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Merge #156: Field splitting (and empty field removal)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,221 @@ | ||
| // This file is part of yash, an extended POSIX shell. | ||
| // Copyright (C) 2022 WATANABE Yuki | ||
| // | ||
| // This program is free software: you can redistribute it and/or modify | ||
| // it under the terms of the GNU General Public License as published by | ||
| // the Free Software Foundation, either version 3 of the License, or | ||
| // (at your option) any later version. | ||
| // | ||
| // This program is distributed in the hope that it will be useful, | ||
| // but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | ||
| // GNU General Public License for more details. | ||
| // | ||
| // You should have received a copy of the GNU General Public License | ||
| // along with this program. If not, see <https://www.gnu.org/licenses/>. | ||
|
|
||
| //! Field splitting | ||
| //! | ||
| //! The field splitting divides a field into smaller parts delimited by a field | ||
| //! separator character. Fields are delimited by a field separator character, | ||
| //! usually obtained from the `$IFS` variable. Every occurrence of a | ||
| //! non-whitespace separator delimits a new field (which may be an empty field). | ||
| //! One or more adjacent whitespace separators in the middle of a field further | ||
| //! split the field. Any separator does not remain in the final results. | ||
| //! | ||
| //! Only [unquoted characters](AttrChar) having a `SoftExpansion` | ||
| //! [origin](Origin) are considered for delimiting. Other characters are not | ||
| //! subject to field splitting. | ||
| //! | ||
| //! # Example | ||
| //! | ||
| //! ``` | ||
| //! use yash_syntax::source::Location; | ||
| //! use yash_semantics::expansion::attr::{AttrChar, AttrField, Origin}; | ||
| //! use yash_semantics::expansion::split::{Ifs, split}; | ||
| //! | ||
| //! // We use this utility to prepare fields used in the examples below: | ||
| //! fn field(s: &str) -> AttrField { | ||
| //! let chars = s.chars() | ||
| //! .map(|c| AttrChar { | ||
| //! value: c, | ||
| //! origin: Origin::SoftExpansion, | ||
| //! is_quoted: false, | ||
| //! is_quoting: false, | ||
| //! }) | ||
| //! .collect(); | ||
| //! let origin = Location::dummy(""); | ||
| //! AttrField { chars, origin } | ||
| //! } | ||
| //! | ||
| //! let ifs = Ifs::new(" -"); | ||
| //! | ||
| //! // When there are no separators in the input, the result is the input itself: | ||
| //! let fields: Vec<AttrField> = split(field("abc"), &ifs); | ||
| //! assert_eq!(fields, [field("abc")]); | ||
| //! | ||
| //! // Whitespace separators are removed: | ||
| //! let fields: Vec<AttrField> = split(field(" abc "), &ifs); | ||
| //! assert_eq!(fields, [field("abc")]); | ||
| //! | ||
| //! // An empty input yields no fields rather than an empty field: | ||
| //! let fields: Vec<AttrField> = split(field(""), &ifs); | ||
| //! assert_eq!(fields, []); | ||
| //! | ||
| //! // Whitespace separators split fields: | ||
| //! let fields: Vec<AttrField> = split(field("foo bar baz"), &ifs); | ||
| //! assert_eq!(fields, [field("foo"), field("bar"), field("baz")]); | ||
| //! | ||
| //! // Non-whitespace separators each split fields, which may produce empty fields: | ||
| //! let fields: Vec<AttrField> = split(field("foo-bar--baz"), &ifs); | ||
| //! assert_eq!(fields, [field("foo"), field("bar"), field(""), field("baz")]); | ||
| //! | ||
| //! // Whitespace separators around non-whitespace separators are ignored: | ||
| //! let fields: Vec<AttrField> = split(field("foo - bar - - baz"), &ifs); | ||
| //! assert_eq!(fields, [field("foo"), field("bar"), field(""), field("baz")]); | ||
| //! | ||
| //! // Trailing non-whitespace separators may seem special: | ||
| //! let fields: Vec<AttrField> = split(field("foo-bar"), &ifs); | ||
| //! assert_eq!(fields, [field("foo"), field("bar")]); | ||
| //! let fields: Vec<AttrField> = split(field("foo-bar-"), &ifs); | ||
| //! assert_eq!(fields, [field("foo"), field("bar")]); | ||
| //! let fields: Vec<AttrField> = split(field("foo-bar--"), &ifs); | ||
| //! assert_eq!(fields, [field("foo"), field("bar"), field("")]); | ||
| //! ``` | ||
| //! | ||
| //! # The empty-last-field option | ||
| //! | ||
| //! TODO: Not yet supported | ||
|
|
||
| mod ifs; | ||
| mod ranges; | ||
|
|
||
| pub use self::ifs::{Class, Ifs}; | ||
| pub use self::ranges::Ranges; | ||
|
|
||
| use super::attr::AttrField; | ||
| #[cfg(doc)] | ||
| use super::attr::{AttrChar, Origin}; | ||
|
|
||
| /// Performs field splitting and appends the result to a collection. | ||
| /// | ||
| /// This function applies field splitting to the given field using the given IFS | ||
| /// and extends the given collection with the results. The resultant fields | ||
| /// share the same origin as the input field. | ||
| /// | ||
| /// See also [`split`], which returns the results in a new collection rather | ||
| /// than extending an existing one. | ||
| pub fn split_into<R>(field: AttrField, ifs: &Ifs, results: &mut R) | ||
| where | ||
| R: Extend<AttrField>, | ||
| { | ||
| /* | ||
| results.extend( | ||
| ifs.ranges(field.chars.iter().copied()) | ||
| .map(|range| AttrField { | ||
| chars: field.chars[range].to_vec(), | ||
| origin: field.origin.clone(), | ||
| }), | ||
| ); | ||
| */ | ||
|
|
||
| // Optimize by reusing the original field for the last one. | ||
| let mut ranges = ifs.ranges(field.chars.iter().copied()).peekable(); | ||
| while let Some(range) = ranges.next() { | ||
| // TODO Use Extend::extend_one when stabilized (rust#72631) | ||
| if ranges.peek().is_some() { | ||
| results.extend(std::iter::once(AttrField { | ||
| chars: field.chars[range].to_vec(), | ||
| origin: field.origin.clone(), | ||
| })); | ||
| } else { | ||
| let mut field = field; | ||
| field.chars.truncate(range.end); | ||
| field.chars.drain(..range.start); | ||
| results.extend(std::iter::once(field)); | ||
| break; | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// Performs field splitting and returns the result in a new collection. | ||
| /// | ||
| /// This function works similarly to [`split_into`], but returns the results in | ||
| /// a new collection. | ||
| pub fn split<R>(field: AttrField, ifs: &Ifs) -> R | ||
| where | ||
| R: Default + Extend<AttrField>, | ||
| { | ||
| let mut results = R::default(); | ||
| split_into(field, ifs, &mut results); | ||
| results | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::super::attr::{AttrChar, Origin}; | ||
| use super::*; | ||
| use yash_syntax::source::Location; | ||
|
|
||
| fn dummy_attr_field(s: &str) -> AttrField { | ||
| let chars = s | ||
| .chars() | ||
| .map(|c| AttrChar { | ||
| value: c, | ||
| origin: Origin::SoftExpansion, | ||
| is_quoted: false, | ||
| is_quoting: false, | ||
| }) | ||
| .collect(); | ||
| let origin = Location::dummy(""); | ||
| AttrField { chars, origin } | ||
| } | ||
|
|
||
| #[test] | ||
| fn split_empty_field() { | ||
| let field = dummy_attr_field(""); | ||
| let ifs = Ifs::default(); | ||
| let fields: Vec<AttrField> = split(field, &ifs); | ||
| assert_eq!(fields, []); | ||
| } | ||
|
|
||
| #[test] | ||
| fn split_no_change() { | ||
| let field = dummy_attr_field("abc"); | ||
| let ifs = Ifs::default(); | ||
| let fields: Vec<AttrField> = split(field, &ifs); | ||
| assert_eq!(fields, [dummy_attr_field("abc")]); | ||
| } | ||
|
|
||
| #[test] | ||
| fn split_into_one_field() { | ||
| let field = dummy_attr_field(" foo "); | ||
| let ifs = Ifs::default(); | ||
| let fields: Vec<AttrField> = split(field, &ifs); | ||
| assert_eq!(fields, [dummy_attr_field("foo")]); | ||
| } | ||
|
|
||
| #[test] | ||
| fn split_into_two_fields() { | ||
| let field = dummy_attr_field("foo bar"); | ||
| let ifs = Ifs::default(); | ||
| let fields: Vec<AttrField> = split(field, &ifs); | ||
| assert_eq!(fields, [dummy_attr_field("foo"), dummy_attr_field("bar")]); | ||
| } | ||
|
|
||
| #[test] | ||
| fn split_into_many_fields() { | ||
| let field = dummy_attr_field(" one two three four "); | ||
| let ifs = Ifs::default(); | ||
| let fields: Vec<AttrField> = split(field, &ifs); | ||
| assert_eq!( | ||
| fields, | ||
| [ | ||
| dummy_attr_field("one"), | ||
| dummy_attr_field("two"), | ||
| dummy_attr_field("three"), | ||
| dummy_attr_field("four") | ||
| ] | ||
| ); | ||
| } | ||
| } |
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