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Inferior-haskell: do not insert repeated prompts. #1806

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Inferior-haskell: do not insert repeated prompts. #1806

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54 changes: 53 additions & 1 deletion inf-haskell.el
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Original file line number Diff line number Diff line change
Expand Up @@ -113,6 +113,25 @@ The format should be the same as for `compilation-error-regexp-alist'.")
correctly interpret multi-line input even when modules are
imported.")

(defconst inferior-haskell-cont-prompt-regexp
"^[[:alnum:].*_() |λ]*| "
"Continuation prompt rexep.
Used to remove them from the output by the comint preoutput filter. See
`inferior-haskell-remove-extra-prompts'.

This should be a similar regexp as `haskell-prompt-regexp', but it usually
ends with \"| \" instead of \"> \".")

(defconst inferior-haskell-maybe-cont-prompt-regexp
"^[[:alnum:].*_() |λ]*[>|] "
"A continuation or non-continuation prompt regexp.
This should match any prompt, a continuation or a common prompt. This regexp
should be similar to `haskell-prompt-regexp' and
`inferior-haskell-cont-prompt-regex' as it should match both.

It is used to remove multiple prompts on the comint preoutput filter. See
`inferior-haskell-remove-extra-prompts'.")

;;; TODO
;;; -> Make font lock work for strings, directories, hyperlinks
;;; -> Make font lock work for key words???
Expand Down Expand Up @@ -161,7 +180,40 @@ imported.")
(define-key map keys (lookup-key compilation-minor-mode-map keys)))
(add-to-list 'minor-mode-overriding-map-alist
(cons 'compilation-minor-mode map))))
(add-hook 'inferior-haskell-hook 'inferior-haskell-init))
(add-hook 'inferior-haskell-hook 'inferior-haskell-init)

;; Avoid multiple prompts at the end of the output
(add-hook 'comint-preoutput-filter-functions
#'inferior-haskell-remove-extra-prompts nil t))

(defun inferior-haskell-remove-extra-prompts (str)
"Remove any extra Haskell-prompts from STR.
Remove multiple prompts from STR. All prompts indicating continuation are
completely removed. Only remain the last non-continuantion prompt.

Examples:
The input \"Prelude> Prelude> \" will return \"Prelude> \".
The input \"Prelude| Prelude| \" will return \"\".

These kind of output are usually produced by the multiple line input (i.e. when
using \":{ ... :}\" code in the GHCi interpreter). Sometimes, comint would note
filter the prompts out. For this reason, this function shoud be added to the
hook `comint-preoutput-filter-functions', to be executed before comint insert
STR to the buffer.

Some libraries, such as ob-haskell.el, considers the multilple prompts as part
of the evaluation output. Moreover, it does not provide any information to the
user. Removing these prompts provides a better reading and less code for parsing
the output."
(let ((last-match nil))
(while (string-match inferior-haskell-maybe-cont-prompt-regexp str)
(setq last-match (match-string 0 str))
(setq str (substring str (match-end 0))))
;; Remove prompt-cont if it is the last one.
(if (or (null last-match)
(string-match inferior-haskell-cont-prompt-regexp last-match))
str
(concat last-match str))))

(defvar inferior-haskell-buffer nil
"The buffer in which the inferior process is running.")
Expand Down