Sorry, couldn't guess a value for fsharp-indent-offset

[r-moeritz]

Sorry, couldn't guess a value for fsharp-indent-offset

[rneatherway]

Hi Ralph,

This shouldn't be related to whether or not you have started fsi yet. The offset guess is just some elisp that inspects the buffer you are opening to try and work out how many spaces you are using for indentation. It defaults to 2, and that's what you get if the offset guess fails.

Please try checking the file you had the message with to make sure it is in fact independent of the fsi status.

[r-moeritz]

Here's my scenario:

    1. Launch Emacs
    2. Visit a new F# file. Bam! Error: "Sorry, couldn't guess a value for fsharp-indent-offset"
    3. Close Emacs
    4. Launch Emacs
    5. M-x run-fsharp
    6. Visit a new F# file. No error.

Date: Wed, 23 Jan 2013 02:41:28 -0800
From: [email protected]
To: [email protected]
CC: [email protected]
Subject: Re: [fsharpbinding] Sorry, couldn't guess a value for
fsharp-indent-offset (#80)

Hi Ralph,

This shouldn't be related to whether or not you have started fsi yet.
The offset guess is just some elisp that inspects the buffer you are
opening to try and work out how many spaces you are using for
indentation. It defaults to 2, and that's what you get if the offset
guess fails.

Please try checking the file you had the message with to make sure it
is in fact independent of the fsi status.

—
Reply to this email directly or view it on
GitHubhttps://github.com//issues/80#issuecomment-12590052.

[rneatherway]

I just installed from melpa and got fsharp-mode-20130117.1805 in my .emacs.d/elpa directory.

1. Launched Emacs
2. C-x C-f test.fs (visit a new file)
3. No error

So, are we using the same version of the mode? Or are we doing something different?

[r-moeritz]

Checked in .emacs.d/elpa and I have the same version of fsharp-mode as you. Running Emacs 24.2 on Windows 7 x64. Followed the same steps as you and got:

  signal(error ("Sorry, couldn't guess a value for fsharp-indent-offset"))
  error("Sorry, couldn't guess a value for fsharp-indent-offset")
  fsharp-guess-indent-offset()
  fsharp-mode()
  set-auto-mode-0(fsharp-mode nil)
  set-auto-mode()
  normal-mode(t)
  after-find-file(t t)
  find-file-noselect-1(#<buffer test.fs> "c:/test.fs" nil nil "c:/test.fs" nil)
  find-file-noselect("c:/test.fs" nil nil t)
  find-file("c:/test.fs" t)
  call-interactively(find-file nil nil)

I've tried using Edebug to debug the code but can't seem to get it to stop execution; I'm probably doing it wrong since I've never used Edebug before.

[r-moeritz]

Okay, I've managed to debug fsharp-guess-indent-offset. Observations as inline comments below:

   (while (not (or found (eobp)))
      ;; This is not executed because (eobp) evaluates to t since the buffer is empty.
      (when (and (re-search-forward fsharp-block-opening-re nil 'move)
                 (not (fsharp-in-literal restart)))
        (setq restart (point))
        (fsharp-goto-initial-line)
        (if (fsharp-statement-opens-block-p)
            (setq found t)
          (goto-char restart))))
    (unless found
      ;; Execution continues here.
      (goto-char start)
      (fsharp-goto-initial-line)
      (while (not (or found (bobp)))
        ;; Execution doesn't reach here because (bobp) evaluates to t.
        (setq found (and
                     (re-search-backward fsharp-block-opening-re nil 'move)
                     (or (fsharp-goto-initial-line) t) ; always true -- side effect
                     (fsharp-statement-opens-block-p)))))
    (setq colon-indent (current-indentation)
          found (and found (zerop (fsharp-next-statement 1))) ;; nil - (fsharp-next-statement 1) evaluates to 1
          new-value (- (current-indentation) colon-indent))
    (goto-char start)
    (if (not found)
        ;; Execution continues here.
        (error "Sorry, couldn't guess a value for fsharp-indent-offset")

[rneatherway]

I also did a bit of debugging and I found that it ends up calling
parse-partial-sexp to try and find the nesting level. It then uses the
number of encountered parentheses to decide whether it is in a continuation
line. I can't see why I don't also get the error as a result -- this code
predates my involvement.

For now, I recommend following the advice in the docstring of
fsharp-smart-indentation:

Note that both these settings occur after fsharp-mode-hook' is run, so if you want to defeat the automagic configuration, you must also setfsharp-smart-indentation' to nil in your `fsharp-mode-hook'.

On Wed, Jan 23, 2013 at 12:15 PM, Ralph Möritz [email protected]:

Okay, I've managed to debug fsharp-guess-indent-offset. Observations as
inline comments below:

(while (not (or found (eobp)))
;; This is not executed because (eobp) evaluates to t since the buffer is empty.
(when (and (re-search-forward fsharp-block-opening-re nil 'move)
(not (fsharp-in-literal restart)))
(setq restart (point))
(fsharp-goto-initial-line)
(if (fsharp-statement-opens-block-p)
(setq found t)
(goto-char restart))))
(unless found
;; Execution continues here.
(goto-char start)
(fsharp-goto-initial-line)
(while (not (or found (bobp)))
;; Execution doesn't reach here because (bobp) evaluates to t.
(setq found (and
(re-search-backward fsharp-block-opening-re nil 'move)
(or (fsharp-goto-initial-line) t) ; always true -- side effect
(fsharp-statement-opens-block-p)))))
(setq colon-indent (current-indentation)
found (and found (zerop (fsharp-next-statement 1))) ;; nil - (fsharp-next-statement 1) evaluates to 1
new-value (- (current-indentation) colon-indent))
(goto-char start)
(if (not found)
;; Execution continues here.
(error "Sorry, couldn't guess a value for fsharp-indent-offset")

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/80#issuecomment-12592987.

[rneatherway]

More information: at fsharp-mode.el:221, the call:

  (if (and (fsharp-safe (fsharp-guess-indent-offset))

is wrapped with the macro fsharp-safe, which is defined at fsharp-mode-indent.el:218:

(defmacro fsharp-safe (&rest body)
  "Safely execute BODY, return nil if an error occurred."
  `(condition-case nil
       (progn ,@ body)
     (error nil)))

When the files are byte-compiled (as the packaged versions end up being), it doesn't seem to catch the error. I think that the fsharp-guess-indent-offset function has not worked for a long time, but I never noticed because it is always just caught by this macro. I am not an elisp expert, and I don't know why this behaviour is occuring. Installing the package and then deleting the .elc files leaves me in a situation where this error is not thrown, but a) it should work without intervention and b) I want to understand why there is this difference between compiled and interpreted code.

[rneatherway]

OK, it seems that fsharp-mode.el should have been requireing fsharp-mode-indent so that it had access to this macro. Strange that the require further down was not sufficient. Anyway, this is now fixed in the repository. Next time melpa updates, you should be able to install a version of the package without this bad behaviour. The guessing code still needs investigating to find out if it ever worked though! I'll leave this issue open until we have observed the melpa package behaving better.

[r-moeritz]

Great, it seems after upgrading to the latest MELPA fsharp-mode visiting a new F# file no longer leads to this error. Thanks!

Date: Wed, 23 Jan 2013 10:32:09 -0800
From: [email protected]
To: [email protected]
CC: [email protected]
Subject: Re: [fsharpbinding] Sorry, couldn't guess a value for fsharp-indent-offset (#80)

OK, it seems that fsharp-mode.el should have been requireing fsharp-mode-indent so that it had access to this macro. Strange that the require further down was not sufficient. Anyway, this is now fixed in the repository. Next time melpa updates, you should be able to install a version of the package without this bad behaviour. The guessing code still needs investigating to find out if it ever worked though! I'll leave this issue open until we have observed the melpa package behaving better.

          —

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