Add support for indexing and attribute access inside format strings #2053
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youknowone
requested changes
Aug 1, 2020
vm/src/format.rs
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| fn parse_part( | ||
| chars: &mut impl PeekingNext<Item = char>, | ||
| ) -> Result<FieldNamePart, FormatParseError> { | ||
| let ch = chars.next().unwrap(); |
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Adding comment about safety guarantee from outside will be great
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I managed to avoid the need for this unwrap here by changing the return type to Result<Option<FieldNamePart>, FormatParseError>, which also made the use of this function more idiomatic.
vm/src/format.rs
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| if ch == '.' { | ||
| let mut attribute = String::new(); | ||
| for ch in chars.peeking_take_while(|ch| *ch != '.' && *ch != '[') { | ||
| attribute.push(ch); | ||
| } | ||
| if attribute.is_empty() { | ||
| Err(FormatParseError::EmptyAttribute) | ||
| } else { | ||
| Ok(FieldNamePart::Attribute(attribute)) | ||
| } | ||
| } else if ch == '[' { | ||
| let mut index = String::new(); | ||
| for ch in chars { | ||
| if ch == ']' { | ||
| return if index.is_empty() { | ||
| Err(FormatParseError::EmptyAttribute) | ||
| } else if let Ok(index) = index.parse::<usize>() { | ||
| Ok(FieldNamePart::Index(index)) | ||
| } else { | ||
| Ok(FieldNamePart::StringIndex(index)) | ||
| }; | ||
| } | ||
| index.push(ch); | ||
| } | ||
| Err(FormatParseError::MissingRightBracket) | ||
| } else { | ||
| Err(FormatParseError::InvalidCharacterAfterRightBracket) | ||
| } |
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Using match would be better to avoid chaining ch comparision.
match ch {
...
}Let me know if this is a straight-forward port of CPython if chaining implementation. In that case, we'd better to keep CPython related form.
vm/src/format.rs
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| pub(crate) field_type: FieldType, | ||
| pub(crate) parts: Vec<FieldNamePart>, |
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Suggested change
| pub(crate) field_type: FieldType, | |
| pub(crate) parts: Vec<FieldNamePart>, | |
| pub field_type: FieldType, | |
| pub parts: Vec<FieldNamePart>, |
The fields are always pub(crate) due to the struct visibility
vm/src/format.rs
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| #[derive(Debug, PartialEq)] | ||
| pub(crate) struct FormatString { | ||
| format_parts: Vec<FormatPart>, | ||
| pub(crate) format_parts: Vec<FormatPart>, |
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Suggested change
| pub(crate) format_parts: Vec<FormatPart>, | |
| pub format_parts: Vec<FormatPart>, |
youknowone
reviewed
Aug 1, 2020
| argument = vm.get_attribute(argument, attribute.as_str())?; | ||
| } | ||
| FieldNamePart::Index(index) => { | ||
| // TODO Implement DictKey for usize so we can pass index directly |
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It could be done without DictKey once #2035 is merged.
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| impl FromIterator<PyObjectRef> for PyList { | ||
| fn from_iter<T: IntoIterator<Item = PyObjectRef>>(iter: T) -> Self { | ||
| Vec::from_iter(iter).into() | ||
| } | ||
| } |
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youknowone
approved these changes
Aug 2, 2020
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"{a.attr}".format(...)and"{l[0]}".format(...)string.FormatterFor #1983