feat: add support for yew-fmt (#398)

* feat: add support for yew-fmt

Should close #314 :)

* refactor: copy rustfmt to yew-fmt

* fix: use correct default_edition

* refactor: extract Cargo.toml parsing into utility function

* refactor: yew-fmt doesn't rely directly on rustfmt definition

---------

Co-authored-by: Steven Arcangeli <stevearc@stevearc.com>

5 files changed, 42 insertions, 20 deletions

diff --git a/README.md b/README.md
index d33421a..d9ce5f9 100644
--- a/README.md
+++ b/README.md
@@ -319,6 +319,7 @@ You can view this list in vim with `:help conform-formatters`
 - [yamlfix](https://github.com/lyz-code/yamlfix) - A configurable YAML formatter that keeps comments.
 - [yamlfmt](https://github.com/google/yamlfmt) - yamlfmt is an extensible command line tool or library to format yaml files.
 - [yapf](https://github.com/google/yapf) - Yet Another Python Formatter.
+- [yew-fmt](https://github.com/schvv31n/yew-fmt) - Code formatter for the Yew framework.
 - [yq](https://github.com/mikefarah/yq) - YAML/JSON processor
 - [zigfmt](https://github.com/ziglang/zig) - Reformat Zig source into canonical form.
 - [zprint](https://github.com/kkinnear/zprint) - Formatter for Clojure and EDN.
diff --git a/doc/conform.txt b/doc/conform.txt
index a4981d0..834822e 100644
--- a/doc/conform.txt
+++ b/doc/conform.txt
@@ -373,6 +373,7 @@ FORMATTERS                                                    *conform-formatter
 `yamlfmt` - yamlfmt is an extensible command line tool or library to format yaml
           files.
 `yapf` - Yet Another Python Formatter.
+`yew-fmt` - Code formatter for the Yew framework.
 `yq` - YAML/JSON processor
 `zigfmt` - Reformat Zig source into canonical form.
 `zprint` - Formatter for Clojure and EDN.
diff --git a/lua/conform/formatters/rustfmt.lua b/lua/conform/formatters/rustfmt.lua
index 62d2d78..e33fb86 100644
--- a/lua/conform/formatters/rustfmt.lua
+++ b/lua/conform/formatters/rustfmt.lua
@@ -1,15 +1,4 @@
----@param manifest string
----@return nil|string
-local function parse_edition(manifest)
-  for line in io.lines(manifest) do
-    if line:match("^edition *=") then
-      local edition = line:match("%d+")
-      if edition then
-        return edition
-      end
-    end
-  end
-end
+local util = require("conform.util")
 
 ---@type conform.FileFormatterConfig
 return {
@@ -24,14 +13,7 @@ return {
   },
   args = function(self, ctx)
     local args = { "--emit=stdout" }
-    local edition
-    local manifest = vim.fs.find("Cargo.toml", { upward = true, path = ctx.dirname })[1]
-    if manifest then
-      edition = parse_edition(manifest)
-    end
-    if not edition then
-      edition = self.options.default_edition
-    end
+    local edition = util.parse_rust_edition(ctx.dirname) or self.options.default_edition
     table.insert(args, "--edition=" .. edition)
 
     return args
diff --git a/lua/conform/formatters/yew-fmt.lua b/lua/conform/formatters/yew-fmt.lua
new file mode 100644
index 0000000..f441fdf
--- /dev/null
+++ b/lua/conform/formatters/yew-fmt.lua
@@ -0,0 +1,21 @@
+local util = require("conform.util")
+
+---@type conform.FileFormatterConfig
+return {
+  meta = {
+    url = "https://github.com/schvv31n/yew-fmt",
+    description = "Code formatter for the Yew framework.",
+  },
+  command = "yew-fmt",
+  options = {
+    -- The default edition of Rust to use when no Cargo.toml file is found
+    default_edition = "2021",
+  },
+  args = function(self, ctx)
+    local args = { "--emit=stdout" }
+    local edition = util.parse_rust_edition(ctx.dirname) or self.options.default_edition
+    table.insert(args, "--edition=" .. edition)
+
+    return args
+  end,
+}
diff --git a/lua/conform/util.lua b/lua/conform/util.lua
index 2f334d0..fe2a306 100644
--- a/lua/conform/util.lua
+++ b/lua/conform/util.lua
@@ -187,4 +187,21 @@ M.buf_get_changedtick = function(bufnr)
   end
 end
 
+---Parse the rust edition from the Cargo.toml file
+---@param dir string
+---@return string?
+M.parse_rust_edition = function(dir)
+  local manifest = vim.fs.find("Cargo.toml", { upward = true, path = dir })[1]
+  if manifest then
+    for line in io.lines(manifest) do
+      if line:match("^edition *=") then
+        local edition = line:match("%d+")
+        if edition then
+          return edition
+        end
+      end
+    end
+  end
+end
+
 return M