parse git-ignore files

git-attributes/Cargo.toml

@@ -13,3 +13,8 @@ doctest = false
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+bstr = { version = "0.2.13", default-features = false, features = ["std"]}
+bitflags = "1.3.2"
+
+[dev-dependencies]
+git-testtools = { path = "../tests/tools"}

git-attributes/src/ignore.rs

@@ -0,0 +1,15 @@
+pub mod pattern {
+    use bitflags::bitflags;
+
+    bitflags! {
+        pub struct Mode: u32 {
+            /// The pattern does not contain a sub-directory and - it doesn't contain slashes after removing the trailing one.
+            const NO_SUB_DIR = 1 << 0;
+            /// A pattern that is '*literal', meaning that it ends with what's given here
+            const ENDS_WITH = 1 << 1;
+            /// The pattern must match a directory, and not a file.
+            const MUST_BE_DIR = 1 << 2;
+            const NEGATIVE = 1 << 3;
+        }
+    }
+}

git-attributes/src/lib.rs

@@ -1 +1,5 @@
 #![forbid(unsafe_code, rust_2018_idioms)]
+
+pub mod ignore;
+
+pub mod parse;

git-attributes/src/parse/ignore.rs

@@ -0,0 +1,90 @@
+use crate::ignore;
+use bstr::{BString, ByteSlice};
+
+pub struct Iter<'a> {
+    lines: bstr::Lines<'a>,
+    line_no: usize,
+}
+
+impl<'a> Iter<'a> {
+    pub fn new(buf: &'a [u8]) -> Self {
+        Iter {
+            lines: buf.lines(),
+            line_no: 0,
+        }
+    }
+}
+
+impl<'a> Iterator for Iter<'a> {
+    type Item = (BString, ignore::pattern::Mode, usize);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut res = None;
+        for mut line in self.lines.by_ref() {
+            self.line_no += 1;
+            let mut mode = ignore::pattern::Mode::empty();
+            if line.is_empty() {
+                continue;
+            };
+            if line.first() == Some(&b'#') {
+                continue;
+            } else if line.first() == Some(&b'!') {
+                mode |= ignore::pattern::Mode::NEGATIVE;
+                line = &line[1..];
+            } else if line.first() == Some(&b'\\') {
+                let second = line.get(1);
+                if second == Some(&b'!') || second == Some(&b'#') {
+                    line = &line[1..];
+                }
+            }
+            let mut line = truncate_non_escaped_trailing_spaces(line);
+            if line.last() == Some(&b'/') {
+                mode |= ignore::pattern::Mode::MUST_BE_DIR;
+                line.pop();
+            }
+            if !line.contains(&b'/') {
+                mode |= ignore::pattern::Mode::NO_SUB_DIR;
+            }
+            if line.first() == Some(&b'*') && line[1..].find_byteset(br"*?[\").is_none() {
+                mode |= ignore::pattern::Mode::ENDS_WITH;
+            }
+            res = Some((line, mode, self.line_no));
+            break;
+        }
+        res
+    }
+}
+
+/// We always copy just because that's ultimately needed anyway, not because we always have to.
+fn truncate_non_escaped_trailing_spaces(buf: &[u8]) -> BString {
+    match buf.rfind_not_byteset(br"\ ") {
+        Some(pos) if pos + 1 == buf.len() => buf.into(), // does not end in (escaped) whitespace
+        None => buf.into(),
+        Some(start_of_non_space) => {
+            // This seems a bit strange but attempts to recreate the git implementation while
+            // actually removing the escape characters before spaces. We leave other backslashes
+            // for escapes to be handled by `glob/globset`.
+            let mut res: BString = buf[..start_of_non_space + 1].into();
+
+            let mut trailing_bytes = buf[start_of_non_space + 1..].iter();
+            let mut bare_spaces = 0;
+            while let Some(b) = trailing_bytes.next() {
+                match b {
+                    b' ' => {
+                        bare_spaces += 1;
+                    }
+                    b'\\' => {
+                        res.extend(std::iter::repeat(b' ').take(bare_spaces));
+                        bare_spaces = 0;
+                        // Skip what follows, like git does, but keep spaces if possible.
+                        if trailing_bytes.next() == Some(&b' ') {
+                            res.push(b' ');
+                        }
+                    }
+                    _ => unreachable!("BUG: this must be either backslash or space"),
+                }
+            }
+            res
+        }
+    }
+}

git-attributes/src/parse/mod.rs

@@ -0,0 +1,5 @@
+pub mod ignore;
+
+pub fn ignore(buf: &[u8]) -> ignore::Iter<'_> {
+    ignore::Iter::new(buf)
+}

git-attributes/tests/attributes.rs

@@ -0,0 +1,175 @@
+mod parse {
+    mod ignore {
+        use git_attributes::ignore::pattern::Mode;
+        use git_testtools::fixture_path;
+
+        #[test]
+        fn line_numbers_are_counted_correctly() {
+            let ignore = std::fs::read(fixture_path("ignore/various.txt")).unwrap();
+            let actual: Vec<_> = git_attributes::parse::ignore(&ignore).collect();
+            assert_eq!(
+                actual,
+                vec![
+                    ("*.[oa]".into(), Mode::NO_SUB_DIR, 2),
+                    ("*.html".into(), Mode::NO_SUB_DIR | Mode::ENDS_WITH, 5),
+                    ("foo.html".into(), Mode::NO_SUB_DIR | Mode::NEGATIVE, 8),
+                    ("/*".into(), Mode::empty(), 11),
+                    ("/foo".into(), Mode::NEGATIVE, 12),
+                    ("/foo/*".into(), Mode::empty(), 13),
+                    ("/foo/bar".into(), Mode::NEGATIVE, 14)
+                ]
+            );
+        }
+
+        #[test]
+        fn line_endings_can_be_windows_or_unix() {
+            assert_eq!(
+                git_attributes::parse::ignore(b"unix\nwindows\r\nlast").collect::<Vec<_>>(),
+                vec![
+                    (r"unix".into(), Mode::NO_SUB_DIR, 1),
+                    (r"windows".into(), Mode::NO_SUB_DIR, 2),
+                    (r"last".into(), Mode::NO_SUB_DIR, 3)
+                ]
+            );
+        }
+
+        #[test]
+        fn mark_ends_with_pattern_specifically() {
+            assert_eq!(
+                git_attributes::parse::ignore(br"*literal").next(),
+                Some((r"*literal".into(), Mode::NO_SUB_DIR | Mode::ENDS_WITH, 1))
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"**literal").next(),
+                Some((r"**literal".into(), Mode::NO_SUB_DIR, 1)),
+                "double-asterisk won't allow for fast comparisons"
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"*litera[l]").next(),
+                Some((r"*litera[l]".into(), Mode::NO_SUB_DIR, 1))
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"*litera?").next(),
+                Some((r"*litera?".into(), Mode::NO_SUB_DIR, 1))
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"*litera\?").next(),
+                Some((r"*litera\?".into(), Mode::NO_SUB_DIR, 1)),
+                "for now we don't handle escapes properly like git seems to do"
+            );
+        }
+
+        #[test]
+        fn comments_are_ignored() {
+            assert!(git_attributes::parse::ignore(b"# hello world").next().is_none());
+        }
+
+        #[test]
+        fn backslashes_before_hashes_are_no_comments() {
+            assert_eq!(
+                git_attributes::parse::ignore(br"\#hello").next(),
+                Some((r"#hello".into(), Mode::NO_SUB_DIR, 1))
+            );
+        }
+
+        #[test]
+        fn backslashes_are_part_of_the_pattern_if_not_in_specific_positions() {
+            assert_eq!(
+                git_attributes::parse::ignore(br"\hello\world").next(),
+                Some((r"\hello\world".into(), Mode::NO_SUB_DIR, 1))
+            );
+        }
+
+        #[test]
+        fn leading_exclamation_mark_negates_pattern() {
+            assert_eq!(
+                git_attributes::parse::ignore(b"!hello").next(),
+                Some(("hello".into(), Mode::NEGATIVE | Mode::NO_SUB_DIR, 1))
+            );
+        }
+
+        #[test]
+        fn leading_exclamation_marks_can_be_escaped_with_backslash() {
+            assert_eq!(
+                git_attributes::parse::ignore(br"\!hello").next(),
+                Some(("!hello".into(), Mode::NO_SUB_DIR, 1))
+            );
+        }
+
+        #[test]
+        fn absence_of_sub_directories_are_marked() {
+            assert_eq!(
+                git_attributes::parse::ignore(br"a/b").next(),
+                Some(("a/b".into(), Mode::empty(), 1))
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"ab").next(),
+                Some(("ab".into(), Mode::NO_SUB_DIR, 1))
+            );
+        }
+
+        #[test]
+        fn trailing_slashes_are_marked_and_removed() {
+            assert_eq!(
+                git_attributes::parse::ignore(b"dir/").next(),
+                Some(("dir".into(), Mode::MUST_BE_DIR | Mode::NO_SUB_DIR, 1))
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(b"dir///").next(),
+                Some(("dir//".into(), Mode::MUST_BE_DIR, 1)),
+                "but only the last slash is removed"
+            );
+        }
+
+        #[test]
+        fn trailing_spaces_are_ignored() {
+            assert_eq!(
+                git_attributes::parse::ignore(br"a   ").next(),
+                Some(("a".into(), Mode::NO_SUB_DIR, 1))
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(b"a\t\t  ").next(),
+                Some(("a\t\t".into(), Mode::NO_SUB_DIR, 1)),
+                "trailing tabs are not ignored"
+            );
+        }
+        #[test]
+        fn trailing_spaces_can_be_escaped_to_be_literal() {
+            assert_eq!(
+                git_attributes::parse::ignore(br"a  \ ").next(),
+                Some(("a   ".into(), Mode::NO_SUB_DIR, 1)),
+                "a single escape in front of the last desired space is enough"
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"a  b  c ").next(),
+                Some(("a  b  c".into(), Mode::NO_SUB_DIR, 1)),
+                "spaces in the middle are fine"
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"a\ \ \ ").next(),
+                Some(("a   ".into(), Mode::NO_SUB_DIR, 1)),
+                "one can also escape every single one"
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"a \  ").next(),
+                Some(("a  ".into(), Mode::NO_SUB_DIR, 1)),
+                "or just the one in the middle, losing the last actual space"
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"a   \").next(),
+                Some(("a   ".into(), Mode::NO_SUB_DIR, 1)),
+                "escaping nothing also works as a whitespace protection"
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"a   \\\ ").next(),
+                Some((r"a    ".into(), Mode::NO_SUB_DIR, 1)),
+                "strange things like these work too"
+            );
+            assert_eq!(
+                git_attributes::parse::ignore(br"a   \\ ").next(),
+                Some((r"a   ".into(), Mode::NO_SUB_DIR, 1)),
+                "strange things like these work as well"
+            );
+        }
+    }
+}

git-attributes/tests/fixtures/ignore/various.txt

@@ -0,0 +1,14 @@
+# ignore objects and archives, anywhere in the tree.
+*.[oa]
+
+# ignore generated html files,
+*.html
+
+# except foo.html which is maintained by hand
+!foo.html
+
+# exclude everything except directory foo/bar
+/*
+!/foo
+/foo/*
+!/foo/bar