From 364a10aa54acd8de71a10d1ab98d059a27f26460 Mon Sep 17 00:00:00 2001 From: Spencer Baugh Date: Tue, 5 Sep 2023 15:40:06 -0400 Subject: [PATCH] Correctly handle common prefixes in substring completion Substring completion would previously not complete the longest common substring if that substring was a prefix of all the completion alternatives. Now it does. An explanation of this bug Substring completion is implemented by passing the `prefix' symbol as part of the pattern passed to completion-pcm--merge-completions. This symbol is supposed to cause completion-pcm--merge-completions to "grow" a completion of a common substring only from the "right" of the symbol (a common suffix), not from the "left" of the symbol (a common prefix). Yes, this is the opposite of what the name `prefix' would imply. When processing a symbolic element of the pattern, completion-pcm--merge-completions first finds the common prefix of all the completions in that part of the pattern (using try-completion). Then for `prefix' and other elements which want to complete a common suffix, the common prefix is removed from each element and then the common suffix is calculated with completion--common-suffix. If the common prefix covers the entirety of all the alternatives (i.e. when "unique" is true in the code), it's also a common suffix. In that case, the common suffix calculation (if it runs) is basically a no-op which will produce an empty string, since we removed the common prefix before running it. Before this change, `prefix' elements would unconditionally discard the common prefix, which produced the wrong result in the case that common prefix == common suffix. For example: (completion-pcm--merge-completions '("ab" "ab") '(prefix "b")) -> ("b") Now we detect this situation and include the common prefix in this case for `prefix' elements. Then we get: (completion-pcm--merge-completions '("ab" "ab") '(prefix "b")) -> ("b" "a") which is correct. * lisp/minibuffer.el (completion-pcm--merge-completions): Don't ignore a common suffix in a `prefix' pattern element when it's also a common prefix. * test/lisp/minibuffer-tests.el (completion-substring-test-5): Add a test. --- lisp/minibuffer.el | 4 +++- test/lisp/minibuffer-tests.el | 13 +++++++++++++ 2 files changed, 16 insertions(+), 1 deletion(-) diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el index 35b359a75e2..ac054da61d2 100644 --- a/lisp/minibuffer.el +++ b/lisp/minibuffer.el @@ -4038,7 +4038,9 @@ completion-pcm--merge-completions (unique (or (and (eq prefix t) (setq prefix fixed)) (and (stringp prefix) (eq t (try-completion prefix comps)))))) - (unless (or (eq elem 'prefix) + ;; if the common prefix is unique, it also is a common + ;; suffix, so we should add it for `prefix' elements + (unless (or (and (eq elem 'prefix) (not unique)) (equal prefix "")) (push prefix res)) ;; If there's only one completion, `elem' is not useful diff --git a/test/lisp/minibuffer-tests.el b/test/lisp/minibuffer-tests.el index ff58d35eb3e..4f92d7f841c 100644 --- a/test/lisp/minibuffer-tests.el +++ b/test/lisp/minibuffer-tests.el @@ -298,6 +298,19 @@ completion-substring-test-4 "jab" '("dabjabstabby" "many") nil 3))) 6))) +(ert-deftest completion-substring-test-5 () + ;; merge-completions needs to work correctly when + (should (equal + (completion-pcm--merge-completions '("ab" "sab") '(prefix "b")) + '("b" "a" prefix))) + (should (equal + (completion-pcm--merge-completions '("ab" "ab") '(prefix "b")) + '("b" "a"))) + ;; substring completion should successfully complete the entire string + (should (equal + (completion-substring-try-completion "b" '("ab" "ab") nil 0) + '("ab" . 2)))) + (ert-deftest completion-flex-test-1 () ;; Fuzzy match (should (equal -- 2.39.3