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; Improve documentation of handling errors

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* doc/lispref/control.texi (Processing of Errors): Document that
pending input is discarded upon errors.  (Bug#79510)
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Eli Zaretskii 2025-09-26 09:13:10 +03:00
parent 307f465f7b
commit 704fab0452
1 changed files with 12 additions and 4 deletions
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16
doc/lispref/control.texi
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@ -2034,7 +2034,8 @@ concept of continuable errors.
@subsubsection How Emacs Processes Errors
@cindex processing of errors
When an error is signaled, @code{signal} searches for an active
When a Lisp program signals an error, it calls the function
@code{signal}, which searches for an active
@dfn{handler} for the error. A handler is a sequence of Lisp
expressions designated to be executed if an error happens in part of the
Lisp program. If the error has an applicable handler, the handler is
@ -2044,9 +2045,16 @@ established it; all functions called within that @code{condition-case}
have already been exited, and the handler cannot return to them.
If there is no applicable handler for the error, it terminates the
current command and returns control to the editor command loop. (The
command loop has an implicit handler for all kinds of errors.) The
command loop's handler uses the error symbol and associated data to
current command, flushes all pending unprocessed input events
(@pxref{Input Events})@footnote{
Pending input is discarded because the user could have typed something
in advance under the assumption that execution will proceed without
errors, so keeping these input events would cause unintended
consequences, like inserting stray characters into an unrelated buffer
or execution of some unintended command.
}, and returns control to the editor command loop.
(The command loop has an implicit handler for all kinds of errors.) The
command loop's handler then uses the error symbol and associated data to
print an error message. You can use the variable
@code{command-error-function} to control how this is done: