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Emacs: substitute version 0.2.0

Substitute is a set of commands that perform text replacement (i) throughout the buffer, (ii) limited to the current definition (per narrow-to-defun), (iii) from point to the end of the buffer, and (iv) from point to the beginning of the buffer.

These substitutions are meant to be as quick as possible and, as such, differ from the standard query-replace (which I still use). The provided commands prompt for substitute text and perform the substitution outright, without moving the point.

Below are the release notes.

The package has been in a stable state since its inception, to the point where I thought I had already formalised its latest version as a release…

The value proposition of substitute is shown in the video I did for it: https://protesilaos.com/codelog/2023-01-16-emacs-substitute-package-demo/.

Notable refinements:

  • It is now possible to substitute a target with an empty string. We could not do that with read-string function that was originally in use, as the empty input is automatically interpreted as the value of the DEFAULT-VALUE argument that read-string gets. This is standard for most Emacs minibuffer interactions, though in our case it makes sense to accept an empty string that is distinct from the default value, as we may, e.g., want to remove a prefix from a target. Thanks to Kostas Andreadis for discussing this with me in issue 2 on the GitHub mirror as well as pull request 3:

  • Target strings that contain escape sequences do not confuse Substitute anymore. The substitution will be performed as expected. Thanks to Kostas Andreadis for the contribution, which was done in pull request 3 on the GitHub mirror: https://github.com/protesilaos/substitute/pull/3.

  • Calling undo after a substitution no longer moves the point. This is consistent with the behaviour of Substitute when it replaces the target text. Thanks to Ed Tavinor for the patch, which was done via a private channel.

  • Normally, Substitute will retain the letter casing of the underlying target. This means that if it is replacing “hello” with “hey” and there is a “HELLO” instance, it will replace it with “HEY”. This is often the desired behaviour. Though now all Substitute commands accept an optional prefix argument (C-u with default key bindings), which is interpreted as a “fixed case” substitution: the user input is applied as-is, regardless of the underlying letter casing. To always have fixed letter casing, set the user option substitute-fixed-letter-case to a non-nil value. Doing so is the same as always calling the commands with a prefix argument. Thanks to revrari for bringing this matter to my attention in issue 4 on the GitHub mirror: https://github.com/protesilaos/substitute/issues/4.

  • Substitute will not even try to perform its task in a read-only buffer. Thanks to ersi-dnd for bringing this matter to my attention. This was done in issue 6 on the GitHub mirror: https://github.com/protesilaos/substitute/issues/6.

  • The built-in subr-x library is explicitly required to avoid byte compilation warnings. Thanks to Chunye Wang for the contribution, which was done in pull request 1 on the GitHub mirror: https://github.com/protesilaos/substitute/pull/1.

The code contributions from Ed Tavinor, Kostas Andreadis, and Chunye Wang are small, meaning that their respective authors do not need to assign copyright to the Free Software Foundation.