feat: Add an Elm module (#879)

Former-commit-id: d42137309da457a438b554601f0734db963a193e

9 files changed, 157 insertions, 0 deletions

diff --git a/README.md b/README.md
index 563539b97..bd14f3f71 100644
--- a/README.md
+++ b/README.md
@@ -88,6 +88,7 @@ The prompt shows information you need while you're working, while staying sleek
 ## 🍬 Features
 
 - Prompt character turns red if the last command exits with non-zero code
+- Current Elm version (`🌳`)
 - Current Go version (`🐹`)
 - Current Haskell version (`λ`)
 - Current Java version(`☕`)
diff --git a/docs/config/README.md b/docs/config/README.md
index 2f26cc384..68c37e870 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -102,6 +102,7 @@ prompt_order = [
     "hg_branch",
     "package",
     "dotnet",
+    "elm",
     "golang",
     "haskell",
     "java",
@@ -405,6 +406,34 @@ style = "green"
 heuristic = false
 ```
 
+## Elm
+
+The `elm` module shows the currently installed version of Elm version.
+The module will be shown if any of the following conditions are met:
+
+- The current directory contains a `elm.json` file
+- The current directory contains a `elm-package.json` file
+- The current directory contains a `elm-stuff` folder
+- The current directory contains a `*.elm` files
+
+### Options
+
+| Variable   | Default       | Description                                               |
+| ---------- | ------------- | --------------------------------------------------------- |
+| `symbol`   | `"🌳 "`       | The symbol used before displaying the version of Elm. |
+| `style`    | `"bold cyan"` | The style for the module.                                 |
+| `disabled` | `false`       | Disables the `elm` module.                                |
+
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[elm]
+symbol = "λx.x "
+```
+
 ## Environment Variable
 
 The `env_var` module displays the current value of a selected environment variable.
diff --git a/src/configs/elm.rs b/src/configs/elm.rs
new file mode 100644
index 000000000..5c8e9a968
--- /dev/null
+++ b/src/configs/elm.rs
@@ -0,0 +1,23 @@
+use crate::config::{ModuleConfig, RootModuleConfig, SegmentConfig};
+
+use ansi_term::{Color, Style};
+use starship_module_config_derive::ModuleConfig;
+
+#[derive(Clone, ModuleConfig)]
+pub struct ElmConfig<'a> {
+    pub symbol: SegmentConfig<'a>,
+    pub version: SegmentConfig<'a>,
+    pub style: Style,
+    pub disabled: bool,
+}
+
+impl<'a> RootModuleConfig<'a> for ElmConfig<'a> {
+    fn new() -> Self {
+        ElmConfig {
+            symbol: SegmentConfig::new("🌳 "),
+            version: SegmentConfig::default(),
+            style: Color::Cyan.bold(),
+            disabled: false,
+        }
+    }
+}
diff --git a/src/configs/mod.rs b/src/configs/mod.rs
index b3950b50a..d3c6d4f37 100644
--- a/src/configs/mod.rs
+++ b/src/configs/mod.rs
@@ -6,6 +6,7 @@ pub mod conda;
 pub mod crystal;
 pub mod directory;
 pub mod dotnet;
+pub mod elm;
 pub mod env_var;
 pub mod git_branch;
 pub mod git_commit;
diff --git a/src/configs/starship_root.rs b/src/configs/starship_root.rs
index 14f171792..db024df71 100644
--- a/src/configs/starship_root.rs
+++ b/src/configs/starship_root.rs
@@ -30,6 +30,7 @@ impl<'a> RootModuleConfig<'a> for StarshipRootConfig<'a> {
                 // ↓ Toolchain version modules ↓
                 // (Let's keep these sorted alphabetically)
                 "dotnet",
+                "elm",
                 "golang",
                 "haskell",
                 "java",
diff --git a/src/module.rs b/src/module.rs
index c3d283d88..60108d478 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -17,6 +17,7 @@ pub const ALL_MODULES: &[&str] = &[
     "conda",
     "directory",
     "dotnet",
+    "elm",
     "env_var",
     "git_branch",
     "git_commit",
diff --git a/src/modules/elm.rs b/src/modules/elm.rs
new file mode 100644
index 000000000..2acc87ac5
--- /dev/null
+++ b/src/modules/elm.rs
@@ -0,0 +1,95 @@
+use super::{Context, Module, RootModuleConfig, SegmentConfig};
+
+use crate::configs::elm::ElmConfig;
+use crate::utils;
+
+/// Creates a module with the current Elm version
+///
+/// Will display the Elm version if any of the following criteria are met:
+///     - The current directory contains a `elm.json` file
+///     - The current directory contains a `elm-package.json` file
+///     - The current directory contains a `elm-stuff` folder
+///     - The current directory contains a `*.elm` files
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let is_elm_project = context
+        .try_begin_scan()?
+        .set_files(&["elm.json", "elm-package.json"])
+        .set_extensions(&["elm"])
+        .set_folders(&["elm-stuff"])
+        .is_match();
+
+    if !is_elm_project {
+        return None;
+    }
+
+    let elm_version = utils::exec_cmd("elm", &["--version"])?.stdout;
+    let formatted_version = Some(format!("v{}", elm_version.trim()))?;
+
+    let mut module = context.new_module("elm");
+    let config: ElmConfig = ElmConfig::try_load(module.config);
+    module.set_style(config.style);
+
+    module.create_segment("symbol", &config.symbol);
+    module.create_segment("version", &SegmentConfig::new(&formatted_version));
+
+    Some(module)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::modules::utils::test::render_module;
+    use ansi_term::Color;
+    use std::fs::{self, File};
+    use std::io;
+    use tempfile;
+
+    #[test]
+    fn folder_without_elm() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        let actual = render_module("elm", dir.path());
+        let expected = None;
+        assert_eq!(expected, actual);
+        Ok(())
+    }
+
+    #[test]
+    fn folder_with_elm_json() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("elm.json"))?.sync_all()?;
+        let actual = render_module("elm", dir.path());
+        let expected = Some(format!("via {} ", Color::Cyan.bold().paint("🌳 v0.19.1")));
+        assert_eq!(expected, actual);
+        Ok(())
+    }
+
+    #[test]
+    fn folder_with_elm_package_json() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("elm-package.json"))?.sync_all()?;
+        let actual = render_module("elm", dir.path());
+        let expected = Some(format!("via {} ", Color::Cyan.bold().paint("🌳 v0.19.1")));
+        assert_eq!(expected, actual);
+        Ok(())
+    }
+
+    #[test]
+    fn folder_with_elm_stuff_directory() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        let elmstuff = dir.path().join("elm-stuff");
+        fs::create_dir_all(&elmstuff)?;
+        let actual = render_module("elm", dir.path());
+        let expected = Some(format!("via {} ", Color::Cyan.bold().paint("🌳 v0.19.1")));
+        assert_eq!(expected, actual);
+        Ok(())
+    }
+
+    #[test]
+    fn folder_with_elm_file() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("main.elm"))?.sync_all()?;
+        let actual = render_module("elm", dir.path());
+        let expected = Some(format!("via {} ", Color::Cyan.bold().paint("🌳 v0.19.1")));
+        assert_eq!(expected, actual);
+        Ok(())
+    }
+}
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index 2852d169b..a1a5d192f 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -6,6 +6,7 @@ mod conda;
 mod crystal;
 mod directory;
 mod dotnet;
+mod elm;
 mod env_var;
 mod git_branch;
 mod git_commit;
@@ -51,6 +52,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
         "conda" => conda::module(context),
         "directory" => directory::module(context),
         "dotnet" => dotnet::module(context),
+        "elm" => elm::module(context),
         "env_var" => env_var::module(context),
         "git_branch" => git_branch::module(context),
         "git_commit" => git_commit::module(context),
diff --git a/src/utils.rs b/src/utils.rs
index 01039093d..d9bd29636 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -37,6 +37,10 @@ pub fn exec_cmd(cmd: &str, args: &[&str]) -> Option<CommandOutput> {
         _ => format!("{} {}", cmd, args.join(" ")),
     };
     match command.as_str() {
+        "elm --version" => Some(CommandOutput {
+            stdout: String::from("0.19.1"),
+            stderr: String::default(),
+        }),
         "node --version" => Some(CommandOutput {
             stdout: String::from("v12.0.0"),
             stderr: String::default(),