216895 - Preferences type cannot be changed after clearing

Status: NEW

(Core :: Preferences: Backend, defect, P5)

Description

[Met - Martin Hassman]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.0; cs-CZ; rv:1.4) Gecko/20030624
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; cs-CZ; rv:1.4) Gecko/20030624

When you clear some preferences value and try to set new value (but with
different type) this raises an exception. You have to restart Mozilla to change
preferences type.

In the documentation in nsIPrefBranch.idl for the clearing method
"ClearUserPref()" is:
----------
   * Called to clear a user set value from a specific preference. This will, in
   * effect, reset the value to the default value. If no default value exists
   * the preference will cease to exist.
----------

But the behaviour of the ClearUserPref is different. "If no default value exists
the preference is cleared but exists until Mozilla restart".

Reproducible: Always

Steps to Reproduce:
1. Create some pref value e.g. bool type
2. Clear this value
3. Try to set another type to this (char or int)

Actual Results:  
Raises an exception.

Expected Results:  
Set new preferences value with the new type.

I have same results with nsIPrefBranch and nsIPref interfaces.

For details I am going to include an example in the attachment.

Comment 1

[Met - Martin Hassman]

Attachment: Example for bug reproducing

Here is an example:

It creates "onlytest.debug.test1" Bool pref value, then clear it and try to
write "onlytest.debug.test1" Int pref value, this raises an exception, because
Mozilla remember the old type (Bool) until restart.

Comment 2

[[e-mail]]

Reassigning to someone who might actually read bugmail.

Comment 3

[[e-mail]]

I was wrong :-( Sorry for the SPAM

Comment 4

[Christopher Aillon (sabbatical, not receiving bugmail)]

See
http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/modules/libpref/src/prefapi.cpp&rev=3.139&mark=580-585#572

Comment 5

[Steve Chapel]

*** Bug 253619 has been marked as a duplicate of this bug. ***

Comment 6

[Serge Gautherie (:sgautherie)]

(Filter "spam" on 'prefs-nobody-20080612'.)