Add %#z as "Permissive" timezone parsing

This allows you to parse a timezone that:

* Is either `Z` or an actual offset
* Contains no minutes, just the hour

Fixes #219

src/format/mod.rs

@@ -200,6 +200,15 @@ pub enum Fixed {
     /// Same to [`TimezoneOffsetColonZ`](#variant.TimezoneOffsetColonZ) but prints no colon.
     /// Parsing allows an optional colon.
     TimezoneOffsetZ,
+    /// Same as [`TimezoneOffsetColonZ`](#variant.TimezoneOffsetColonZ), but
+    /// allows missing minutes (per [ISO 8601][iso8601]).
+    ///
+    /// # Panics
+    ///
+    /// If you try to use this for printing.
+    ///
+    /// [iso8601]: https://en.wikipedia.org/wiki/ISO_8601#Time_offsets_from_UTC
+    TimezoneOffsetPermissive,
     /// RFC 2822 date and time syntax. Commonly used for email and MIME date and time.
     RFC2822,
     /// RFC 3339 & ISO 8601 date and time syntax.
@@ -491,6 +500,8 @@ pub fn format<'a, I>(w: &mut fmt::Formatter, date: Option<&NaiveDate>, time: Opt
                         off.map(|&(_, off)| write_local_minus_utc(w, off, false, false)),
                     TimezoneOffsetZ =>
                         off.map(|&(_, off)| write_local_minus_utc(w, off, true, false)),
+                    TimezoneOffsetPermissive =>
+                        panic!("Do not try to write %#z it is undefined"),
                     RFC2822 => // same to `%a, %e %b %Y %H:%M:%S %z`
                         if let (Some(d), Some(t), Some(&(_, off))) = (date, time, off) {
                             let sec = t.second() + t.nanosecond() / 1_000_000_000;
@@ -609,4 +620,3 @@ impl FromStr for Weekday {
         }
     }
 }
-

src/format/parse.rs

@@ -328,6 +328,11 @@ pub fn parse<'a, I>(parsed: &mut Parsed, mut s: &str, items: I) -> ParseResult<(
                                                                              scan::colon_or_space));
                         try!(parsed.set_offset(i64::from(offset)));
                     }
+                    TimezoneOffsetPermissive => {
+                        let offset = try_consume!(scan::timezone_offset_permissive(
+                            s.trim_left(), scan::colon_or_space));
+                        try!(parsed.set_offset(i64::from(offset)));
+                    }
 
                     RFC2822 => try_consume!(parse_rfc2822(parsed, s)),
                     RFC3339 => try_consume!(parse_rfc3339(parsed, s)),
@@ -570,6 +575,10 @@ fn test_parse() {
     check!("zulu",      [fix!(TimezoneOffsetZ), lit!("ulu")]; offset: 0);
     check!("+1234ulu",  [fix!(TimezoneOffsetZ), lit!("ulu")]; offset: 754 * 60);
     check!("+12:34ulu", [fix!(TimezoneOffsetZ), lit!("ulu")]; offset: 754 * 60);
+    check!("Z",         [fix!(TimezoneOffsetPermissive)]; offset: 0);
+    check!("z",         [fix!(TimezoneOffsetPermissive)]; offset: 0);
+    check!("+12:00",    [fix!(TimezoneOffsetPermissive)]; offset: 12 * 60 * 60);
+    check!("+12",       [fix!(TimezoneOffsetPermissive)]; offset: 12 * 60 * 60);
     check!("???",       [fix!(TimezoneName)]; BAD_FORMAT); // not allowed
 
     // some practical examples

src/format/scan.rs

@@ -171,8 +171,15 @@ pub fn colon_or_space(s: &str) -> ParseResult<&str> {
 ///
 /// The additional `colon` may be used to parse a mandatory or optional `:`
 /// between hours and minutes, and should return either a new suffix or `Err` when parsing fails.
-pub fn timezone_offset<F>(mut s: &str, mut colon: F) -> ParseResult<(&str, i32)>
+pub fn timezone_offset<F>(s: &str, consume_colon: F) -> ParseResult<(&str, i32)>
         where F: FnMut(&str) -> ParseResult<&str> {
+    timezone_offset_internal(s, consume_colon, false)
+}
+
+fn timezone_offset_internal<F>(mut s: &str, mut consume_colon: F, allow_missing_minutes: bool)
+-> ParseResult<(&str, i32)>
+    where F: FnMut(&str) -> ParseResult<&str>
+{
     fn digits(s: &str) -> ParseResult<(u8, u8)> {
         let b = s.as_bytes();
         if b.len() < 2 {
@@ -197,29 +204,54 @@ pub fn timezone_offset<F>(mut s: &str, mut colon: F) -> ParseResult<(&str, i32)>
     s = &s[2..];
 
     // colons (and possibly other separators)
-    s = try!(colon(s));
+    s = try!(consume_colon(s));
 
     // minutes (00--59)
-    let minutes = match try!(digits(s)) {
+    // if the next two items are digits then we have to add minutes
+    let minutes = if let Ok(ds) = digits(s) {
+        match ds {
             (m1 @ b'0'...b'5', m2 @ b'0'...b'9') => i32::from((m1 - b'0') * 10 + (m2 - b'0')),
             (b'6'...b'9', b'0'...b'9') => return Err(OUT_OF_RANGE),
             _ => return Err(INVALID),
+        }
+    } else if allow_missing_minutes {
+        0
+    } else {
+        return Err(TOO_SHORT);
+    };
+    s = match s.len() {
+        len if len >= 2 => &s[2..],
+        len if len == 0 => s,
+        _ => return Err(TOO_SHORT),
     };
-    s = &s[2..];
 
     let seconds = hours * 3600 + minutes * 60;
     Ok((s, if negative {-seconds} else {seconds}))
 }
 
 /// Same to `timezone_offset` but also allows for `z`/`Z` which is same to `+00:00`.
-pub fn timezone_offset_zulu<F>(s: &str, colon: F) -> ParseResult<(&str, i32)>
+pub fn timezone_offset_zulu<F>(s: &str, colon: F)
-        where F: FnMut(&str) -> ParseResult<&str> {
+-> ParseResult<(&str, i32)>
+    where F: FnMut(&str) -> ParseResult<&str>
+{
     match s.as_bytes().first() {
         Some(&b'z') | Some(&b'Z') => Ok((&s[1..], 0)),
         _ => timezone_offset(s, colon),
     }
 }
 
+/// Same to `timezone_offset` but also allows for `z`/`Z` which is same to
+/// `+00:00`, and allows missing minutes entirely.
+pub fn timezone_offset_permissive<F>(s: &str, colon: F)
+-> ParseResult<(&str, i32)>
+    where F: FnMut(&str) -> ParseResult<&str>
+{
+    match s.as_bytes().first() {
+        Some(&b'z') | Some(&b'Z') => Ok((&s[1..], 0)),
+        _ => timezone_offset_internal(s, colon, true),
+    }
+}
+
 /// Same to `timezone_offset` but also allows for RFC 2822 legacy timezones.
 /// May return `None` which indicates an insufficient offset data (i.e. `-0000`).
 pub fn timezone_offset_2822(s: &str) -> ParseResult<(&str, Option<i32>)> {

src/format/strftime.rs

@@ -68,6 +68,7 @@ The following specifiers are available both to formatting and parsing.
 | `%Z`  | `ACST`   | *Formatting only:* Local time zone name.                                   |
 | `%z`  | `+0930`  | Offset from the local time to UTC (with UTC being `+0000`).                |
 | `%:z` | `+09:30` | Same to `%z` but with a colon.                                             |
+| `%#z` | `+09`    | *Parsing only:* Same to `%z` but allows minutes to be missing or present.  |
 |       |          |                                                                            |
 |       |          | **DATE & TIME SPECIFIERS:**                                                |
 |`%c`|`Sun Jul  8 00:34:60 2001`|`ctime` date & time format. Same to `%a %b %e %T %Y` sans `\n`.|
@@ -167,6 +168,8 @@ impl<'a> StrftimeItems<'a> {
     }
 }
 
+const HAVE_ALTERNATES: &str = "z";
+
 impl<'a> Iterator for StrftimeItems<'a> {
     type Item = Item<'a>;
 
@@ -205,7 +208,11 @@ impl<'a> Iterator for StrftimeItems<'a> {
                     '_' => Some(Pad::Space),
                     _ => None,
                 };
-                let spec = if pad_override.is_some() { next!() } else { spec };
+                let is_alternate = spec == '#';
+                let spec = if pad_override.is_some() || is_alternate { next!() } else { spec };
+                if is_alternate && !HAVE_ALTERNATES.contains(spec) {
+                    return Some(Item::Error);
+                }
 
                 macro_rules! recons {
                     [$head:expr, $($tail:expr),+] => ({
@@ -262,7 +269,11 @@ impl<'a> Iterator for StrftimeItems<'a> {
                     'x' => recons![num0!(Month), lit!("/"), num0!(Day), lit!("/"),
                                    num0!(YearMod100)],
                     'y' => num0!(YearMod100),
-                    'z' => fix!(TimezoneOffset),
+                    'z' => if is_alternate {
+                        fix!(TimezoneOffsetPermissive)
+                    } else {
+                        fix!(TimezoneOffset)
+                    },
                     '+' => fix!(RFC3339),
                     ':' => match next!() {
                         'z' => fix!(TimezoneOffsetColon),
@@ -368,6 +379,9 @@ fn test_strftime_items() {
     assert_eq!(parse_and_collect("%-e"), [num!(Day)]);
     assert_eq!(parse_and_collect("%0e"), [num0!(Day)]);
     assert_eq!(parse_and_collect("%_e"), [nums!(Day)]);
+    assert_eq!(parse_and_collect("%z"), [fix!(TimezoneOffset)]);
+    assert_eq!(parse_and_collect("%#z"), [fix!(TimezoneOffsetPermissive)]);
+    assert_eq!(parse_and_collect("%#m"), [Item::Error]);
 }
 
 #[cfg(test)]