feat: allow configuration to be read from stdin

src/main.rs

@@ -1,3 +1,5 @@
+use std::io::Read;
+
 use clap::Parser;
 
 use i3status_rs::config::Config;
@@ -6,6 +8,8 @@ use i3status_rs::escape::Escaped;
 use i3status_rs::widget::{State, Widget};
 use i3status_rs::{protocol, util, BarState};
 
+const STDIN_FILE_DESIGNATOR: &str = "-";
+
 fn main() {
     env_logger::init();
 
@@ -22,9 +26,39 @@ fn main() {
         .build()
         .unwrap()
         .block_on(async move {
-            let config_path = util::find_file(&args.config, None, Some("toml"))
-                .or_error(|| format!("Configuration file '{}' not found", args.config))?;
-            let mut config: Config = util::deserialize_toml_file(&config_path)?;
+            let mut config: Config = match args.config.as_str() {
+                STDIN_FILE_DESIGNATOR => {
+                    // read from stdin
+                    let mut config_str = String::new();
+
+                    let size = std::io::stdin()
+                        .read_to_string(&mut config_str)
+                        .or_error(|| {
+                            "Configuration file could not be read from stdin".to_string()
+                        })?;
+
+                    if size == 0 {
+                        return Err(i3status_rs::errors::Error {
+                            kind: ErrorKind::Config,
+                            message: None,
+                            cause: None,
+                            block: None,
+                        });
+                    }
+
+                    util::deserialize_toml(&config_str, None)?
+                }
+                _ => {
+                    // read from file path
+                    let config_path = util::find_file(&args.config, None, Some("toml"))
+                        .or_error(|| format!("Configuration file '{}' not found", args.config))?;
+                    let config_str = util::read_file(&config_path)
+                        .await
+                        .or_error(|| format!("Configuration file '{}' not found", args.config))?;
+                    util::deserialize_toml(&config_str, Some(&config_path))?
+                }
+            };
+
             let blocks = std::mem::take(&mut config.blocks);
             let mut bar = BarState::new(config);
             for block_config in blocks {

src/util.rs

@@ -95,7 +95,19 @@ where
     let contents = std::fs::read_to_string(path)
         .or_error(|| format!("Failed to read file: {}", path.display()))?;
 
-    toml::from_str(&contents).map_err(|err| {
+    self::deserialize_toml(&contents, Some(path))
+}
+
+pub fn deserialize_toml<T>(contents: &String, file_path: Option<&Path>) -> Result<T>
+where
+    T: DeserializeOwned,
+{
+    let source = match file_path {
+        Some(msg) => msg.display().to_string(),
+        _ => String::from("(from stdin)"),
+    };
+
+    toml::from_str(contents).map_err(|err| {
         #[allow(deprecated)]
         let location_msg = err
             .span()
@@ -109,7 +121,7 @@ where
             .unwrap_or_default();
         Error::new(format!(
             "Failed to deserialize TOML file {}{}: {}",
-            path.display(),
+            source,
             location_msg,
             err.message()
         ))