feat(shfmt): add automatic indentation detection (#481)

* feat(shfmt): automatically detect indentation

* fix(markdown-toc): improve correctness of indentation size calculation

* fix(djlint): improve correctness of indentation size calculation

* feat: add effective `shiftwidth` to `conform.Context`

this also refactors formatters that automatically set indentation level
to use the new shiftwidth context

5 files changed, 17 insertions, 5 deletions

diff --git a/lua/conform/formatters/djlint.lua b/lua/conform/formatters/djlint.lua
index b7a177b..13c966d 100644
--- a/lua/conform/formatters/djlint.lua
+++ b/lua/conform/formatters/djlint.lua
@@ -7,8 +7,7 @@ return {
   },
   command = "djlint",
   args = function(_, ctx)
-    local indent = vim.bo[ctx.buf].tabstop or 4 -- default is 4
-    return { "--reformat", "--indent", indent, "-" }
+    return { "--reformat", "--indent", ctx.shiftwidth, "-" }
   end,
   cwd = util.root_file({
     ".djlintrc",
diff --git a/lua/conform/formatters/markdown-toc.lua b/lua/conform/formatters/markdown-toc.lua
index a7a9694..5e1d80a 100644
--- a/lua/conform/formatters/markdown-toc.lua
+++ b/lua/conform/formatters/markdown-toc.lua
@@ -6,10 +6,10 @@ return {
   },
   command = "markdown-toc",
   stdin = false,
-  args = function(self, ctx)
+  args = function(_, ctx)
     -- use the indentation set in the current buffer, effectively allowing us to
     -- use values from .editorconfig
-    local indent = vim.bo[ctx.buf].expandtab and (" "):rep(vim.bo[ctx.buf].tabstop) or "\t"
+    local indent = vim.bo[ctx.buf].expandtab and (" "):rep(ctx.shiftwidth) or "\t"
     return { "--indent=" .. indent, "-i", "$FILENAME" }
   end,
 }
diff --git a/lua/conform/formatters/shfmt.lua b/lua/conform/formatters/shfmt.lua
index 29b8615..6a75ff9 100644
--- a/lua/conform/formatters/shfmt.lua
+++ b/lua/conform/formatters/shfmt.lua
@@ -5,5 +5,11 @@ return {
     description = "A shell parser, formatter, and interpreter with `bash` support.",
   },
   command = "shfmt",
-  args = { "-filename", "$FILENAME" },
+  args = function(_, ctx)
+    local args = { "-filename", "$FILENAME" }
+    if vim.bo[ctx.buf].expandtab then
+      vim.list_extend(args, { "-i", ctx.shiftwidth })
+    end
+    return args
+  end,
 }
diff --git a/lua/conform/runner.lua b/lua/conform/runner.lua
index 3831198..c0a19cd 100644
--- a/lua/conform/runner.lua
+++ b/lua/conform/runner.lua
@@ -450,6 +450,11 @@ M.build_context = function(bufnr, config, range)
   end
   local filename = vim.api.nvim_buf_get_name(bufnr)
 
+  local shiftwidth = vim.bo[bufnr].shiftwidth
+  if shiftwidth == 0 then
+    shiftwidth = vim.bo[bufnr].tabstop
+  end
+
   -- Hack around checkhealth. For buffers that are not files, we need to fabricate a filename
   if vim.bo[bufnr].buftype ~= "" then
     filename = ""
@@ -482,6 +487,7 @@ M.build_context = function(bufnr, config, range)
     filename = filename,
     dirname = dirname,
     range = range,
+    shiftwidth = shiftwidth,
   }
 end
 
diff --git a/lua/conform/types.lua b/lua/conform/types.lua
index b00c3f0..05a4e4f 100644
--- a/lua/conform/types.lua
+++ b/lua/conform/types.lua
@@ -49,6 +49,7 @@
 ---@field filename string
 ---@field dirname string
 ---@field range? conform.Range
+---@field shiftwidth integer
 
 ---@class (exact) conform.RangeContext : conform.Context
 ---@field range conform.Range