feat: $gemset variable for Ruby module (#5429)

* $gemset variable for Ruby module

* typo

* Added test for no GEM_HOME env set

* Formatting

* Uses `rvm current` for gemset, no more version num

2 files changed, 74 insertions, 5 deletions

diff --git a/docs/config/README.md b/docs/config/README.md
index 213439514..0719540fd 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -3772,11 +3772,12 @@ Starship gets the current Ruby version by running `ruby -v`.
 
 ### Variables
 
-| Variable | Example  | Description                          |
-| -------- | -------- | ------------------------------------ |
-| version  | `v2.5.1` | The version of `ruby`                |
-| symbol   |          | Mirrors the value of option `symbol` |
-| style\*  |          | Mirrors the value of option `style`  |
+| Variable | Example  | Description                                 |
+| -------- | -------- | ------------------------------------------- |
+| version  | `v2.5.1` | The version of `ruby`                       |
+| symbol   |          | Mirrors the value of option `symbol`        |
+| style\*  |          | Mirrors the value of option `style`         |
+| gemset   | `test`   | Optional, gets the current RVM gemset name. |
 
 *: This variable can only be used as a part of a style string
 
diff --git a/src/modules/ruby.rs b/src/modules/ruby.rs
index 498fefc3f..da056246d 100644
--- a/src/modules/ruby.rs
+++ b/src/modules/ruby.rs
@@ -1,3 +1,5 @@
+use regex::Regex;
+
 use super::{Context, Module, ModuleConfig};
 
 use crate::configs::ruby::RubyConfig;
@@ -45,6 +47,9 @@ pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
                     config.version_format,
                 )
                 .map(Ok),
+                "gemset" => {
+                    format_rvm_gemset(&context.exec_cmd("rvm", &["current"])?.stdout).map(Ok)
+                }
                 _ => None,
             })
             .parse(None, Some(context))
@@ -81,10 +86,21 @@ fn format_ruby_version(ruby_version: &str, version_format: &str) -> Option<Strin
     }
 }
 
+fn format_rvm_gemset(current: &str) -> Option<String> {
+    let gemset_re = Regex::new(r"@(\S+)").unwrap();
+    if let Some(gemset) = gemset_re.captures(current) {
+        let gemset_name = gemset.get(1)?.as_str();
+        return Some(gemset_name.to_string());
+    }
+
+    None
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
     use crate::test::ModuleRenderer;
+    use crate::utils::CommandOutput;
     use nu_ansi_term::Color;
     use std::fs::File;
     use std::io;
@@ -164,6 +180,58 @@ mod tests {
     }
 
     #[test]
+    fn rvm_gemset_active() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("any.rb"))?.sync_all()?;
+
+        let actual = ModuleRenderer::new("ruby")
+            .path(dir.path())
+            .cmd(
+                "rvm current",
+                Some(CommandOutput {
+                    stdout: String::from("ruby-2.5.1@test\n"),
+                    stderr: String::default(),
+                }),
+            )
+            .config(toml::toml! {
+                [ruby]
+                format = "via [$symbol($version)@($gemset )]($style)"
+                version_format = "${raw}"
+            })
+            .collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("💎 2.5.1@test ")));
+
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn rvm_gemset_not_active() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("any.rb"))?.sync_all()?;
+
+        let actual = ModuleRenderer::new("ruby")
+            .path(dir.path())
+            .cmd(
+                "rvm current",
+                Some(CommandOutput {
+                    // with no gemset, `rvm current` outputs an empty string
+                    stdout: String::default(),
+                    stderr: String::default(),
+                }),
+            )
+            .config(toml::toml! {
+                [ruby]
+                format = "via [$symbol($version)(@$gemset) ]($style)"
+            })
+            .collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("💎 v2.5.1 ")));
+
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
     fn test_format_ruby_version() {
         let config = RubyConfig::default();
         assert_eq!(