No color

README.md

@@ -378,7 +378,7 @@ long = true
 # How many lines of Rust are in this code base?
 # e.g. `erd --config rs`
 [rs]
-disk-usage = "word"
+disk-usage = "line"
 level = 1
 pattern = "\\.rs$"
 ```
@@ -773,6 +773,8 @@ If, however, the default behavior doesn't suit your needs you have control over
       - force: Turn on colorization always
 ```
 
+`erdtree` also supports [NO_COLOR](https://no-color.org/).
+
 <p align="center">
   <img src="https://github.com/solidiquis/erdtree/blob/master/assets/colorization.png?raw=true" alt="failed to load picture" />
 </p>

example/.erdtree.toml

@@ -21,6 +21,6 @@ long = true
 
 # How many lines of Rust are in this code base?
 [rs]
-disk-usage = "word"
+disk-usage = "line"
 level = 1
 pattern = "\\.rs$"

src/context/color.rs

@@ -1,4 +1,14 @@
 use clap::ValueEnum;
+use once_cell::sync::OnceCell;
+use std::{env, ffi::OsString};
+
+pub static NO_COLOR: OnceCell<Option<OsString>> = OnceCell::new();
+
+/// Reads in the `NO_COLOR` environment variable to determine whether or not to display color in
+/// the output.
+pub fn no_color_env() {
+    let _ = NO_COLOR.set(env::var_os("NO_COLOR"));
+}
 
 /// Enum to determine how the output should be colorized.
 #[derive(Clone, Copy, Debug, ValueEnum, PartialEq, Eq, Default)]

src/context/mod.rs

@@ -326,7 +326,11 @@ impl Context {
     /// the Coloring, and whether or not stdout is connected to a tty.
     ///
     /// If Coloring is Force then this will always evaluate to `false`.
-    pub const fn no_color(&self) -> bool {
+    pub fn no_color(&self) -> bool {
+        if let Some(Some(var)) = color::NO_COLOR.get() {
+            return !var.is_empty();
+        }
+
         match self.color {
             Coloring::Auto if !self.stdout_is_tty => true,
             Coloring::None => true,

src/main.rs

@@ -79,6 +79,7 @@ fn run() -> Result<(), Box<dyn Error>> {
         return Ok(());
     }
 
+    context::color::no_color_env();
     styles::init(ctx.no_color());
 
     let indicator = (ctx.stdout_is_tty && !ctx.no_progress).then(progress::Indicator::measure);