feat(ocaml): add `switch_indicator` and `switch_name` variable (#2503)

* feat(ocaml): add switch variable

* feat(ocaml): configurable opam switch display

* docs(ocaml): document opam switch display options

Add `global_switch_indicator` and `local_switch_indicator` config
options.

* style(opam): add `OpamSwitch` type alias

* fix(opam): gracefully handle empty opam switch

Co-authored-by: cdaringe <cdaringe@gmail.com>

4 files changed, 202 insertions, 27 deletions

diff --git a/docs/config/README.md b/docs/config/README.md
index f7b8bef42..bb40af9fa 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -1865,23 +1865,27 @@ By default the module will be shown if any of the following conditions are met:
 
 ### Options
 
-| Option              | Default                              | Description                                             |
-| ------------------- | ------------------------------------ | ------------------------------------------------------- |
-| `format`            | `"via [$symbol($version )]($style)"` | The format string for the module.                       |
-| `symbol`            | `"🐫 "`                              | The symbol used before displaying the version of OCaml. |
-| `detect_extensions` | `["opam", "ml", "mli", "re", "rei"]` | Which extensions should trigger this module.            |
-| `detect_files`      | `["dune", "dune-project", "jbuild", "jbuild-ignore", ".merlin"]` | Which filenames should trigger this module. |
-| `detect_folders`    | `["_opam", "esy.lock"]`              | Which folders should trigger this module.               |
-| `style`             | `"bold yellow"`                      | The style for the module.                               |
-| `disabled`          | `false`                              | Disables the `ocaml` module.                            |
+| Option                    | Default                                                                  | Description                                             |
+| ------------------------- | ------------------------------------------------------------------------ | ------------------------------------------------------- |
+| `format`                  | `"via [$symbol($version )(\($switch_indicator$switch_name\) )]($style)"` | The format string for the module.                       |
+| `symbol`                  | `"🐫 "`                                                                  | The symbol used before displaying the version of OCaml. |
+| `global_switch_indicator` | `""`                                                                     | The format string used to represent global OPAM switch. |
+| `local_switch_indicator`  | `"*"`                                                                    | The format string used to represent local OPAM switch.  |
+| `detect_extensions`       | `["opam", "ml", "mli", "re", "rei"]`                                     | Which extensions should trigger this module.            |
+| `detect_files`            | `["dune", "dune-project", "jbuild", "jbuild-ignore", ".merlin"]`         | Which filenames should trigger this module.             |
+| `detect_folders`          | `["_opam", "esy.lock"]`                                                  | Which folders should trigger this module.               |
+| `style`                   | `"bold yellow"`                                                          | The style for the module.                               |
+| `disabled`                | `false`                                                                  | Disables the `ocaml` module.                            |
 
 ### Variables
 
-| Variable | Example   | Description                          |
-| -------- | --------- | ------------------------------------ |
-| version  | `v4.10.0` | The version of `ocaml`               |
-| symbol   |           | Mirrors the value of option `symbol` |
-| style\*  |           | Mirrors the value of option `style`  |
+| Variable         | Example      | Description                                                       |
+| ---------------- | ------------ | ----------------------------------------------------------------- |
+| version          | `v4.10.0`    | The version of `ocaml`                                            |
+| switch_name      | `my-project` | The active OPAM switch                                            |
+| switch_indicator |              | Mirrors the value of `indicator` for currently active OPAM switch |
+| symbol           |              | Mirrors the value of option `symbol`                              |
+| style\*          |              | Mirrors the value of option `style`                               |
 
 \*: This variable can only be used as a part of a style string
 
diff --git a/src/configs/ocaml.rs b/src/configs/ocaml.rs
index 8b1d51fe2..fe149837f 100644
--- a/src/configs/ocaml.rs
+++ b/src/configs/ocaml.rs
@@ -5,6 +5,8 @@ use starship_module_config_derive::ModuleConfig;
 
 #[derive(Clone, ModuleConfig, Serialize)]
 pub struct OCamlConfig<'a> {
+    pub global_switch_indicator: &'a str,
+    pub local_switch_indicator: &'a str,
     pub format: &'a str,
     pub symbol: &'a str,
     pub style: &'a str,
@@ -17,7 +19,9 @@ pub struct OCamlConfig<'a> {
 impl<'a> Default for OCamlConfig<'a> {
     fn default() -> Self {
         OCamlConfig {
-            format: "via [$symbol($version )]($style)",
+            global_switch_indicator: "",
+            local_switch_indicator: "*",
+            format: "via [$symbol($version )(\\($switch_indicator$switch_name\\) )]($style)",
             symbol: "🐫 ",
             style: "bold yellow",
             disabled: false,
diff --git a/src/modules/ocaml.rs b/src/modules/ocaml.rs
index 0b7a19dd1..634f1bd7f 100644
--- a/src/modules/ocaml.rs
+++ b/src/modules/ocaml.rs
@@ -1,8 +1,18 @@
 use super::{Context, Module, RootModuleConfig};
+use once_cell::sync::Lazy;
+use std::ops::Deref;
+use std::path::Path;
 
 use crate::configs::ocaml::OCamlConfig;
 use crate::formatter::StringFormatter;
 
+#[derive(Debug, PartialEq)]
+enum SwitchType {
+    Global,
+    Local,
+}
+type OpamSwitch = (SwitchType, String);
+
 /// Creates a module with the current OCaml version
 pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
     let mut module = context.new_module("ocaml");
@@ -18,10 +28,19 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
         return None;
     }
 
+    let opam_switch: Lazy<Option<OpamSwitch>, _> = Lazy::new(|| get_opam_switch(context));
+
     let parsed = StringFormatter::new(config.format).and_then(|formatter| {
         formatter
             .map_meta(|variable, _| match variable {
                 "symbol" => Some(config.symbol),
+                "switch_indicator" => {
+                    let (switch_type, _) = &opam_switch.deref().as_ref()?;
+                    match switch_type {
+                        SwitchType::Global => Some(config.global_switch_indicator),
+                        SwitchType::Local => Some(config.local_switch_indicator),
+                    }
+                }
                 _ => None,
             })
             .map_style(|variable| match variable {
@@ -29,6 +48,10 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
                 _ => None,
             })
             .map(|variable| match variable {
+                "switch_name" => {
+                    let (_, name) = opam_switch.deref().as_ref()?;
+                    Some(Ok(name.to_string()))
+                }
                 "version" => {
                     let is_esy_project = context
                         .try_begin_scan()?
@@ -58,14 +81,50 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
     Some(module)
 }
 
+fn get_opam_switch(context: &Context) -> Option<OpamSwitch> {
+    let opam_switch = context
+        .exec_cmd("opam", &["switch", "show", "--safe"])?
+        .stdout;
+
+    parse_opam_switch(&opam_switch.trim())
+}
+
+fn parse_opam_switch(opam_switch: &str) -> Option<OpamSwitch> {
+    if opam_switch.is_empty() {
+        return None;
+    }
+
+    let path = Path::new(opam_switch);
+    if !path.has_root() {
+        Some((SwitchType::Global, opam_switch.to_string()))
+    } else {
+        Some((SwitchType::Local, path.file_name()?.to_str()?.to_string()))
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::test::ModuleRenderer;
+    use super::{parse_opam_switch, SwitchType};
+    use crate::{test::ModuleRenderer, utils::CommandOutput};
     use ansi_term::Color;
     use std::fs::{self, File};
     use std::io;
 
     #[test]
+    fn test_parse_opam_switch() {
+        let global_switch = "ocaml-base-compiler.4.10.0";
+        let local_switch = "/path/to/my-project";
+        assert_eq!(
+            parse_opam_switch(global_switch),
+            Some((SwitchType::Global, "ocaml-base-compiler.4.10.0".to_string()))
+        );
+        assert_eq!(
+            parse_opam_switch(local_switch),
+            Some((SwitchType::Local, "my-project".to_string()))
+        );
+    }
+
+    #[test]
     fn folder_without_ocaml_file() -> io::Result<()> {
         let dir = tempfile::tempdir()?;
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
@@ -80,7 +139,10 @@ mod tests {
         File::create(dir.path().join("any.opam"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -91,7 +153,10 @@ mod tests {
         fs::create_dir_all(dir.path().join("_opam"))?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -106,7 +171,10 @@ mod tests {
             "{\"dependencies\": {\"ocaml\": \"4.8.1000\"}}",
         )?;
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.08.1 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.08.1 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -117,7 +185,10 @@ mod tests {
         File::create(dir.path().join("dune"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -128,7 +199,10 @@ mod tests {
         File::create(dir.path().join("dune-project"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -139,7 +213,10 @@ mod tests {
         File::create(dir.path().join("jbuild"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -150,7 +227,10 @@ mod tests {
         File::create(dir.path().join("jbuild-ignore"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -161,7 +241,10 @@ mod tests {
         File::create(dir.path().join(".merlin"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -172,7 +255,10 @@ mod tests {
         File::create(dir.path().join("any.ml"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -183,7 +269,10 @@ mod tests {
         File::create(dir.path().join("any.mli"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -194,7 +283,10 @@ mod tests {
         File::create(dir.path().join("any.re"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
-        let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
         assert_eq!(expected, actual);
         dir.close()
     }
@@ -205,8 +297,79 @@ mod tests {
         File::create(dir.path().join("any.rei"))?.sync_all()?;
 
         let actual = ModuleRenderer::new("ocaml").path(dir.path()).collect();
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (default) ")
+        ));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn without_opam_switch() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("any.ml"))?.sync_all()?;
+
+        let actual = ModuleRenderer::new("ocaml")
+            .cmd(
+                "opam switch show --safe",
+                Some(CommandOutput {
+                    stdout: String::default(),
+                    stderr: String::default(),
+                }),
+            )
+            .path(dir.path())
+            .collect();
         let expected = Some(format!("via {}", Color::Yellow.bold().paint("🐫 v4.10.0 ")));
         assert_eq!(expected, actual);
         dir.close()
     }
+
+    #[test]
+    fn with_global_opam_switch() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("any.ml"))?.sync_all()?;
+
+        let actual = ModuleRenderer::new("ocaml")
+            .cmd(
+                "opam switch show --safe",
+                Some(CommandOutput {
+                    stdout: String::from("ocaml-base-compiler.4.10.0\n"),
+                    stderr: String::default(),
+                }),
+            )
+            .path(dir.path())
+            .collect();
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow
+                .bold()
+                .paint("🐫 v4.10.0 (ocaml-base-compiler.4.10.0) ")
+        ));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn with_local_opam_switch() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("any.ml"))?.sync_all()?;
+
+        let actual = ModuleRenderer::new("ocaml")
+            .cmd(
+                "opam switch show --safe",
+                Some(CommandOutput {
+                    stdout: String::from("/path/to/my-project\n"),
+                    stderr: String::default(),
+                }),
+            )
+            .path(dir.path())
+            .collect();
+        let expected = Some(format!(
+            "via {}",
+            Color::Yellow.bold().paint("🐫 v4.10.0 (*my-project) ")
+        ));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
 }
diff --git a/src/utils.rs b/src/utils.rs
index 3c02ece94..381a628fd 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -129,6 +129,10 @@ active boot switches: -d:release\n",
             stdout: String::from("4.10.0\n"),
             stderr: String::default(),
         }),
+        "opam switch show --safe" => Some(CommandOutput {
+            stdout: String::from("default\n"),
+            stderr: String::default(),
+        }),
         "esy ocaml -vnum" => Some(CommandOutput {
             stdout: String::from("4.08.1\n"),
             stderr: String::default(),