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= noflet - Local function decoration =
{{{noflet}}} is dynamic, local, advice for Emacs-Lisp code.
{{{noflet}}} also has an Emacs indentation function for {{{flet}}}
like macros.
It's great for test code when you need to mock another function.
This is useful for definining functions that overide a base definition
in some way. You get access to the original (before you re-defined it)
function through a different name.
Use it like this:
{{{
(noflet ((find-file-noselect (file-name)
(if (string-match-p "^#.*" file-name)
(this-fn "/tmp/mytest")
(this-fn file-name)))
(expand-file-name (file-name &optional thing)
(if (string-match-p "^#.*" file-name)
(concat "/tmp" (file-name-as-directory
(substring file-name 1)))
(funcall this-fn file-name thing))))
(expand-file-name "#/thing"))
}}}
This specifies that two functions should be overridden:
* {{{find-file-noselect}}} is changed so that if the file-name begins with {{{#}}} a different file-name altogether is opened
* {{{expand-file-name}}} is changed so that if the file-name begins with {{{#}}} it's resolved via {{{/tmp}}}
In both cases {{{this-fn}}} is used to access the original function
definition of these common Emacs functions.
=== Decorating results ===
{{{noflet}}} can also be used to decorate results, just like
{{{around-advice}}}:
{{{
(noflet ((find-file (file-name &optional wildcards)
(let ((result (funcall this-fn file-name wildcards)))
(with-current-buffer result
(setq some-buffer-local "special"))
result)))
(with-current-buffer (find-file "~/some-file")
(message "buffer local var is: %s" some-buffer-local)))
}}}
This overrides {{{find-file}}} to set a local variable. There are
surely better ways to do it than this but it illustrates the point.
=== Lexical version ===
Because we include a good indenting function we also include a lexical
{{{flet}}}. It's just a wrapper for {{{cl-flet}}}.
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