Start work on our own options parser

All the tests pass, but only half the functionality is there right now.

src/options/mod.rs

@@ -20,6 +20,8 @@ pub use self::misfire::Misfire;
 mod view;
 pub use self::view::{View, Mode};
 
+mod parser;
+
 
 /// These **options** represent a parsed, error-checked versions of the
 /// user’s command-line options.

src/options/parser.rs

+#![allow(unused_variables, dead_code)]
+
+use std::ffi::{OsStr, OsString};
+
+
+pub type ShortArg = u8;
+pub type LongArg = &'static str;
+
+
+#[derive(PartialEq, Debug)]
+pub enum Flag {
+    Short(ShortArg),
+    Long(LongArg),
+}
+
+#[derive(PartialEq, Debug)]
+pub enum Strictness {
+    ComplainAboutRedundantArguments,
+    UseLastArguments,
+}
+
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub enum TakesValue {
+    Necessary,
+    Forbidden,
+}
+
+#[derive(PartialEq, Debug)]
+pub struct Arg {
+    short: Option<ShortArg>,
+    long: LongArg,
+    takes_value: TakesValue,
+}
+
+#[derive(PartialEq, Debug)]
+pub struct Args(&'static [Arg]);
+
+impl Args {
+    fn lookup_short(&self, short: ShortArg) -> Option<&Arg> {
+        self.0.into_iter().find(|arg| arg.short == Some(short))
+    }
+
+    fn lookup_long(&self, long: &OsStr) -> Option<&Arg> {
+        self.0.into_iter().find(|arg| arg.long == long)
+    }
+}
+
+
+#[derive(PartialEq, Debug)]
+pub struct Matches<'a> {
+    /// Long and short arguments need to be kept in the same vector, because
+    /// we usually want the one nearest the end to count.
+    flags: Vec<(Flag, Option<&'a OsStr>)>,
+    frees: Vec<&'a OsStr>,
+}
+
+#[derive(PartialEq, Debug)]
+pub enum ParseError<'a> {
+    NeedsValue { flag: Flag },
+    ForbiddenValue { flag: Flag },
+    UnknownShortArgument { attempt: ShortArg },
+    UnknownArgument { attempt: &'a OsStr },
+}
+
+
+fn parse<'a>(args: Args, inputs: &'a [OsString]) -> Result<Matches<'a>, ParseError<'a>> {
+    use std::os::unix::ffi::OsStrExt;
+    use self::TakesValue::*;
+
+    let mut parsing = true;
+
+    let mut results = Matches {
+        flags: Vec::new(),
+        frees: Vec::new(),
+    };
+
+    let mut iter = inputs.iter();
+
+    while let Some(arg) = iter.next() {
+        let bytes = arg.as_bytes();
+
+        if !parsing {
+            results.frees.push(arg)
+        }
+        else if arg == "--" {
+            parsing = false;
+        }
+        else if bytes.starts_with(b"--") {
+            let long_arg = OsStr::from_bytes(&bytes[2..]);
+
+            if let Some((before, after)) = split_on_equals(long_arg) {
+                if let Some(&Arg { short: _, long: long_arg_name, takes_value }) = args.lookup_long(before) {
+                    let flag = Flag::Long(long_arg_name);
+                    match takes_value {
+                        Necessary  => results.flags.push((flag, Some(after))),
+                        Forbidden  => return Err(ParseError::ForbiddenValue { flag })
+                    }
+                }
+                else {
+                    return Err(ParseError::UnknownArgument { attempt: before })
+                }
+            }
+            else {
+                if let Some(&Arg { short: _, long: long_arg_name, takes_value }) = args.lookup_long(long_arg) {
+                    let flag = Flag::Long(long_arg_name);
+                    match takes_value {
+                        Forbidden  => results.flags.push((flag, None)),
+                        Necessary  => {
+                            if let Some(next_arg) = iter.next() {
+                                results.flags.push((flag, Some(next_arg)));
+                            }
+                            else {
+                                return Err(ParseError::NeedsValue { flag })
+                            }
+                        }
+                    }
+                }
+                else {
+                    return Err(ParseError::UnknownArgument { attempt: long_arg })
+                }
+            }
+        }
+        else if bytes.starts_with(b"-") && arg != "-" {
+            let short_arg = OsStr::from_bytes(&bytes[1..]);
+            if let Some((before, after)) = split_on_equals(short_arg) {
+                // TODO: remember to deal with the other bytes!
+                if let Some(&Arg { short, long, takes_value }) = args.lookup_short(*before.as_bytes().last().unwrap()) {
+                    let flag = Flag::Short(short.unwrap());
+                    match takes_value {
+                        Necessary  => results.flags.push((flag, Some(after))),
+                        Forbidden  => return Err(ParseError::ForbiddenValue { flag })
+                    }
+                }
+                else {
+                    return Err(ParseError::UnknownArgument { attempt: before })
+                }
+            }
+            else {
+                for byte in &bytes[1..] {
+                    // TODO: gotta check that these don't take arguments
+                    // like -c4
+                    if let Some(&Arg { short, long, takes_value }) = args.lookup_short(*byte) {
+                        let flag = Flag::Short(*byte);
+                        match takes_value {
+                            Forbidden  => results.flags.push((flag, None)),
+                            Necessary  => {
+                                if let Some(next_arg) = iter.next() {
+                                    results.flags.push((flag, Some(next_arg)));
+                                }
+                                else {
+                                    return Err(ParseError::NeedsValue { flag })
+                                }
+                            }
+                        }
+                    }
+                    else {
+                        return Err(ParseError::UnknownShortArgument { attempt: *byte });
+                    }
+                }
+            }
+        }
+        else {
+            results.frees.push(arg)
+        }
+    }
+
+    Ok(results)
+}
+
+
+fn split_on_equals<'a>(input: &OsStr) -> Option<(&OsStr, &OsStr)> {
+    use std::os::unix::ffi::OsStrExt;
+
+    input.as_bytes()
+         .iter()
+         .position(|elem| *elem == b'=')
+         .map(|index| input.as_bytes().split_at(index))
+         .map(|(b,a)| (OsStr::from_bytes(b), OsStr::from_bytes(&a[1..])))
+}
+
+
+
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use std::ffi::OsString;
+
+    static TEST_ARGS: &'static [Arg] = &[
+        Arg { short: Some(b'l'), long: "long",  takes_value: TakesValue::Forbidden },
+        Arg { short: Some(b'c'), long: "count", takes_value: TakesValue::Necessary }
+    ];
+
+    fn os(input: &'static str) -> OsString {
+        let mut os = OsString::new();
+        os.push(input);
+        os
+    }
+
+    #[test]
+    fn empty() {
+        let bits = [ ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![] }))
+    }
+
+    #[test]
+    fn filename() {
+        let bits = [ os("exa") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![ os("exa").as_os_str() ], flags: vec![] }))
+    }
+
+    #[test]
+    fn the_dashes_do_nothing() {
+        let bits = [ os("--") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![] }))
+    }
+
+    #[test]
+    fn but_just_one_does() {
+        let bits = [ os("-") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![ os("-").as_os_str() ], flags: vec![] }))
+    }
+
+
+
+    // ----- long args --------
+
+    #[test]
+    fn as_filename() {
+        let bits = [ os("--"), os("--long") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![os("--long").as_os_str() ], flags: vec![] }))
+    }
+
+
+    #[test]
+    fn long() {
+        let bits = [ os("--long") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![ (Flag::Long("long"), None) ] }))
+    }
+
+    #[test]
+    fn long_equals() {
+        let bits = [ os("--long=equals") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Err(ParseError::ForbiddenValue { flag: Flag::Long("long") }))
+    }
+
+    #[test]
+    fn no_arg_separate() {
+        let bits = [ os("--long"), os("4") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![ os("4").as_os_str() ], flags: vec![ (Flag::Long("long"), None) ] }))
+    }
+
+
+    #[test]
+    fn no_arg_given() {
+        let bits = [ os("--count") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Err(ParseError::NeedsValue { flag: Flag::Long("count") }))
+    }
+
+    #[test]
+    fn arg_equals() {
+        let bits = [ os("--count=4") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![ (Flag::Long("count"), Some(os("4").as_os_str())) ] }))
+    }
+
+    #[test]
+    fn arg_separate() {
+        let bits = [ os("--count"), os("4") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![ (Flag::Long("count"), Some(os("4").as_os_str())) ] }))
+    }
+
+
+
+
+
+
+    // ----- short args --------
+
+    #[test]
+    fn short_as_filename() {
+        let bits = [ os("--"), os("-l") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![os("-l").as_os_str() ], flags: vec![] }))
+    }
+
+
+    #[test]
+    fn short_long() {
+        let bits = [ os("-l") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![ (Flag::Short(b'l'), None) ] }))
+    }
+
+    #[test]
+    fn short_long_equals() {
+        let bits = [ os("-l=equals") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Err(ParseError::ForbiddenValue { flag: Flag::Short(b'l') }))
+    }
+
+    #[test]
+    fn short_no_arg_separate() {
+        let bits = [ os("-l"), os("4") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![ os("4").as_os_str() ], flags: vec![ (Flag::Short(b'l'), None) ] }))
+    }
+
+
+    #[test]
+    fn short_no_arg_given() {
+        let bits = [ os("-c") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Err(ParseError::NeedsValue { flag: Flag::Short(b'c') }))
+    }
+
+    #[test]
+    fn short_arg_equals() {
+        let bits = [ os("-c=4") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![ (Flag::Short(b'c'), Some(os("4").as_os_str())) ] }))
+    }
+
+    #[test]
+    fn short_arg_separate() {
+        let bits = [ os("-c"), os("4") ];
+        let results = parse(Args(TEST_ARGS), &bits);
+        assert_eq!(results, Ok(Matches { frees: vec![], flags: vec![ (Flag::Short(b'c'), Some(os("4").as_os_str())) ] }))
+    }
+
+}