Re: [Patch] Add project.el command to replace symbol at point throughout project

[Juri Linkov]

>> This is needed to handle `read-regexp` in `occur-read-primary-args`
>> that uses the symbol `regexp-history-last` by default.
>
> occur?
>
> read-regexp is called from query-replace-read-from.
>
> Binding read-regexp-defaults-function doesn't seem to work because its use
> is for some reason predicated on (and defaults (symbolp defaults))
> evaluating to non-nil.
>
> And 'read-regexp' is called with nil second argument.

The customizable user option 'read-regexp-defaults-function' was created
for the following problem: by default, 'occur' uses the last history item
as the default value, so 'read-regexp-defaults-function' could be
customized to get a tag at point as the default value of 'occur'.

Exactly the same situation is with 'query-replace-read-from':
by default, it uses the last history item, so changing the value of
'read-regexp-defaults-function' should also affect the query-replace
like in the patch that I sent to Jon.

>> Before finishing this implementation, please answer one question.
>> `query-replace-read-from` uses two minibuffer-reading functions:
>>                  (if regexp-flag
>>                      (read-regexp prompt sym-at-point 'minibuffer-history)
>>                    (read-from-minibuffer
>>                     prompt nil nil nil nil
>>                     (query-replace-read-from-suggestions) t))
>> Do you think the same default with the symbol at point
>> should be used for the non-regexp case with read-from-minibuffer as well?
>> If yes, then we need a different solution that works for both cases.
>
> It doesn't have to be the same. project-query-replace-regexp could bind
> read-regexp-defaults-function, and xref-find-references-and-replace could
> bind something else. But that variable still needs to be created.

xref-find-references-and-replace calls query-replace-read-args
with a non-regexp flag, so I have no idea what new variable
could be created for read-from-minibuffer.  It already uses
'query-replace-read-from-suggestions' where the top value
could be the default.