feat: Auto-detect interactive shell for pretty output

Author: Techassi

rust/boil/src/show/images/cli.rs

@@ -1,4 +1,4 @@
-use clap::Args;
+use clap::{Args, ValueEnum};
 
 use crate::build::image::Image;
 
@@ -8,6 +8,15 @@ pub struct ShowImagesArguments {
     pub image: Vec<Image>,
 
     /// Pretty print the structured output.
-    #[arg(long)]
-    pub pretty: bool,
+    #[arg(long, value_enum, default_value_t = Pretty::default())]
+    pub pretty: Pretty,
+}
+
+// #[derive(Clone, Debug, Default, strum::Display, strum::EnumString)]
+#[derive(Clone, Debug, Default, ValueEnum)]
+pub enum Pretty {
+    #[default]
+    Auto,
+    Always,
+    Never,
 }

rust/boil/src/show/images/mod.rs

@@ -1,11 +1,10 @@
-use std::collections::BTreeMap;
+use std::{collections::BTreeMap, io::IsTerminal};
 
-use serde::{Serialize, ser::SerializeSeq};
 use snafu::{ResultExt, Snafu};
 
 use crate::{
     build::bakefile::{Targets, TargetsError, TargetsOptions},
-    show::images::cli::ShowImagesArguments,
+    show::images::cli::{Pretty, ShowImagesArguments},
 };
 
 pub mod cli;
@@ -66,14 +65,14 @@ pub fn run_command(arguments: ShowImagesArguments) -> Result<(), Error> {
     print_to_stdout(list, arguments.pretty)
 }
 
-fn print_to_stdout(list: BTreeMap<String, Vec<String>>, pretty: bool) -> Result<(), Error> {
+fn print_to_stdout(list: BTreeMap<String, Vec<String>>, pretty: Pretty) -> Result<(), Error> {
     let stdout = std::io::stdout();
 
-    let list = OneOrMany(list);
-
-    if pretty {
-        serde_json::to_writer_pretty(stdout, &list).context(SerializeListSnafu)
-    } else {
-        serde_json::to_writer(stdout, &list).context(SerializeListSnafu)
+    match pretty {
+        Pretty::Always | Pretty::Auto if stdout.is_terminal() => {
+            serde_json::to_writer_pretty(stdout, &list)
+        }
+        _ => serde_json::to_writer(stdout, &list),
     }
+    .context(SerializeListSnafu)
 }