User with 'administer users' permission receives 406 Not Acceptable: You are not allowed to change your username.

This makes sense.

Fixed and commited in both 6.x and 7.x and attributed to --author="jonathanhunt "

I found my way to this issue because I was getting the 'You are not allowed to change your username' issue when trying to use the user update API method as a user that definitely has 'administer user' permissions.

Unless I'm misunderstanding the intended logic, shouldn't the call to user_access('administer user') permission be negated, so the logic goes like:

IF

the account name is set AND the account name does not equal the current user's name AND the current user does NOT have the 'change own username' permission,

OR

the current user does NOT have the 'administer users' permission

THEN

Return the 'You are not allowed to change your username' error.

usonian, fixed in dex for 6.x and 7.x

This patch did not get correctly applied to 6.x-3.x. There's a set of parens missing, so it's currently

if (isset($account['name']) && $account['name'] != $user->name && !user_access('change own username') || user_access('administer users'))

but should be

if (isset($account['name']) && $account['name'] != $user->name && !(user_access('change own username') || user_access('administer users')))

Remarking as RTBC since it was already accepted.

Woops, fixed.

Reopening this rather than #1419506: User update resource allows name update without 'Change own username' permission because this is more recent commit 614b94a7c08ee67adc557819b2a86c1d630a995e references this issue.

The name-change permission check is correct in the 6.x-3.x branch but it isn't correct in the 7.x-3.x branch.
6.x-3.x logic: services_error if name change and user has NOT ( either 'change own username' OR 'administer users' permission, i.e. neither )
7.x-3.x logic: services_error if name change and user has NOT ( 'change own username' OR NOT 'administer users' permission)

For 7.x-3.x the line reads:

git blame resources/user_resource.inc | grep 'change own username'
614b94a7 (Kyle Browning   2013-03-18 15:35:07 -0700 322)   if (isset($account['name']) && $account['name'] != $account_loaded->name && !(user_access('change own username') || !user_access('administer users'))) {

For 6.x-3.x accordingly:

git blame resources/user_resource.inc | grep 'change own username'
c0c689a8 (h3rj4n          2013-05-11 23:31:20 -0700 309)   if (isset($account['name']) && $account['name'] != $user->name && !(user_access('change own username') || user_access('administer users'))) {

Please find a micro patch attached - i know a test would be great :(

Heres a patch with a test, if green, will commit

green light!