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Fix f-string format spec #3532

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Merged
merged 4 commits into from
Feb 10, 2022
Merged

Fix f-string format spec #3532

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04886d8
Allow brackets in f-string format spec
fanninpm Feb 2, 2022
a1dffe6
Allow replacement fields in format specs
fanninpm Feb 2, 2022
f2257a9
Allow proper recursion in f-string format specs
fanninpm Feb 2, 2022
a936c36
Add format-spec string test snippets
fanninpm Feb 2, 2022
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9 changes: 9 additions & 0 deletions extra_tests/snippets/fstrings.py
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,15 @@
spec = "0>+#10x"
assert f"{16:{spec}}{foo}" == '00000+0x10bar'

part_spec = ">+#10x"
assert f"{16:0{part_spec}}{foo}" == '00000+0x10bar'

# TODO: RUSTPYTHON, delete the next block once `test_fstring.py` can successfully parse
assert f'{10:#{1}0x}' == ' 0xa'
assert f'{10:{"#"}1{0}{"x"}}' == ' 0xa'
assert f'{-10:-{"#"}1{0}x}' == ' -0xa'
assert f'{-10:{"-"}#{1}0{"x"}}' == ' -0xa'

# TODO:
# spec = "bla"
# assert_raises(ValueError, lambda: f"{16:{spec}}")
Expand Down
97 changes: 60 additions & 37 deletions parser/src/fstring.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,13 +11,15 @@ use self::FStringErrorType::*;
struct FStringParser<'a> {
chars: iter::Peekable<str::Chars<'a>>,
str_location: Location,
recurse_lvl: u8,
}

impl<'a> FStringParser<'a> {
fn new(source: &'a str, str_location: Location) -> Self {
fn new(source: &'a str, str_location: Location, recurse_lvl: u8) -> Self {
Self {
chars: source.chars().peekable(),
str_location,
recurse_lvl,
}
}

Expand Down Expand Up @@ -91,52 +93,69 @@ impl<'a> FStringParser<'a> {
}

':' if delims.is_empty() => {
let mut nested = false;
let mut in_nested = false;
let mut spec_expression = String::new();
let mut spec_constructor = Vec::new();
let mut constant_piece = String::new();
let mut formatted_value_piece = String::new();
let mut spec_delims = Vec::new();
while let Some(&next) = self.chars.peek() {
match next {
'{' => {
if in_nested {
return Err(ExpressionNestedTooDeeply);
}
in_nested = true;
nested = true;
self.chars.next();
continue;
'{' if in_nested => {
spec_delims.push(next);
formatted_value_piece.push(next);
}
'}' => {
if in_nested {
'}' if in_nested => {
if spec_delims.is_empty() {
in_nested = false;
self.chars.next();
spec_constructor.push(
self.expr(ExprKind::FormattedValue {
value: Box::new(
FStringParser::new(
&format!("{{{}}}", formatted_value_piece),
Location::default(),
&self.recurse_lvl + 1,
)
.parse()?,
),
conversion: None,
format_spec: None,
}),
);
formatted_value_piece.clear();
} else {
spec_delims.pop();
formatted_value_piece.push(next);
}
break;
}
_ => (),
_ if in_nested => {
formatted_value_piece.push(next);
}
'{' => {
in_nested = true;
spec_constructor.push(self.expr(ExprKind::Constant {
value: constant_piece.to_owned().into(),
kind: None,
}));
constant_piece.clear();
}
'}' => break,
_ => {
constant_piece.push(next);
}
}
spec_expression.push(next);
self.chars.next();
}
spec_constructor.push(self.expr(ExprKind::Constant {
value: constant_piece.to_owned().into(),
kind: None,
}));
constant_piece.clear();
if in_nested {
return Err(UnclosedLbrace);
}
spec = Some(if nested {
Box::new(
self.expr(ExprKind::FormattedValue {
value: Box::new(
parse_fstring_expr(&spec_expression)
.map_err(|e| InvalidExpression(Box::new(e.error)))?,
),
conversion: None,
format_spec: None,
}),
)
} else {
Box::new(self.expr(ExprKind::Constant {
value: spec_expression.to_owned().into(),
kind: None,
}))
})
spec = Some(Box::new(self.expr(ExprKind::JoinedStr {
values: spec_constructor,
})))
}
'(' | '{' | '[' => {
expression.push(ch);
Expand Down Expand Up @@ -216,6 +235,10 @@ impl<'a> FStringParser<'a> {
}

fn parse(mut self) -> Result<Expr, FStringErrorType> {
if self.recurse_lvl >= 2 {
return Err(ExpressionNestedTooDeeply);
}

let mut content = String::new();
let mut values = vec![];

Expand Down Expand Up @@ -269,7 +292,7 @@ fn parse_fstring_expr(source: &str) -> Result<Expr, ParseError> {
/// Parse an fstring from a string, located at a certain position in the sourcecode.
/// In case of errors, we will get the location and the error returned.
pub fn parse_located_fstring(source: &str, location: Location) -> Result<Expr, FStringError> {
FStringParser::new(source, location)
FStringParser::new(source, location, 0)
.parse()
.map_err(|error| FStringError { error, location })
}
Expand All @@ -279,7 +302,7 @@ mod tests {
use super::*;

fn parse_fstring(source: &str) -> Result<Expr, FStringErrorType> {
FStringParser::new(source, Location::default()).parse()
FStringParser::new(source, Location::default(), 0).parse()
}

#[test]
Expand Down Expand Up @@ -347,7 +370,7 @@ mod tests {
assert_eq!(parse_fstring("{5!}"), Err(InvalidConversionFlag));
assert_eq!(parse_fstring("{5!x}"), Err(InvalidConversionFlag));

assert_eq!(parse_fstring("{a:{a:{b}}"), Err(ExpressionNestedTooDeeply));
assert_eq!(parse_fstring("{a:{a:{b}}}"), Err(ExpressionNestedTooDeeply));

assert_eq!(parse_fstring("{a:b}}"), Err(UnopenedRbrace));
assert_eq!(parse_fstring("}"), Err(UnopenedRbrace));
Expand Down
22 changes: 17 additions & 5 deletions ...rc/snapshots/rustpython_parser__fstring__tests__fstring_parse_selfdocumenting_format.snap
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
---
source: parser/src/fstring.rs
expression: parse_ast

---
Located {
location: Location {
Expand Down Expand Up @@ -62,11 +63,22 @@ Located {
column: 0,
},
custom: (),
node: Constant {
value: Str(
">10",
),
kind: None,
node: JoinedStr {
values: [
Located {
location: Location {
row: 0,
column: 0,
},
custom: (),
node: Constant {
value: Str(
">10",
),
kind: None,
},
},
],
},
},
),
Expand Down
83 changes: 71 additions & 12 deletions parser/src/snapshots/rustpython_parser__fstring__tests__parse_fstring_nested_spec.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -37,20 +37,79 @@ Located {
column: 0,
},
custom: (),
node: FormattedValue {
value: Located {
location: Location {
row: 1,
column: 2,
node: JoinedStr {
values: [
Located {
location: Location {
row: 0,
column: 0,
},
custom: (),
node: Constant {
value: Str(
"",
),
kind: None,
},
},
custom: (),
node: Name {
id: "spec",
ctx: Load,
Located {
location: Location {
row: 0,
column: 0,
},
custom: (),
node: FormattedValue {
value: Located {
location: Location {
row: 0,
column: 0,
},
custom: (),
node: JoinedStr {
values: [
Located {
location: Location {
row: 0,
column: 0,
},
custom: (),
node: FormattedValue {
value: Located {
location: Location {
row: 1,
column: 2,
},
custom: (),
node: Name {
id: "spec",
ctx: Load,
},
},
conversion: None,
format_spec: None,
},
},
],
},
},
conversion: None,
format_spec: None,
},
},
},
conversion: None,
format_spec: None,
Located {
location: Location {
row: 0,
column: 0,
},
custom: (),
node: Constant {
value: Str(
"",
),
kind: None,
},
},
],
},
},
),
Expand Down
21 changes: 16 additions & 5 deletions parser/src/snapshots/rustpython_parser__fstring__tests__parse_fstring_not_nested_spec.snap
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Original file line number Diff line number Diff line change
Expand Up @@ -37,11 +37,22 @@ Located {
column: 0,
},
custom: (),
node: Constant {
value: Str(
"spec",
),
kind: None,
node: JoinedStr {
values: [
Located {
location: Location {
row: 0,
column: 0,
},
custom: (),
node: Constant {
value: Str(
"spec",
),
kind: None,
},
},
],
},
},
),
Expand Down