Re: let*: Wrong type argument: stringp, nil

[Hongyi Zhao]

On Wed, Sep 29, 2021 at 10:03 AM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
>
> On Wed, Sep 29, 2021 at 9:43 AM Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
> >
> > On Tue, Sep 28, 2021 at 4:02 PM Yuri Khan <yuri.v.khan@gmail.com> wrote:
> > >
> > > On Tue, 28 Sept 2021 at 10:08, Hongyi Zhao <hongyi.zhao@gmail.com> wrote:
> > >
> > > > Now I'm trying another test code snippet based on the idea posted here 
> > > > [1]:
> > > >
> > > >     (while (not (file-exists-p ".python-version"))
> > > >           (cd "..")
> > > >     ))
> > > >
> > > > But when I test the above code in scratch buffer, it seems to be stuck
> > > > in an endless loop and running there all the time. Any hints for this
> > > > problem?
> > >
> > > You’re not handling the case here that you reached the root directory
> > > without finding a .python-version file.
> > >
> > > You will really get better results if you use locate-dominating-file.
> > > If you’re trying to learn, learn by reading that function. As a bonus,
> > > it does not mess with the buffer’s default directory.
> >
> > I work out the following code snippets using locate-dominating-file,
> > and it works as expected:
> >
> > (defun try/pyvenv-workon ()
> >   (when (locate-dominating-file (buffer-file-name) ".python-version")
>
> The following form should be used here:
>
> (when (and (buffer-file-name) (locate-dominating-file
> (buffer-file-name) ".python-version"))
>
> >       
> > ;https://emacs.stackexchange.com/questions/9474/let-statement-throws-error-on-assigning-a-form-to-a-variable
> >       (let ((file (concat (locate-dominating-file (buffer-file-name)
> > ".python-version") ".python-version")))
> >            (pyvenv-workon (with-temp-buffer
> >                            (insert-file-contents file)
> >                              (nth 0 (split-string (buffer-string))))))))

The complete code for this purpose is as following now:

  (defun try/pyvenv-workon ()
    (when (and (buffer-file-name)
               (locate-dominating-file (buffer-file-name) ".python-version"))
      (let ((file (concat (locate-dominating-file (buffer-file-name)
".python-version") ".python-version")))
        (pyvenv-workon
          (with-temp-buffer
            (insert-file-contents file)
            (nth 0 (split-string (buffer-string))))))))

But I wonder if I can solve this problem by using
`locate-dominating-file' only once?

HZ