code review 5712045: path/filepath: steer people away from HasPrefix

path/filepath: steer people away from HasPrefix

The strikes against it are:

1. It does not take path boundaries into account.
2. It assumes that Windows==case-insensitive file system
and non-Windows==case-sensitive file system, neither of
which is always true.
3. Comparing ToLower against ToLower is not a correct
implementation of a case-insensitive string comparison.
4. If it returns true on Windows you still don't know how long
the matching prefix is in bytes, so you can't compute what
the suffix is.

[rsc, 2012-02-29 21:04:53]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg/

[rsc, 2012-02-29 21:06:12]

I updated the CL description with the rationale:

	path/filepath: steer people away from HasPrefix
	
	The strikes against it are:
	
	1. It does not take path boundaries into account.
	2. It assumes that Windows==case-insensitive file system
	and non-Windows==case-sensitive file system, neither of
	which is always true.
	3. Comparing ToLower against ToLower is not a correct
	implementation of a case-insensitive string comparison.
	4. If it returns true on Windows you still don't know how long
	the matching prefix is in bytes, so you can't compute what
	the suffix is.

[r, 2012-02-29 21:14:21]

LGTM

[dsymonds, 2012-02-29 21:20:16]

What historical compatibility do we care about enough to preserve
this? Could we drop it and add a gofix to rewrite as
strings.HasPrefix?

[r2, 2012-02-29 21:22:47]

On 01/03/2012, at 8:20 AM, David Symonds wrote:

> What historical compatibility do we care about enough to preserve
> this? Could we drop it and add a gofix to rewrite as
> strings.HasPrefix?

the APIs are frozen. this is far too minor a detail to justify breaking that
rule.

-rob

[rsc, 2012-02-29 21:37:45]

*** Submitted as http://code.google.com/p/go/source/detail?r=aa7ded1d6fab ***

path/filepath: steer people away from HasPrefix

The strikes against it are:

1. It does not take path boundaries into account.
2. It assumes that Windows==case-insensitive file system
and non-Windows==case-sensitive file system, neither of
which is always true.
3. Comparing ToLower against ToLower is not a correct
implementation of a case-insensitive string comparison.
4. If it returns true on Windows you still don't know how long
the matching prefix is in bytes, so you can't compute what
the suffix is.

R=golang-dev, r, dsymonds, r
CC=golang-dev
http://codereview.appspot.com/5712045