feat: rebase Vladimir's pr

src/alejandra/src/builder.rs

@@ -1,4 +1,5 @@
 use crate::config::Config;
+use crate::config::Indentation;
 
 #[derive(PartialEq)]
 pub(crate) enum Step {
@@ -15,14 +16,13 @@ pub(crate) enum Step {
 
 #[derive(Clone)]
 pub(crate) struct BuildCtx {
-    pub _config:            Config,
+    pub config:             Config,
     pub force_wide:         bool,
     pub force_wide_success: bool,
     pub indentation:        usize,
     pub pos_old:            crate::position::Position,
     pub path:               String,
     pub vertical:           bool,
-    pub indent:             String,
 }
 
 pub(crate) fn build(
@@ -100,7 +100,12 @@ fn build_step(
                 add_token(
                     builder,
                     rnix::SyntaxKind::TOKEN_WHITESPACE,
-                    &build_ctx.indent.repeat(build_ctx.indentation),
+                    &match build_ctx.config.indentation {
+                        Indentation::FourSpaces => "    ",
+                        Indentation::Tabs => "\t",
+                        Indentation::TwoSpaces => "  ",
+                    }
+                    .repeat(build_ctx.indentation),
                 );
             }
         }

src/alejandra/src/config.rs

@@ -2,4 +2,19 @@ use serde::Deserialize;
 
 /// Configuration used by the formatter
 #[derive(Clone, Copy, Default, Deserialize)]
-pub struct Config {}
+pub struct Config {
+    /// Indentation to use
+    pub indentation: Indentation,
+}
+
+#[derive(Clone, Copy, Default, Deserialize)]
+/// Indentation options
+pub enum Indentation {
+    /// Four spaces
+    FourSpaces,
+    /// Tabs
+    Tabs,
+    #[default]
+    /// Two spaces
+    TwoSpaces,
+}

src/alejandra/src/format.rs

@@ -32,14 +32,13 @@ pub fn in_memory(
     }
 
     let mut build_ctx = crate::builder::BuildCtx {
-        _config: config,
+        config,
         force_wide: false,
         force_wide_success: true,
         indentation: 0,
         path,
         pos_old: crate::position::Position::default(),
         vertical: true,
-        indent,
     };
 
     let after = crate::builder::build(&mut build_ctx, ast.node().into())

src/alejandra/tests/fmt.rs

@@ -1,32 +1,40 @@
 use std::collections::HashMap;
-use std::collections::HashSet;
 use std::io::Write;
 
 use alejandra::config::Config;
+use alejandra::config::Indentation;
 use pretty_assertions::assert_eq;
 
 #[test]
 fn cases() {
     let should_update = std::env::var("UPDATE").is_ok();
 
-    let cases: HashSet<String> = std::fs::read_dir("tests/cases")
-        .unwrap()
-        .map(|entry| entry.unwrap().file_name().into_string().unwrap())
-        .collect();
+    let configs = HashMap::from([
+        ("default", Config::default()),
+        ("indentation-tabs", Config {
+            indentation: Indentation::Tabs,
+            ..Default::default()
+        }),
+    ]);
 
-    let configs = HashMap::from([("", Config::default())]);
+    for (config_name, config) in configs {
+        let cases: Vec<String> =
+            std::fs::read_dir(format!("tests/cases/{}", config_name))
+                .unwrap()
+                .map(|entry| entry.unwrap().file_name().into_string().unwrap())
+                .collect();
 
-    for case in cases {
-        let path_in = format!("tests/cases/{}/in.nix", case);
-        let content_in = std::fs::read_to_string(path_in.clone()).unwrap();
+        for case in cases {
+            let path_in =
+                format!("tests/cases/{}/{}/in.nix", config_name, case);
+            let content_in = std::fs::read_to_string(&path_in).unwrap();
 
-        for (config_name, config) in &configs {
             let path_out =
-                format!("tests/cases/{}/out{}.nix", case, config_name);
+                format!("tests/cases/{}/{}/out.nix", config_name, case);
             let content_got = alejandra::format::in_memory(
                 path_in.clone(),
                 content_in.clone(),
-                config.clone(),
+                config,
             )
             .1;
 
@@ -42,8 +50,9 @@ fn cases() {
 
             assert_eq!(
                 content_out, content_got,
-                "Test case `{case}` failed; see \
-                 `src/alejandra/tests/cases/{case}/`"
+                "Test case `{}/{}` failed; see \
+                 `src/alejandra/tests/cases/{}/{}/`",
+                config_name, case, config_name, case,
             );
         }
     }