Add support for bibtex-mode (#294)

Add support for `bibtex-mode` using emacs native function
`bibtex-reformat`.

5 files changed, 28 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2df4c32..1d0c41f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@ The format is based on [Keep a Changelog].
 ## Unreleased
 ### Formatters
 * Use clang-format for formatting Objective-C/C++ files ([#378]).
+* `bibtex-reformat` for BibTeX files.
 
 ## 4.4.2 (released 2025-11-21)
 ### Bugs fixed
diff --git a/apheleia-formatters.el b/apheleia-formatters.el
index 65c0b15..928dcbb 100644
--- a/apheleia-formatters.el
+++ b/apheleia-formatters.el
@@ -29,6 +29,7 @@
                  (apheleia-formatters-indent
                   "--tab" "--indent-size" 'sh-basic-offset)
                  "-"))
+    (bibtex . apheleia-reformat-bibtex-buffer)
     (black . ("black"
               (when (apheleia-formatters-extension-p "pyi") "--pyi")
               (apheleia-formatters-fill-column "--line-length")
@@ -318,6 +319,7 @@ rather than using this system."
     (bash-ts-mode . shfmt)
     (bazel-mode . buildifier)
     (beancount-mode . bean-format)
+    (bibtex-mode . bibtex)
     (c++-ts-mode . clang-format)
     (caddyfile-mode . caddyfmt)
     (cc-mode . clang-format)
@@ -1223,6 +1225,20 @@ For more implementation detail, see
       (indent-region (point-min) (point-max)))
     (funcall callback)))
 
+(cl-defun apheleia-reformat-bibtex-buffer
+    (&key buffer scratch callback &allow-other-keys)
+  "Format a Bibtex BUFFER.
+Use SCRATCH as a temporary buffer and CALLBACK to apply the
+transformation.
+
+For more implementation detail, see
+`apheleia--run-formatter-function'."
+  (with-current-buffer scratch
+    (funcall (with-current-buffer buffer major-mode))
+    (when (fboundp 'bibtex-reformat)
+      (bibtex-reformat))
+    (funcall callback)))
+
 (cl-defun apheleia--run-formatters
     (formatters buffer remote callback &optional stdin)
   "Run one or more code formatters on the current buffer.
diff --git a/test/formatters/installers/bibtex.bash b/test/formatters/installers/bibtex.bash
new file mode 100644
index 0000000..97dbfb0
--- /dev/null
+++ b/test/formatters/installers/bibtex.bash
@@ -0,0 +1 @@
+# Nothing to do here, this formatter is pure Emacs!
diff --git a/test/formatters/samplecode/bibtex/in.bib b/test/formatters/samplecode/bibtex/in.bib
new file mode 100644
index 0000000..fcfbd6f
--- /dev/null
+++ b/test/formatters/samplecode/bibtex/in.bib
@@ -0,0 +1,5 @@
+@article{key,
+  title={An Article},
+ author = {John  Doe},
+year=2020
+}
diff --git a/test/formatters/samplecode/bibtex/out.bib b/test/formatters/samplecode/bibtex/out.bib
new file mode 100644
index 0000000..36da836
--- /dev/null
+++ b/test/formatters/samplecode/bibtex/out.bib
@@ -0,0 +1,5 @@
+@article{key,
+  title =        {An Article},
+  author =       {John Doe},
+  year =         2020
+}