strings: Title function incorrectly handles word breaks

[arbrown]

This is a known bug, but there is no issue (that I could find) for it.

https://code.google.com/p/go/source/browse/src/pkg/strings/strings.go#485

The Title function should return a new copy of a string with each word capitalized (or,
more accurately, the first rune of each word converted to title case, which can
occasionally differ from Upper Case.)

The following sample program illustrates the incorrect current behavior:
http://play.golang.org/p/u8AJs-95-g
The Title function simply assumes any separator character (like the apostrophe, in this
case) is a word boundary.  The reality is somewhat more complicated.  For reference, see:

http://www.unicode.org/reports/tr29/
http://unicode.org/Public/UNIDATA/auxiliary/WordBreakTest.html

[robpike]

Comment 1:

It's documented in the code:
func Title(s string) string
    Title returns a copy of the string s with all Unicode letters that begin
    words mapped to their title case.
    BUG: The rule Title uses for word boundaries does not handle Unicode
    punctuation properly.
Unlikely to be fixed. Instead, perhaps the documentation should refer to a proper
implementation once it lands in go.text.
Not exactly working as intended, but working about as well as it ever will.

Labels changed: added priority-later, documentation, removed priority-triage.

Status changed to Accepted.

[rsc]

Comment 2:

Labels changed: added go1.3maybe.

[dsymonds]

Comment 3:

Owner changed to @robpike.

[rsc]

Comment 4:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 5:

Labels changed: added repo-main.

[robpike]

Not going to be fixed in 1.8.

[robpike]

This is unplanned and will stay that way indefinitely. There are no plans to fix it. Please do not tag it for each Go release and do not assign it to me.