Add taplo for formatting TOML files (#373)

Taplo is a very popular formatter and linter for TOML.

https://github.com/tamasfe/taplo

5 files changed, 67 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 26d0944..36b50f5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,7 @@ The format is based on [Keep a Changelog].
 ### Formatters
 * [hurlfmt](https://hurl.dev) for hurl files.
 * [csharpier](https://github.com/belav/csharpier) for C#.
+* [taplo](https://taplo.tamasfe.dev/) for TOML.
 
 ## 4.4.1 (released 2025-05-13)
 ### Enhancements
diff --git a/apheleia-formatters.el b/apheleia-formatters.el
index 8536c2c..581a9a1 100644
--- a/apheleia-formatters.el
+++ b/apheleia-formatters.el
@@ -214,6 +214,7 @@
     (rufo . ("rufo" "--filename" filepath "--simple-exit"))
     (stylua . ("stylua" "-"))
     (rustfmt . ("rustfmt" "--quiet" "--emit" "stdout"))
+    (taplo . ("taplo" "format" "--colors" "never" "-"))
     (terraform . ("terraform" "fmt" "-"))
     (treefmt . ("treefmt" "--stdin" filepath))
     (typstyle . ("typstyle"))
@@ -394,6 +395,7 @@ rather than using this system."
     (terraform-mode . terraform)
     (TeX-latex-mode . latexindent)
     (TeX-mode . latexindent)
+    (toml-ts-mode . taplo)
     (tsx-ts-mode . prettier-typescript)
     (tuareg-mode . ocamlformat)
     (typescript-mode . prettier-typescript)
diff --git a/test/formatters/installers/taplo.bash b/test/formatters/installers/taplo.bash
new file mode 100644
index 0000000..a7dc7f6
--- /dev/null
+++ b/test/formatters/installers/taplo.bash
@@ -0,0 +1 @@
+npm install -g @taplo/cli
diff --git a/test/formatters/samplecode/taplo/in.toml b/test/formatters/samplecode/taplo/in.toml
new file mode 100644
index 0000000..175515a
--- /dev/null
+++ b/test/formatters/samplecode/taplo/in.toml
@@ -0,0 +1,33 @@
+# This is a TOML document.
+
+title = "TOML Example"
+
+[owner]
+name = "Tom Preston-Werner"
+dob = 1979-05-27T07:32:00-08:00 # First class dates
+
+[database]
+server = "192.168.1.1"
+ports = [ 8000, 8001, 8002 ]
+connection_max = 5000
+enabled = true
+
+[servers]
+
+  # Indentation (tabs and/or spaces) is allowed but not required
+  [servers.alpha]
+  ip = "10.0.0.1"
+  dc = "eqdc10"
+
+  [servers.beta]
+  ip = "10.0.0.2"
+  dc = "eqdc10"
+
+[clients]
+data = [ ["gamma", "delta"], [1, 2] ]
+
+# Line breaks are OK when inside arrays
+hosts = [
+  "alpha",
+  "omega"
+]
diff --git a/test/formatters/samplecode/taplo/out.toml b/test/formatters/samplecode/taplo/out.toml
new file mode 100644
index 0000000..77669bd
--- /dev/null
+++ b/test/formatters/samplecode/taplo/out.toml
@@ -0,0 +1,30 @@
+# This is a TOML document.
+
+title = "TOML Example"
+
+[owner]
+name = "Tom Preston-Werner"
+dob = 1979-05-27T07:32:00-08:00 # First class dates
+
+[database]
+server = "192.168.1.1"
+ports = [8000, 8001, 8002]
+connection_max = 5000
+enabled = true
+
+[servers]
+
+# Indentation (tabs and/or spaces) is allowed but not required
+[servers.alpha]
+ip = "10.0.0.1"
+dc = "eqdc10"
+
+[servers.beta]
+ip = "10.0.0.2"
+dc = "eqdc10"
+
+[clients]
+data = [["gamma", "delta"], [1, 2]]
+
+# Line breaks are OK when inside arrays
+hosts = ["alpha", "omega"]