keyword: &mut Keyword) {
walk_keyword(self, keyword);
}
fn visit_alias(&self, alias: &mut Alias) {
walk_alias(self, alias);
}
fn visit_with_item(&self, with_item: &mut WithItem) {
walk_with_item(self, with_item);
}
fn visit_type_params(&self, type_params: &mut TypeParams) {
walk_type_params(self, type_params);
}
fn visit_type_param(&self, type_param: &mut TypeParam) {
walk_type_param(self, type_param);
}
fn visit_match_case(&self, match_case: &mut MatchCase) {
walk_match_case(self, match_case);
}
fn visit_pattern(&self, pattern: &mut Pattern) {
walk_pattern(self, pattern);
}
fn visit_pattern_arguments(&self, pattern_arguments: &mut PatternArguments) {
walk_pattern_arguments(self, pattern_arguments);
}
fn visit_pattern_keyword(&self, pattern_keyword: &mut PatternKeyword) {
walk_pattern_keyword(self, pattern_keyword);
}
fn visit_body(&self, body: &mut [Stmt]) {
walk_body(self, body);
}
fn visit_elif_else_clause(&self, elif_else_clause: &mut ElifElseClause) {
walk_elif_else_clause(self, elif_else_clause);
}
}
pub fn walk_body<V: Transformer + ?Sized>(visitor: &V, body: &mut [Stmt]) {
for stmt in body {
visitor.visit_stmt(stmt);
}
}
pub fn walk_elif_else_clause<V: Transformer + ?Sized>(
visitor: &V,
elif_else_clause: &mut ElifElseClause,
) {
if let Some(test) = &mut elif_else_clause.test {
visitor.visit_expr(test);
}
visitor.visit_body(&mut elif_else_clause.body);
}
pub fn walk_stmt<V: Transformer + ?Sized>(visitor: &V, stmt: &mut Stmt) {
match stmt {
Stmt::FunctionDef(ast::StmtFunctionDef {
parameters,
body,
decorator_list,
returns,
type_params,
..
}) => {
for decorator in decorator_list {
visitor.visit_decorator(decorator);
}
if let Some(type_params) = type_params {
visitor.visit_type_params(type_params);
}
visitor.visit_parameters(parameters);
for expr in returns {
visitor.visit_annotation(expr);
}
visitor.visit_body(body);
}
Stmt::ClassDef(ast::StmtClassDef {
arguments,
body,
decorator_list,
type_params,
..
}) => {
for decorator in decorator_list {
visitor.visit_decorator(decorator);
}
if let Some(type_params) = type_params {
visitor.visit_type_params(type_params);
}
if let Some(arguments) = arguments {
visitor.visit_arguments(arguments);
}
visitor.visit_body(body);
}
Stmt::Return(ast::StmtReturn { value, range: _ }) => {
if let Some(expr) = value {
visitor.visit_expr(expr);
}
}
Stmt::Delete(ast::StmtDelete { targets, range: _ }) => {
for expr in targets {
visitor.visit_expr(expr);
}
}
Stmt::TypeAlias(ast::StmtTypeAlias {
range: _,
name,
type_params,
value,
}) => {
visitor.visit_expr(value);
if let Some(type_params) = type_params {
visitor.visit_type_params(type_params);
}
visitor.visit_expr(name);
}
Stmt::Assign(ast::StmtAssign { targets, value, .. }) => {
visitor.visit_expr(value);
for expr in targets {
visitor.visit_expr(expr);
}
}
Stmt::AugAssign(ast::StmtAugAssign {
target,
op,
value,
range: _,
}) => {
visitor.visit_expr(value);
visitor.visit_operator(op);
visitor.visit_expr(target);
}
Stmt::AnnAssign(ast::StmtAnnAssign {
target,
annotation,
value,
..
}) => {
if let Some(expr) = value {
visitor.visit_expr(expr);
}
visitor.visit_annotation(annotation);
visitor.visit_expr(target);
}
Stmt::For(ast::StmtFor {
target,
iter,
body,
orelse,
..
}) => {
visitor.visit_expr(iter);
visitor.visit_expr(target);
visitor.visit_body(body);
visitor.visit_body(orelse);
}
Stmt::While(ast::StmtWhile {
test,
body,
orelse,
range: _,
}) => {
visitor.visit_expr(test);
visitor.visit_body(body);
visitor.visit_body(orelse);
}
Stmt::If(ast::StmtIf {
test,
body,
elif_else_clauses,
range: _,
}) => {
visitor.visit_expr(test);
visitor.visit_body(body);
for clause in elif_else_clauses {
if let Some(test) = &mut clause.test {
visitor.visit_expr(test);
}
walk_elif_else_clause(visitor, clause);
}
}
Stmt::With(ast::StmtWith { items, body, .. }) => {
for with_item in items {
visitor.visit_with_item(with_item);
}
visitor.visit_body(body);
}
Stmt::Match(ast::StmtMatch {
subject,
cases,
range: _,
}) => {
visitor.visit_expr(subject);
for match_case in cases {
visitor.visit_match_case(match_case);
}
}
Stmt::Raise(ast::StmtRaise {
exc,
cause,
range: _,
}) => {
if let Some(expr) = exc {
visitor.visit_expr(expr);
};
if let Some(expr) = cause {
visitor.visit_expr(expr);
};
}
Stmt::Try(ast::StmtTry {
body,
handlers,
orelse,
finalbody,
is_star: _,
range: _,
}) => {
visitor.visit_body(body);
for except_handler in handlers {
visitor.visit_except_handler(except_handler);
}
visitor.visit_body(orelse);
visitor.visit_body(finalbody);
}
Stmt::Assert(ast::StmtAssert {
test,
msg,
range: _,
}) => {
visitor.visit_expr(test);
if let Some(expr) = msg {
visitor.visit_expr(expr);
}
}
Stmt::Import(ast::StmtImport { names, range: _ }) => {
for alias in names {
visitor.visit_alias(alias);
}
}
Stmt::ImportFrom(ast::StmtImportFrom { names, .. }) => {
for alias in names {
visitor.visit_alias(alias);
}
}
Stmt::Global(_) => {}
Stmt::Nonlocal(_) => {}
Stmt::Expr(ast::StmtExpr { value, range: _ }) => visitor.visit_expr(value),
Stmt::Pass(_) | Stmt::Break(_) | Stmt::Continue(_) | Stmt::IpyEscapeCommand(_) => {}
}
}
pub fn walk_annotation<V: Transformer + ?Sized>(visitor: &V, expr: &mut Expr) {
visitor.visit_expr(expr);
}
pub fn walk_decorator<V: Transformer + ?Sized>(visitor: &V, decorator: &mut Decorator) {
visitor.visit_expr(&mut decorator.expression);
}
pub fn walk_expr<V: Transformer + ?Sized>(visitor: &V, expr: &mut Expr) {
match expr {
Expr::BoolOp(ast::ExprBoolOp {
op,
values,
range: _,
}) => {
visitor.visit_bool_op(op);
for expr in values {
visitor.visit_expr(expr);
}
}
Expr::NamedExpr(ast::ExprNamedExpr {
target,
value,
range: _,
}) => {
visitor.visit_expr(value);
visitor.visit_expr(target);
}
Expr::BinOp(ast::ExprBinOp {
left,
op,
right,
range: _,
}) => {
visitor.visit_expr(left);
visitor.visit_operator(op);
visitor.visit_expr(right);
}
Expr::UnaryOp(ast::ExprUnaryOp {
op,
operand,
range: _,
}) => {
visitor.visit_unary_op(op);
visitor.visit_expr(operand);
}
Expr::Lambda(ast::ExprLambda {
parameters,
body,
range: _,
}) => {
if let Some(parameters) = parameters {
visitor.visit_parameters(parameters);
}
visitor.visit_expr(body);
}
Expr::IfExp(ast::ExprIfExp {
test,
body,
orelse,
range: _,
}) => {
visitor.visit_expr(test);
visitor.visit_expr(body);
visitor.visit_expr(orelse);
}
Expr::Dict(ast::ExprDict {
keys,
values,
range: _,
}) => {
for expr in keys.iter_mut().flatten() {
visitor.visit_expr(expr);
}
for expr in values {
visitor.visit_expr(expr);
}
}
Expr::Set(ast::ExprSet { elts, range: _ }) => {
for expr in elts {
visitor.visit_expr(expr);
}
}
Expr::ListComp(ast::ExprListComp {
elt,
generators,
range: _,
}) => {
for comprehension in generators {
visitor.visit_comprehension(comprehension);
}
visitor.visit_expr(elt);
}
Expr::SetComp(ast::ExprSetComp {
elt,
generators,
range: _,
}) => {
for comprehension in generators {
visitor.visit_comprehension(comprehension);
}
visitor.visit_expr(elt);
}
Expr::DictComp(ast::ExprDictComp {
key,
value,
generators,
range: _,
}) => {
for comprehension in generators {
visitor.visit_comprehension(comprehension);
}
visitor.visit_expr(key);
visitor.visit_expr(value);
}
Expr::GeneratorExp(ast::ExprGeneratorExp {
elt,
generators,
range: _,
}) => {
for comprehension in generators {
visitor.visit_comprehension(comprehension);
}
visitor.visit_expr(elt);
}
Expr::Await(ast::ExprAwait { value, range: _ }) => visitor.visit_expr(value),
Expr::Yield(ast::ExprYield { value, range: _ }) => {
if let Some(expr) = value {
visitor.visit_expr(expr);
}
}
Expr::YieldFrom(ast::ExprYieldFrom { value, range: _ }) => visitor.visit_expr(value),
Expr::Compare(ast::ExprCompare {
left,
ops,
comparators,
range: _,
}) => {
visitor.visit_expr(left);
for cmp_op in ops {
visitor.visit_cmp_op(cmp_op);
}
for expr in comparators {
visitor.visit_expr(expr);
}
}
Expr::Call(ast::ExprCall {
func,
arguments,
range: _,
}) => {
visitor.visit_expr(func);
visitor.visit_arguments(arguments);
}
Expr::FormattedValue(ast::ExprFormattedValue {
value, format_spec, ..
}) => {
visitor.visit_expr(value);
if let Some(expr) = format_spec {
visitor.visit_format_spec(expr);
}
}
Expr::FString(ast::ExprFString { values, .. }) => {
for expr in values {
visitor.visit_expr(expr);
}
}
Expr::StringLiteral(_)
| Expr::BytesLiteral(_)
| Expr::NumberLiteral(_)
| Expr::BooleanLiteral(_)
| Expr::NoneLiteral(_)
| Expr::EllipsisLiteral(_) => {}
Expr::Attribute(ast::ExprAttribute { value, ctx, .. }) => {
visitor.visit_expr(value);
visitor.visit_expr_context(ctx);
}
Expr::Subscript(ast::ExprSubscript {
value,
slice,
ctx,
range: _,
}) => {
visitor.visit_expr(value);
visitor.visit_expr(slice);
visitor.visit_expr_context(ctx);
}
Expr::Starred(ast::ExprStarred {
value,
ctx,
range: _,
}) => {
visitor.visit_expr(value);
visitor.visit_expr_context(ctx);
}
Expr::Name(ast::ExprName { ctx, .. }) => {
visitor.visit_expr_context(ctx);
}
Expr::List(ast::ExprList {
elts,
ctx,
range: _,
}) => {
for expr in elts {
visitor.visit_expr(expr);
}
visitor.visit_expr_context(ctx);
}
Expr::Tuple(ast::ExprTuple {
elts,
ctx,
range: _,
}) => {
for expr in elts {
visitor.visit_expr(expr);
}
visitor.visit_expr_context(ctx);
}
Expr::Slice(ast::ExprSlice {
lower,
upper,
step,
range: _,
}) => {
if let Some(expr) = lower {
visitor.visit_expr(expr);
}
if let Some(expr) = upper {
visitor.visit_expr(expr);
}
if let Some(expr) = step {
visitor.visit_expr(expr);
}
}
Expr::IpyEscapeCommand(_) => {}
}
}
pub fn walk_comprehension<V: Transformer + ?Sized>(visitor: &V, comprehension: &mut Comprehension) {
visitor.visit_expr(&mut comprehension.iter);
visitor.visit_expr(&mut comprehension.target);
for expr in &mut comprehension.ifs {
visitor.visit_expr(expr);
}
}
pub fn walk_except_handler<V: Transformer + ?Sized>(
visitor: &V,
except_handler: &mut ExceptHandler,
) {
match except_handler {
ExceptHandler::ExceptHandler(ast::ExceptHandlerExceptHandler { type_, body, .. }) => {
if let Some(expr) = type_ {
visitor.visit_expr(expr);
}
visitor.visit_body(body);
}
}
}
pub fn walk_format_spec<V: Transformer + ?Sized>(visitor: &V, format_spec: &mut Expr) {
visitor.visit_expr(format_spec);
}
pub fn walk_arguments<V: Transformer + ?Sized>(visitor: &V, arguments: &mut Arguments) {
// Note that the there might be keywords before the last arg, e.g. in
// f(*args, a=2, *args2, **kwargs)`, but we follow Python in evaluating first `args` and then
// `keywords`. See also [Arguments::arguments_source_order`].
for arg in &mut arguments.args {
visitor.visit_expr(arg);
}
for keyword in &mut arguments.keywords {
visitor.visit_keyword(keyword);
}
}
pub fn walk_parameters<V: Transformer + ?Sized>(visitor: &V, parameters: &mut Parameters) {
// Defaults are evaluated before annotations.
for arg in &mut parameters.posonlyargs {
if let Some(default) = &mut arg.default {
visitor.visit_expr(default);
}
}
for arg in &mut parameters.args {
if let Some(default) = &mut arg.default {
visitor.visit_expr(default);
}
}
for arg in &mut parameters.kwonlyargs {
if let Some(default) = &mut arg.default {
visitor.visit_expr(default);
}
}
for arg in &mut parameters.posonlyargs {
visitor.visit_parameter(&mut arg.parameter);
}
for arg in &mut parameters.args {
visitor.visit_parameter(&mut arg.parameter);
}
if let Some(arg) = &mut parameters.vararg {
visitor.visit_parameter(arg);
}
for arg in &mut parameters.kwonlyargs {
visitor.visit_parameter(&mut arg.parameter);
}
if let Some(arg) = &mut parameters.kwarg {
visitor.visit_parameter(arg);
}
}
pub fn walk_parameter<V: Transformer + ?Sized>(visitor: &V, parameter: &mut Parameter) {
if let Some(expr) = &mut parameter.annotation {
visitor.visit_annotation(expr);
}
}
pub fn walk_keyword<V: Transformer + ?Sized>(visitor: &V, keyword: &mut Keyword) {
visitor.visit_expr(&mut keyword.value);
}
pub fn walk_with_item<V: Transformer + ?Sized>(visitor: &V, with_item: &mut WithItem) {
visitor.visit_expr(&mut with_item.context_expr);
if let Some(expr) = &mut with_item.optional_vars {
visitor.visit_expr(expr);
}
}
pub fn walk_type_params<V: Transformer + ?Sized>(visitor: &V, type_params: &mut TypeParams) {
for type_param in &mut type_params.type_params {
visitor.visit_type_param(type_param);
}
}
pub fn walk_type_param<V: Transformer + ?Sized>(visitor: &V, type_param: &mut TypeParam) {
match type_param {
TypeParam::TypeVar(TypeParamTypeVar {
bound,
name: _,
range: _,
}) => {
if let Some(expr) = bound {
visitor.visit_expr(expr);
}
}
TypeParam::TypeVarTuple(_) | TypeParam::ParamSpec(_) => {}
}
}
pub fn walk_match_case<V: Transformer + ?Sized>(visitor: &V, match_case: &mut MatchCase) {
visitor.visit_pattern(&mut match_case.pattern);
if let Some(expr) = &mut match_case.guard {
visitor.visit_expr(expr);
}
visitor.visit_body(&mut match_case.body);
}
pub fn walk_pattern<V: Transformer + ?Sized>(visitor: &V, pattern: &mut Pattern) {
match pattern {
Pattern::MatchValue(ast::PatternMatchValue { value, .. }) => {
visitor.visit_expr(value);
}
Pattern::MatchSingleton(_) => {}
Pattern::MatchSequence(ast::PatternMatchSequence { patterns, .. }) => {
for pattern in patterns {
visitor.visit_pattern(pattern);
}
}
Pattern::MatchMapping(ast::PatternMatchMapping { keys, patterns, .. }) => {
for expr in keys {
visitor.visit_expr(expr);
}
for pattern in patterns {
visitor.visit_pattern(pattern);
}
}
Pattern::MatchClass(ast::PatternMatchClass { cls, arguments, .. }) => {
visitor.visit_expr(cls);
visitor.visit_pattern_arguments(arguments);
}
Pattern::MatchStar(_) => {}
Pattern::MatchAs(ast::PatternMatchAs { pattern, .. }) => {
if let Some(pattern) = pattern {
visitor.visit_pattern(pattern);
}
}
Pattern::MatchOr(ast::PatternMatchOr { patterns, .. }) => {
for pattern in patterns {
visitor.visit_pattern(pattern);
}
}
}
}
pub fn walk_pattern_arguments<V: Transformer + ?Sized>(
visitor: &V,
pattern_arguments: &mut PatternArguments,
) {
for pattern in &mut pattern_arguments.patterns {
visitor.visit_pattern(pattern);
}
for keyword in &mut pattern_arguments.keywords {
visitor.visit_pattern_keyword(keyword);
}
}
pub fn walk_pattern_keyword<V: Transformer + ?Sized>(
visitor: &V,
pattern_keyword: &mut PatternKeyword,
) {
visitor.visit_pattern(&mut pattern_keyword.pattern);
}
#[allow(unused_variables)]
pub fn walk_expr_context<V: Transformer + ?Sized>(visitor: &V, expr_context: &mut ExprContext) {}
#[allow(unused_variables)]
pub fn walk_bool_op<V: Transformer + ?Sized>(visitor: &V, bool_op: &mut BoolOp) {}
#[allow(unused_variables)]
pub fn walk_operator<V: Transformer + ?Sized>(visitor: &V, operator: &mut Operator) {}
#[allow(unused_variables)]
pub fn walk_unary_op<V: Transformer + ?Sized>(visitor: &V, unary_op: &mut UnaryOp) {}
#[allow(unused_variables)]
pub fn walk_cmp_op<V: Transformer + ?Sized>(visitor: &V, cmp_op: &mut CmpOp) {}
#[allow(unused_variables)]
pub fn walk_alias<V: Transformer + ?Sized>(visitor: &V, alias: &mut Alias) {}

View file

@ -1,11 +1,18 @@
use ruff_formatter::FormatOptions;
use ruff_python_formatter::{format_module_source, PreviewMode, PyFormatOptions};
use similar::TextDiff;
use std::fmt::{Formatter, Write};
use std::io::BufReader;
use std::path::Path;
use std::{fmt, fs};
use similar::TextDiff;
use crate::normalizer::Normalizer;
use ruff_formatter::FormatOptions;
use ruff_python_ast::comparable::ComparableMod;
use ruff_python_formatter::{format_module_source, PreviewMode, PyFormatOptions};
use ruff_python_parser::{parse, AsMode};
mod normalizer;
#[test]
fn black_compatibility() {
let test_file = |input_path: &Path| {
@ -33,6 +40,7 @@ fn black_compatibility() {
let formatted_code = printed.as_code();
ensure_unchanged_ast(&content, formatted_code, &options, input_path);
ensure_stability_when_formatting_twice(formatted_code, options, input_path);
if formatted_code == expected_output {
@ -111,6 +119,7 @@ fn format() {
format_module_source(&content, options.clone()).expect("Formatting to succeed");
let formatted_code = printed.as_code();
ensure_unchanged_ast(&content, formatted_code, &options, input_path);
ensure_stability_when_formatting_twice(formatted_code, options.clone(), input_path);
let mut snapshot = format!("## Input\n{}", CodeFrame::new("python", &content));
@ -128,6 +137,7 @@ fn format() {
format_module_source(&content, options.clone()).expect("Formatting to succeed");
let formatted_code = printed.as_code();
ensure_unchanged_ast(&content, formatted_code, &options, input_path);
ensure_stability_when_formatting_twice(formatted_code, options.clone(), input_path);
writeln!(
@ -140,29 +150,20 @@ fn format() {
.unwrap();
}
} else {
let printed =
format_module_source(&content, options.clone()).expect("Formatting to succeed");
let formatted = printed.as_code();
ensure_stability_when_formatting_twice(formatted, options.clone(), input_path);
// We want to capture the differences in the preview style in our fixtures
let options_preview = options.with_preview(PreviewMode::Enabled);
let printed_preview = format_module_source(&content, options_preview.clone())
.expect("Formatting to succeed");
let formatted_preview = printed_preview.as_code();
ensure_stability_when_formatting_twice(
formatted_preview,
options_preview.clone(),
input_path,
);
ensure_unchanged_ast(&content, formatted_preview, &options_preview, input_path);
ensure_stability_when_formatting_twice(formatted_preview, options_preview, input_path);
if formatted == formatted_preview {
if formatted_code == formatted_preview {
writeln!(
snapshot,
"## Output\n{}",
CodeFrame::new("python", &formatted)
CodeFrame::new("python", &formatted_code)
)
.unwrap();
} else {
@ -171,10 +172,10 @@ fn format() {
writeln!(
snapshot,
"## Output\n{}\n## Preview changes\n{}",
CodeFrame::new("python", &formatted),
CodeFrame::new("python", &formatted_code),
CodeFrame::new(
"diff",
TextDiff::from_lines(formatted, formatted_preview)
TextDiff::from_lines(formatted_code, formatted_preview)
.unified_diff()
.header("Stable", "Preview")
)
@ -239,6 +240,57 @@ Formatted twice:
}
}
/// Ensure that formatting doesn't change the AST.
///
/// Like Black, there are a few exceptions to this "invariant" which are encoded in
/// [`NormalizedMod`] and related structs. Namely, formatting can change indentation within strings,
/// and can also flatten tuples within `del` statements.
fn ensure_unchanged_ast(
unformatted_code: &str,
formatted_code: &str,
options: &PyFormatOptions,
input_path: &Path,
) {
let source_type = options.source_type();
// Parse the unformatted code.
let mut unformatted_ast = parse(
unformatted_code,
source_type.as_mode(),
&input_path.to_string_lossy(),
)
.expect("Unformatted code to be valid syntax");
Normalizer.visit_module(&mut unformatted_ast);
let unformatted_ast = ComparableMod::from(&unformatted_ast);
// Parse the formatted code.
let mut formatted_ast = parse(
formatted_code,
source_type.as_mode(),
&input_path.to_string_lossy(),
)
.expect("Formatted code to be valid syntax");
Normalizer.visit_module(&mut formatted_ast);
let formatted_ast = ComparableMod::from(&formatted_ast);
if formatted_ast != unformatted_ast {
let diff = TextDiff::from_lines(
&format!("{unformatted_ast:#?}"),
&format!("{formatted_ast:#?}"),
)
.unified_diff()
.header("Unformatted", "Formatted")
.to_string();
panic!(
r#"Reformatting the unformatted code of {} resulted in AST changes.
---
{diff}
"#,
input_path.display(),
);
}
}
struct Header<'a> {
title: &'a str,
}

View file

@ -0,0 +1,83 @@
use itertools::Either::{Left, Right};
use ruff_python_ast::visitor::transformer;
use ruff_python_ast::visitor::transformer::Transformer;
use ruff_python_ast::{self as ast, Expr, Stmt};
/// A struct to normalize AST nodes for the purpose of comparing formatted representations for
/// semantic equivalence.
///
/// Vis-à-vis comparing ASTs, comparing these normalized representations does the following:
/// - Ignores non-abstraction information that we've encoded into the AST, e.g., the difference
/// between `class C: ...` and `class C(): ...`, which is part of our AST but not `CPython`'s.
/// - Normalize strings. The formatter can re-indent docstrings, so we need to compare string
/// contents ignoring whitespace. (Black does the same.)
/// - Ignores nested tuples in deletions. (Black does the same.)
pub(crate) struct Normalizer;
impl Normalizer {
/// Transform an AST module into a normalized representation.
#[allow(dead_code)]
pub(crate) fn visit_module(&self, module: &mut ast::Mod) {
match module {
ast::Mod::Module(module) => {
self.visit_body(&mut module.body);
}
ast::Mod::Expression(expression) => {
self.visit_expr(&mut expression.body);
}
}
}
}
impl Transformer for Normalizer {
fn visit_stmt(&self, stmt: &mut Stmt) {
match stmt {
Stmt::ClassDef(class_def) => {
// Treat `class C: ...` and `class C(): ...` equivalently.
if class_def
.arguments
.as_ref()
.is_some_and(|arguments| arguments.is_empty())
{
class_def.arguments = None;
}
}
Stmt::Delete(delete) => {
// Treat `del a, b` and `del (a, b)` equivalently.
delete.targets = delete
.targets
.clone()
.into_iter()
.flat_map(|target| {
if let Expr::Tuple(tuple) = target {
Left(tuple.elts.into_iter())
} else {
Right(std::iter::once(target))
}
})
.collect();
}
_ => {}
}
transformer::walk_stmt(self, stmt);
}
fn visit_expr(&self, expr: &mut Expr) {
if let Expr::StringLiteral(string_literal) = expr {
// Normalize a string by (1) stripping any leading and trailing space from each
// line, and (2) removing any blank lines from the start and end of the string.
string_literal.value = string_literal
.value
.lines()
.map(str::trim)
.collect::<Vec<_>>()
.join("\n")
.trim()
.to_owned();
}
transformer::walk_expr(self, expr);
}
}