feat(scala): Add scala module (#2409)

* Add support for scala ( w/o sbt )

* Add scala description

* Change scala color to bold red

* update scala extensions in README

* failed lint

* cr changes ( regex, simplify parsing, imports )

* Scala readme punctuation

Co-authored-by: David Knaack <davidkna@users.noreply.github.com>

Co-authored-by: David Knaack <davidkna@users.noreply.github.com>

9 files changed, 255 insertions, 0 deletions

diff --git a/docs/config/README.md b/docs/config/README.md
index 926e26dc0..af580016a 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -216,6 +216,7 @@ $purescript\
 $python\
 $ruby\
 $rust\
+$scala\
 $swift\
 $terraform\
 $vagrant\
@@ -2272,6 +2273,49 @@ The module will be shown if any of the following conditions are met:
 format = "via [⚙️ $version](red bold)"
 ```
 
+
+## Scala
+
+The `scala` module shows the currently installed version of Scala.
+By default the module will be shown if any of the following conditions are met:
+
+- The current directory contains a `build.sbt`, `.scalaenv` or `.sbtenv` file
+- The current directory contains a file with the `.scala` or `.sbt` extension
+- The current directory contains a directory named `.metals`
+
+### Options
+
+
+| Option              | Default                                    | Description                                      |
+| ------------------- | -------------------------------------------| -----------------------------------------------  |
+| `format`            | `"via [${symbol}(${version} )]($style)"`   | The format for the module.                       |
+| `detect_extensions` | `["sbt", "scala"]`                         | Which extensions should trigger this module.     |
+| `detect_files`      | `[".scalaenv", ".sbtenv", "build.sbt"]`    | Which filenames should trigger this module.      |
+| `detect_folders`    | `[".metals"]`                              | Which folders should trigger this modules.       |
+| `symbol`            | `"🆂 "`                                    | A format string representing the symbol of Scala.   |
+| `style`             | `"red dimmed"`                             | The style for the module.                        |
+| `disabled`          | `false`                                    | Disables the `scala` module.                     |
+
+### Variables
+
+| Variable | Example    | Description                          |
+| -------- | -----------| ------------------------------------ |
+| version  | `2.13.5`   | The version of `scala`               |
+| 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
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[scala]
+symbol = "🌟 "
+```
+
+
 ## Shell
 
 The `shell` module shows an indicator for currently used shell.
diff --git a/docs/presets/README.md b/docs/presets/README.md
index f8939242c..040cc207b 100644
--- a/docs/presets/README.md
+++ b/docs/presets/README.md
@@ -86,6 +86,9 @@ symbol = " "
 [rust]
 symbol = " "
 
+[scala]
+symbol = " "
+
 [swift]
 symbol = "ﯣ "
 ```
diff --git a/src/configs/mod.rs b/src/configs/mod.rs
index 1052a6736..4ad15699c 100644
--- a/src/configs/mod.rs
+++ b/src/configs/mod.rs
@@ -42,6 +42,7 @@ pub mod purescript;
 pub mod python;
 pub mod ruby;
 pub mod rust;
+pub mod scala;
 pub mod shell;
 pub mod shlvl;
 pub mod singularity;
diff --git a/src/configs/scala.rs b/src/configs/scala.rs
new file mode 100644
index 000000000..3c5fc670e
--- /dev/null
+++ b/src/configs/scala.rs
@@ -0,0 +1,28 @@
+use crate::config::{ModuleConfig, RootModuleConfig};
+
+use starship_module_config_derive::ModuleConfig;
+
+#[derive(Clone, ModuleConfig)]
+pub struct ScalaConfig<'a> {
+    pub disabled: bool,
+    pub format: &'a str,
+    pub style: &'a str,
+    pub symbol: &'a str,
+    pub detect_extensions: Vec<&'a str>,
+    pub detect_files: Vec<&'a str>,
+    pub detect_folders: Vec<&'a str>,
+}
+
+impl<'a> RootModuleConfig<'a> for ScalaConfig<'a> {
+    fn new() -> Self {
+        ScalaConfig {
+            format: "via [$symbol($version )]($style)",
+            disabled: false,
+            style: "red bold",
+            symbol: "🆂 ",
+            detect_extensions: vec!["sbt", "scala"],
+            detect_files: vec![".scalaenv", ".sbtenv", "build.sbt"],
+            detect_folders: vec![".metals"],
+        }
+    }
+}
diff --git a/src/configs/starship_root.rs b/src/configs/starship_root.rs
index a73f0229a..9064e5afe 100644
--- a/src/configs/starship_root.rs
+++ b/src/configs/starship_root.rs
@@ -50,6 +50,7 @@ pub const PROMPT_ORDER: &[&str] = &[
     "python",
     "ruby",
     "rust",
+    "scala",
     "swift",
     "terraform",
     "vagrant",
diff --git a/src/module.rs b/src/module.rs
index 7a6961beb..c5ca928e7 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -34,6 +34,7 @@ pub const ALL_MODULES: &[&str] = &[
     "hg_branch",
     "hostname",
     "java",
+    "scala",
     "jobs",
     "julia",
     "kotlin",
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index 207d4e66b..35dd4f37c 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -43,6 +43,7 @@ mod purescript;
 mod python;
 mod ruby;
 mod rust;
+mod scala;
 mod shell;
 mod shlvl;
 mod singularity;
@@ -114,6 +115,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
             "python" => python::module(context),
             "ruby" => ruby::module(context),
             "rust" => rust::module(context),
+            "scala" => scala::module(context),
             "shell" => shell::module(context),
             "shlvl" => shlvl::module(context),
             "singularity" => singularity::module(context),
@@ -192,6 +194,7 @@ pub fn description(module: &str) -> &'static str {
         "python" => "The currently installed version of Python",
         "ruby" => "The currently installed version of Ruby",
         "rust" => "The currently installed version of Rust",
+        "scala" => "The currently installed version of Scala",
         "swift" => "The currently installed version of Swift",
         "shell" => "The currently used shell indicator",
         "shlvl" => "The current value of SHLVL",
diff --git a/src/modules/scala.rs b/src/modules/scala.rs
new file mode 100644
index 000000000..f02f44cc6
--- /dev/null
+++ b/src/modules/scala.rs
@@ -0,0 +1,170 @@
+use crate::configs::scala::ScalaConfig;
+use crate::formatter::StringFormatter;
+
+use super::{Context, Module, RootModuleConfig};
+
+use regex::Regex;
+
+const SCALA_VERSION_PATTERN: &str = "version[\\s](?P<version>[^\\s]+)";
+
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let mut module = context.new_module("scala");
+    let config: ScalaConfig = ScalaConfig::try_load(module.config);
+
+    let is_scala_project = context
+        .try_begin_scan()?
+        .set_files(&config.detect_files)
+        .set_extensions(&config.detect_extensions)
+        .set_folders(&config.detect_folders)
+        .is_match();
+
+    if !is_scala_project {
+        return None;
+    }
+
+    let parsed = StringFormatter::new(config.format).and_then(|formatter| {
+        formatter
+            .map_meta(|var, _| match var {
+                "symbol" => Some(config.symbol),
+                _ => None,
+            })
+            .map_style(|variable| match variable {
+                "style" => Some(Ok(config.style)),
+                _ => None,
+            })
+            .map(|variable| match variable {
+                "version" => {
+                    let scala_version = get_scala_version(context)?;
+                    Some(Ok(scala_version))
+                }
+                _ => None,
+            })
+            .parse(None)
+    });
+
+    module.set_segments(match parsed {
+        Ok(segments) => segments,
+        Err(error) => {
+            log::warn!("Error in module `scala`:\n{}", error);
+            return None;
+        }
+    });
+
+    Some(module)
+}
+
+fn get_scala_version(context: &Context) -> Option<String> {
+    let output = context.exec_cmd("scalac", &["-version"])?;
+    let scala_version = if output.stdout.is_empty() {
+        output.stderr
+    } else {
+        output.stdout
+    };
+
+    parse_scala_version(&scala_version)
+}
+
+fn parse_scala_version(scala_version: &str) -> Option<String> {
+    let re = Regex::new(SCALA_VERSION_PATTERN).ok()?;
+    let captures = re.captures(scala_version)?;
+    let version = &captures["version"];
+
+    Some(format!("v{}", &version))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::test::ModuleRenderer;
+    use ansi_term::Color;
+    use std::fs::{self, File};
+    use std::io;
+
+    #[test]
+    fn test_parse_scala_version() {
+        let scala_2_13 =
+            "Scala compiler version 2.13.5 -- Copyright 2002-2020, LAMP/EPFL and Lightbend, Inc.";
+        assert_eq!(parse_scala_version(scala_2_13), Some("v2.13.5".to_string()));
+    }
+
+    #[test]
+    fn test_parse_dotty_version() {
+        let dotty_version = "Scala compiler version 3.0.0-RC1 -- Copyright 2002-2021, LAMP/EPFL";
+        assert_eq!(
+            parse_scala_version(dotty_version),
+            Some("v3.0.0-RC1".to_string())
+        );
+    }
+
+    #[test]
+    fn folder_without_scala_file() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        let actual = ModuleRenderer::new("scala").path(dir.path()).collect();
+        let expected = None;
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_scala_file() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("Test.scala"))?.sync_all()?;
+        let actual = ModuleRenderer::new("scala").path(dir.path()).collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("🆂 v2.13.5 ")));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_scala_file_no_scala_installed() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("Test.scala"))?.sync_all()?;
+        let actual = ModuleRenderer::new("scala")
+            .cmd("scalac -version", None)
+            .path(dir.path())
+            .collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("🆂 ")));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_sbt_file() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("build.sbt"))?.sync_all()?;
+        let actual = ModuleRenderer::new("scala").path(dir.path()).collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("🆂 v2.13.5 ")));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_scala_env_file() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join(".scalaenv"))?.sync_all()?;
+        let actual = ModuleRenderer::new("scala").path(dir.path()).collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("🆂 v2.13.5 ")));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_sbt_env_file() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join(".sbtenv"))?.sync_all()?;
+        let actual = ModuleRenderer::new("scala").path(dir.path()).collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("🆂 v2.13.5 ")));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_metals_dir() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        fs::create_dir_all(dir.path().join(".metals"))?;
+        let actual = ModuleRenderer::new("scala").path(dir.path()).collect();
+        let expected = Some(format!("via {}", Color::Red.bold().paint("🆂 v2.13.5 ")));
+        assert_eq!(expected, actual);
+        dir.close()
+    }
+}
diff --git a/src/utils.rs b/src/utils.rs
index 352efb84f..3c02ece94 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -86,6 +86,10 @@ Elixir 1.10 (compiled with Erlang/OTP 22)\n",
             stdout: String::from("OpenJDK 64-Bit Server VM (13.0.2+8) for bsd-amd64 JRE (13.0.2+8), built on Feb  6 2020 02:07:52 by \"brew\" with clang 4.2.1 Compatible Apple LLVM 11.0.0 (clang-1100.0.33.17)"),
             stderr: String::default(),
         }),
+        "scalac -version" => Some(CommandOutput {
+            stdout: String::from("Scala compiler version 2.13.5 -- Copyright 2002-2020, LAMP/EPFL and Lightbend, Inc."),
+            stderr: String::default(),
+        }),
         "julia --version" => Some(CommandOutput {
             stdout: String::from("julia version 1.4.0\n"),
             stderr: String::default(),