fix: pass through env config

CHANGELOG.md

@@ -1,5 +1,15 @@
 # Changelog
 
+## Unreleased
+
+### Bug fixes
+
+- [CanonicalTailwind.Config] Pass a tailwind profile's `:env` to `tailwindcss canonicalize`. A CSS entrypoint can depend on environment that only the profile carries, such as `NODE_PATH`. ([#11](https://github.com/aptinio/canonical_tailwind/issues/11))
+
+### Enhancements
+
+- [CanonicalTailwind.Config] Add `:env` for projects that configure `:binary` rather than a tailwind profile.
+
 ## v0.3.3 (2026-09-30)
 
 ### Bug fixes

README.md

@@ -181,6 +181,10 @@ determining canonical forms.
 - **`:cd`** — working directory for the CLI process (defaults to the
   project root)
 - **`:input`** — CSS entrypoint, relative to `:cd`
+- **`:env`** — environment for the CLI process, as a map or keyword
+  list; a list value is joined with the OS path separator (e.g.
+  `%{"NODE_PATH" => ["deps", "_build/dev"]}`). `NODE_PATH` requires
+  tailwindcss 4.2.3 or newer
 
 ```elixir
 # .formatter.exs

lib/canonical_tailwind/canonicalizer/worker.ex

@@ -16,12 +16,20 @@ defmodule CanonicalTailwind.Canonicalizer.Worker do
       :use_stdio,
       {:line, 65_536},
       {:cd, to_charlist(config.cd)},
+      {:env, env_charlists(config.env)},
       args: config.args
     ]
 
     Port.open({:spawn_executable, config.binary}, port_opts)
   end
 
+  defp env_charlists(env) do
+    Enum.map(env, fn
+      {name, nil} -> {to_charlist(name), false}
+      {name, value} -> {to_charlist(name), to_charlist(value)}
+    end)
+  end
+
   @impl GenServer
   def handle_call({:canonicalize, class_string}, _from, state) do
     Port.command(state.port, [class_string, ?\n])

lib/canonical_tailwind/config.ex

@@ -7,7 +7,7 @@ defmodule CanonicalTailwind.Config do
   @minimum_version Version.parse!("4.2.2")
   @non_profile_keys [:version, :version_check, :path, :target, :cacerts_path]
 
-  @enforce_keys [:args, :binary, :cd, :timeout]
+  @enforce_keys [:args, :binary, :cd, :env, :timeout]
   defstruct @enforce_keys
 
   def resolve!(formatter_opts, tailwind_env) do
@@ -17,6 +17,7 @@ defmodule CanonicalTailwind.Config do
     {binary, profile_config} = resolve_binary!(opts, tailwind_env)
     cd = resolve_cd!(opts, profile_config)
     validate_cd!(cd)
+    env = resolve_env(opts, profile_config)
     binary = Path.expand(binary, cd)
     validate_binary!(binary)
     ensure_minimum_version!(binary, opts)
@@ -35,6 +36,7 @@ defmodule CanonicalTailwind.Config do
       args: args,
       binary: binary,
       cd: cd,
+      env: env,
       timeout: timeout
     }
   end
@@ -209,6 +211,26 @@ defmodule CanonicalTailwind.Config do
     end
   end
 
+  defp resolve_env(opts, profile_config) do
+    env =
+      case Keyword.get(opts, :env) do
+        nil -> profile_config[:env] || %{}
+        env -> env
+      end
+
+    Map.new(env, fn
+      {name, value} when is_list(value) -> {name, Enum.join(value, path_sep())}
+      other -> other
+    end)
+  end
+
+  defp path_sep do
+    case :os.type() do
+      {:win32, _} -> ";"
+      _ -> ":"
+    end
+  end
+
   defp validate_binary!(binary) do
     if !System.find_executable(binary) do
       raise ArgumentError,

test/canonical_tailwind/canonicalizer/worker_test.exs

@@ -48,6 +48,7 @@ defmodule CanonicalTailwind.Canonicalizer.WorkerTest do
       args: ["canonicalize", "--stream"],
       binary: Path.expand("../../fixtures/#{fixture}", __DIR__),
       cd: File.cwd!(),
+      env: %{},
       timeout: Keyword.fetch!(opts, :timeout)
     }
 

test/canonical_tailwind/canonicalizer_test.exs

@@ -97,6 +97,48 @@ defmodule CanonicalTailwind.CanonicalizerTest do
              "p-4 min-[40rem]:flex"
   end
 
+  test "runs the CLI with the configured env" do
+    binary = Path.expand("../fixtures/tailwindcss-echoes-node-path", __DIR__)
+
+    opts = [
+      canonical_tailwind: [
+        binary: binary,
+        cd: File.cwd!(),
+        env: %{"NODE_PATH" => ["deps", "_build/dev"]}
+      ]
+    ]
+
+    # The fixture CLI ignores the classes and answers with its own NODE_PATH, so
+    # the response is the joined value as the spawned process received it.
+    assert Canonicalizer.canonicalize("p-0 flex", opts) == "deps:_build/dev"
+  end
+
+  test "unsets an inherited env variable in the CLI without changing the parent" do
+    node_path = System.get_env("NODE_PATH")
+
+    on_exit(fn ->
+      if node_path do
+        System.put_env("NODE_PATH", node_path)
+      else
+        System.delete_env("NODE_PATH")
+      end
+    end)
+
+    System.put_env("NODE_PATH", "inherited-node-path")
+    binary = Path.expand("../fixtures/tailwindcss-echoes-node-path", __DIR__)
+
+    opts = [
+      canonical_tailwind: [
+        binary: binary,
+        cd: File.cwd!(),
+        env: %{"NODE_PATH" => nil}
+      ]
+    ]
+
+    assert Canonicalizer.canonicalize("p-0 flex", opts) == "unset"
+    assert System.get_env("NODE_PATH") == "inherited-node-path"
+  end
+
   test "reuses one CLI for an env change that resolves to the same config" do
     assert Canonicalizer.canonicalize("p-0 flex", []) == "flex p-0"
     [worker] = running_workers()

test/canonical_tailwind/config_test.exs

@@ -93,6 +93,39 @@ defmodule CanonicalTailwind.ConfigTest do
     cd: File.cwd!()
   ]
 
+  describe ":env" do
+    test "is empty when neither the profile nor the formatter opts set it" do
+      config = resolve_with_env([test_profile: @profile_config], profile: :test_profile)
+
+      assert config.env == %{}
+    end
+
+    test "is taken from the profile" do
+      assert env_from_profile(%{"NODE_PATH" => "deps"}) == %{"NODE_PATH" => "deps"}
+    end
+
+    test "accepts a keyword list as well as a map" do
+      assert env_from_profile([{"NODE_PATH", "deps"}]) == %{"NODE_PATH" => "deps"}
+    end
+
+    test "joins a list value with the path separator" do
+      assert env_from_profile(%{"NODE_PATH" => ["deps", "_build/test"]}) ==
+               %{"NODE_PATH" => "deps:_build/test"}
+    end
+
+    test "set in the formatter opts, overrides the profile's" do
+      profile = Keyword.put(@profile_config, :env, %{"NODE_PATH" => "deps"})
+
+      config =
+        resolve_with_env([env_profile: profile],
+          profile: :env_profile,
+          env: %{"NODE_PATH" => "elsewhere"}
+        )
+
+      assert config.env == %{"NODE_PATH" => "elsewhere"}
+    end
+  end
+
   describe ":input" do
     test "when not specified, no --css is passed to the binary" do
       config = resolve_with_env([bare_profile: [args: []]], profile: :bare_profile)
@@ -203,4 +236,10 @@ defmodule CanonicalTailwind.ConfigTest do
   defp resolve_with_env(tailwind_env, opts \\ []) do
     Config.resolve!([canonical_tailwind: opts], tailwind_env)
   end
+
+  defp env_from_profile(env) do
+    profile = Keyword.put(@profile_config, :env, env)
+
+    resolve_with_env([env_profile: profile], profile: :env_profile).env
+  end
 end

test/fixtures/tailwindcss-echoes-node-path

@@ -0,0 +1,10 @@
+#!/bin/bash
+# Simulates a tailwindcss CLI that replies with the NODE_PATH it was given.
+case "$1" in
+  --help) echo "tailwindcss help (no version)"; exit 0 ;;
+esac
+
+while read -r _line; do
+  echo "${NODE_PATH-unset}"
+done
+exit 0