doc: improve README

- add table of contents
- new troubleshooting section on docker/tty
- add "commands" synopsis
- clarify language in a few sections

Author: flavorjones

README.md

@@ -2,6 +2,32 @@
 
 [Tailwind CSS](https://tailwindcss.com) is a utility-first CSS framework packed with classes like flex, pt-4, text-center and rotate-90 that can be composed to build any design, directly in your markup.
 
+<!-- regenerate TOC with `rake format:toc` -->
+
+<!-- toc -->
+
+- [Installation](#installation)
+  * [Using a local installation of `tailwindcss`](#using-a-local-installation-of-tailwindcss)
+- [Developing with Tailwindcss](#developing-with-tailwindcss)
+  * [Configuration and commands](#configuration-and-commands)
+  * [Building for production](#building-for-production)
+  * [Building for testing](#building-for-testing)
+  * [Building unminified assets](#building-unminified-assets)
+  * [Live rebuild](#live-rebuild)
+  * [Using with PostCSS](#using-with-postcss)
+  * [Custom inputs or outputs](#custom-inputs-or-outputs)
+- [Troubleshooting](#troubleshooting)
+  * [Running in a docker container exits prematurely](#running-in-a-docker-container-exits-prematurely)
+  * [Conflict with sassc-rails](#conflict-with-sassc-rails)
+  * [Class names must be spelled out](#class-names-must-be-spelled-out)
+  * [ERROR: Cannot find the tailwindcss executable for &lt;supported platform&gt;](#error-cannot-find-the-tailwindcss-executable-for-ltsupported-platformgt)
+  * ["No such file or directory" running on Alpine (musl)](#no-such-file-or-directory-running-on-alpine-musl)
+  * [Using asset-pipeline assets](#using-asset-pipeline-assets)
+  * [Conflict with pre-existing asset pipeline stylesheets](#conflict-with-pre-existing-asset-pipeline-stylesheets)
+- [License](#license)
+
+<!-- tocstop -->
+
 ## Installation
 
 With Rails 7 you can generate a new application preconfigured with Tailwind by using `--css tailwind`. If you're adding Tailwind later, you need to:
@@ -24,27 +50,56 @@ Supported platforms are:
 
 ### Using a local installation of `tailwindcss`
 
-If you are not able to use the vendored standalone executables (for example, if you're on an unsupported platform), you can use a local installation of the `tailwindcss` executable by setting an environment variable named `TAILWINDCSS_INSTALL_DIR` to the directory containing the executable.
+If you are not able to use the vendored standalone executables (for example, if you're on an unsupported platform), you can use a local installation of the `tailwindcss` executable by setting an environment variable named `TAILWINDCSS_INSTALL_DIR` to the directory path containing the executable.
 
-For example, if you've installed `tailwindcss` so that the executable is found at `/node_modules/bin/tailwindcss`, then you should set your environment variable like so:
+For example, if you've installed `tailwindcss` so that the executable is found at `/path/to/node_modules/bin/tailwindcss`, then you should set your environment variable like so:
 
 ``` sh
 TAILWINDCSS_INSTALL_DIR=/path/to/node_modules/bin
 ```
 
-This also works with relative paths. If you've installed into your app's directory at `./node_modules/.bin/tailwindcss`:
+or, for relative paths like `./node_modules/.bin/tailwindcss`:
 
 ``` sh
 TAILWINDCSS_INSTALL_DIR=node_modules/.bin
 ```
 
+
 ## Developing with Tailwindcss
 
-### Configuration
+### Configuration and commands
+
+#### Configuration file: `config/tailwind.config.js`
 
 You can customize the Tailwind build through the `config/tailwind.config.js` file, just like you would if Tailwind was running in a traditional node installation. All the first-party plugins are supported.
 
-The installer will create your Tailwind input file in `app/assets/stylesheets/application.tailwind.css`. This is where you import the plugins you want to use, and where you can setup your custom `@apply` rules. When you run `rails tailwindcss:build`, this input file will be used to generate the output in `app/assets/builds/tailwind.css`. That's the output CSS that you'll include in your app (the installer automatically configures this, alongside the Inter font as well).
+#### Input file: `app/assets/stylesheets/application.tailwind.css`
+
+The installer will generate a Tailwind input file in `app/assets/stylesheets/application.tailwind.css`. This is where you import the plugins you want to use, and where you can setup your custom `@apply` rules.
+
+#### Output file: `app/assets/builds/tailwind.css`
+
+When you run `rails tailwindcss:build`, the input file will be used to generate the output in `app/assets/builds/tailwind.css`. That's the output CSS that you'll include in your app (the installer automatically configures this, alongside the Inter font as well).
+
+#### Commands
+
+This gem makes several Rails tasks available, some of which have multiple options which can be combined.
+
+Synopsis:
+
+- `bin/rails tailwindcss:install` - installs the configuration file, output file, and `Procfile.dev`
+- `bin/rails tailwindcss:build` - generate the output file
+  - `bin/rails tailwindcss:build[debug]` - generate unminimized output
+- `bin/rails tailwindcss:watch` - start live rebuilds, generating output on file changes
+  - `bin/rails tailwindcss:watch[debug]` - generate unminimized output
+  - `bin/rails tailwindcss:watch[poll]` - for systems without file system events
+  - `bin/rails tailwindcss:watch[always]` - for systems without TTY (e.g., some docker containers)
+
+Note that you can combine task options, e.g. `rails tailwindcss:watch[debug,poll]`.
+
+This gem also makes available a Puma plugin to manage a live rebuild process when you run `rails server` (see "Live Rebuild" section below).
+
+This gem also generates a `Procfile.dev` file which will run both the rails server and a live rebuild process (see "Live Rebuild" section below).
 
 
 ### Building for production
@@ -57,17 +112,23 @@ The `tailwindcss:build` is automatically attached to `assets:precompile`, so bef
 The `tailwindcss:build` task is automatically attached to the `test:prepare` Rake task. This task runs before test commands. If you run `bin/rails test` in your CI environment, your Tailwind output will be generated before tests run.
 
 
-### Update assets automatically
+### Building unminified assets
+
+If you want unminified assets, you can pass a `debug` argument to the rake task, i.e. `rails tailwindcss:build[debug]` or `rails tailwindcss:watch[debug]`.
+
+
+### Live rebuild
 
 While you're developing your application, you want to run Tailwind in "watch" mode, so changes are automatically reflected in the generated CSS output. You can do this in a few different ways:
 
-- use the [Puma](https://puma.io/) plugin to integrate "watch" with `rails server`, or
-- run `rails tailwindcss:watch` as a separate process, or
-- run `bin/dev` which uses [Foreman](https://github.com/ddollar/foreman)
+- use this gem's [Puma](https://puma.io/) plugin to integrate "watch" with `rails server`,
+- or run `rails tailwindcss:watch` as a separate process,
+- or run `bin/dev` which uses [Foreman](https://github.com/ddollar/foreman)
+
 
 #### Puma plugin
 
-The Puma plugin requires you to add this line to your `puma.rb` configuration:
+This gem ships with a Puma plugin. To use it, add this line to your `puma.rb` configuration:
 
 ```ruby
 plugin :tailwindcss if ENV.fetch("RAILS_ENV", "development") == "development"
@@ -80,7 +141,13 @@ and then running `rails server` will run the Tailwind watch process in the backg
 
 This is a flexible command, which can be run with a few different options.
 
-If you are running `rails tailwindcss:watch` on a system that doesn't fully support file system events, pass a `poll` argument to the task to instruct tailwindcss to instead use polling: `rails tailwindcss:watch[poll]`. If you use `bin/dev` then you should modify your `Procfile.dev`.
+If you are running `rails tailwindcss:watch` on a system that doesn't fully support file system events, pass a `poll` argument to the task to instruct tailwindcss to instead use polling:
+
+```
+rails tailwindcss:watch[poll]
+```
+
+(If you use `bin/dev` then you should modify your `Procfile.dev` to use the `poll` option.)
 
 If you are running `rails tailwindcss:watch` as a process in a Docker container, set `tty: true` in `docker-compose.yml` for the appropriate container to keep the watch process running.
 
@@ -92,13 +159,6 @@ If you are running `rails tailwindcss:watch` in a docker container without a tty
 Running `bin/dev` invokes Foreman to start both the Tailwind watch process and the rails server in development mode based on your `Procfile.dev` file.
 
 
-### Debugging with unminified assets
-
-If you want unminified assets, you can pass a `debug` argument to the rake task, i.e. `rails tailwindcss:build[debug]` or `rails tailwindcss:watch[debug]`.
-
-Note that you can combine task options, e.g. `rails tailwindcss:watch[debug,poll]`.
-
-
 ### Using with PostCSS
 
 If you want to use PostCSS as a preprocessor, create a custom `config/postcss.config.js` and it will be loaded automatically.
@@ -126,6 +186,12 @@ If you need to use a custom input or output file, you can run `bundle exec tailw
 
 Some common problems experienced by users ...
 
+### Running in a docker container exits prematurely
+
+If you are running `rails tailwindcss:watch` as a process in a Docker container, set `tty: true` in `docker-compose.yml` for the appropriate container to keep the watch process running.
+
+If you are running `rails tailwindcss:watch` in a docker container without a tty, pass the `always` argument to the task to instruct tailwindcss to keep the watcher alive even when `stdin` is closed: `rails tailwindcss:watch[always]`. If you use `bin/dev` then you should modify your `Procfile.dev`.
+
 ### Conflict with sassc-rails
 
 Tailwind uses modern CSS features that are not recognized by the `sassc-rails` extension that was included by default in the Gemfile for Rails 6. In order to avoid any errors like `SassC::SyntaxError`, you must remove that gem from your Gemfile.
@@ -215,6 +281,7 @@ If you get a warning `Unrecognized at-rule or error parsing at-rule ‘@tailwind
 
 To fix the warning, you can either remove the `application.css`, if you don't plan to use the asset pipeline for stylesheets, and instead rely on TailwindCSS completely for styles. This is what this installer assumes. Else, if you do want to keep using the asset pipeline in parallel, make sure to remove the `require_tree .` line from the `application.css`.
 
+
 ## License
 
 Tailwind for Rails is released under the [MIT License](https://opensource.org/licenses/MIT).

Rakefile

@@ -12,3 +12,15 @@ Rake::TestTask.new(:test) do |t|
 end
 
 task default: :test
+
+namespace "format" do
+  desc "Regenerate table of contents in README"
+  task "toc" do
+    require "mkmf"
+    if find_executable0("markdown-toc")
+      sh "markdown-toc --maxdepth=3 -i README.md"
+    else
+      puts "WARN: cannot find markdown-toc, skipping. install with 'npm install markdown-toc'"
+    end
+  end
+end