feat(r-lang): add module for R programming language (#1475)

* feat(formatter): Allow scoped variables (#1094)

* feat: Allow scoped variables

, with the following improvements to the format string parser.

- Add documentation to spec
- Simplify some syntax in the spec
- Rewrite for loop with iterators

* Added support for R programming language.

* Removed unnecessary debug log used during dev process.

* Make the `R` command upper case as the *nix OS executables are case sensitives and the correct command is upper-case.

* Changed comments to reflect R features (rather than node.js where code was coming from).

* feat(format_string): Allow positional segments (#1138)

* feat(format_string): Allow using variables in a style string (#1130)

* fix(format_string): Allow multiple variable mappers (#1142)

* refactor: Add error handling to variables (#1148)

* Squashed commit of changes with meta variables:

commit 5beb3bca18f0b0c822b740afb3778ccb1e3a7d19
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Mon Apr 27 09:52:59 2020 +0800

    fix: Cache variables in meta variables properly

commit 49b9324942dd55350c87107d0e8c7d1592d92e8a
Merge: cc575bc 260a1ab
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sun Apr 26 21:34:52 2020 +0800

    Merge branch 'feat/format-string' into meta-variables

commit cc575bc27cbf87c4197e96d2fa5416d4932e45d7
Merge: 3ed2d32 e0c1901
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sun Apr 26 12:16:12 2020 +0800

    Merge branch 'feat/format-string' into meta-variables

commit 3ed2d326c9f625930bdd72cea736c1d0eab6d381
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sun Apr 26 11:06:28 2020 +0800

    refactor(format_string): Allow returning error in variable mapper

commit 766732fe697df947538fe12ca92a8eb8e7bfea3e
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:56:02 2020 +0800

    fix: Add test for StyleVariableHolder

commit 444334ad206a68132fa6257b83c3992b7b790981
Merge: 479d4a7 9796a66
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:52:27 2020 +0800

    Merge branch 'positional-segments' into style-variables

commit 9796a66a9679597676e7fd859197fd542e8042dc
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:51:26 2020 +0800

    test: Add tests for VariableHolder

commit 479d4a72fa58fd8aa777acd8228d4834407a7b6a
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:41:47 2020 +0800

    feat: Add trait StyleVariableHolder

commit 21d40c6f4e2d12b34fdec4e2e38b6ad0f91217a3
Merge: 3b459f4 e7dd987
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:17:11 2020 +0800

    Merge branch 'positional-segments' into style-variables

commit e7dd987fd7b01a82c6012ba7055d1dd9b5fd84aa
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 15:10:12 2020 +0800

    misc: Minor changes on docs and codes

commit 71020b0397a86e850ad5beda926aa9416250025c
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Fri Apr 24 20:51:45 2020 +0800

    feat(format_string): Add syntax for positional segments

commit 3b459f4379b08defce50c57a903502513ad1b2b6
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Wed Apr 22 17:49:15 2020 +0800

    fix: Fix clippy

commit 2fb052d68cb46680c081f5a0e25e2c3fbdc9e204
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Wed Apr 22 17:02:09 2020 +0800

    feat: Add map_style method to feed values in style string

* fix: Change error type of StringFormatter::new

* fix: Fix rustfmt

* tests: Add tests to variable errors

* docs: Add documentation

* chore: Rename positional to conditional (#1166)

* docs: Add docs for format strings (#1083)


Co-authored-by: Thomas O'Donnell <andytom@users.noreply.github.com>

* refactor(rust): Use format strings (#1063)

* Updated to latest string formatter's changes.

* feat(format-string): add format string support to battery module (#1158)

* update battery module with format string

* update battery module docs

* update battery module with format string

* update battery module docs

* fix battery module with new StringFormatter api

* fix clippy warnings

* Update docs/config/README.md

Co-authored-by: Zhenhui Xie <xiezh0831@yahoo.co.jp>

* battery symbols now supports format-string

* battery symbols now support format-string
remove space between symbol and percentage
fix battery config

Co-authored-by: Zhenhui Xie <xiezh0831@yahoo.co.jp>

* refactor(golang): Use format strings (#1066)

* refactor(golang): Use format strings

* docs(golang): Update docs

* docs(golang): Update docs

* fix: Update to upstream API changes

* docs(golang): Update docs

Co-authored-by: heyrict <xiezh0831@yahoo.co.jp>

* Fixed a few inconsistencies.

* Removed string clone in favor of a reference.

* Update src/modules/r.rs

Reverting the r version string formatting to a more idiomatic way of handling it.

Co-authored-by: Thomas O'Donnell <andytom@users.noreply.github.com>

* Update src/configs/r.rs

Co-authored-by: Zhenhui Xie <xiezh0831@yahoo.co.jp>

* Updated documentation to reflect changes in config.

* refactor(java): Added formatter support for Java module. (#1084)

* refactor(haskell): Added formatter support for the Haskell module. (#1111)

* Added formatter support for the Haskell module.

* Updated haskell module with latest formatter code changes.

* Changed documentation for latest Haskell string formatter changes.

* Fixed a few inconsistencies.

* Removed unnecessary variable cloning for using reference instead.

* refactor(env_var): Added formatter support for the env_var module (#1180)

* refactor(memory_usage): Added formatter support for memory_usage module (#1182)

* Migrated the memory usage module to string formatter' support.

* Fixed a few inconsistencies.

* Removed cloning of variables to instead use references.

* refactor(cmd_duration): Use format strings (#1200)

* Fixed format issue in code.

* Fixed compilation error after adding new 'r' module in root config.

* Added .Rproj extension file to be detected with R prog lang.

* Aligned R module code with existing ones.

* Update src/configs/r.rs

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

* fix: Added rconfig to fullconfig and fixed broken api calls

* Apply suggestions from code review

Co-authored-by: Dario Vladović <d.vladimyr@gmail.com>

* Update src/modules/r.rs

Co-authored-by: Dario Vladović <d.vladimyr@gmail.com>

* Addressed PR comments.

Cleaned up code and fixed code errors.

* Updated docs for consistency purpose.

Co-authored-by: Milo <50248166+Milo123459@users.noreply.github.com>

* refactor: Renamed the `r` module to `rlang`

* test: Provided R fixture and R module renderer test

* doc: Updated rlang mod config to reflect latest detection changes

* fix: Added missing rlang entry in config/mod

* feat: Added version formatted fined grained configuration

* Added version_format in R lang documentation.

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

* review: Addressed later comments

* fix: README was missing a previously present section for Python

* Fix: Test was not updated for previous version string upgrade.

* fix: Upgraded R version in remaining test.

Co-authored-by: Zhenhui Xie <xiezh0831@yahoo.co.jp>
Co-authored-by: Thomas O'Donnell <andytom@users.noreply.github.com>
Co-authored-by: Luca Rinaldi <lucarin@protonmail.com>
Co-authored-by: John Letey <johnletey@gmail.com>
Co-authored-by: Tilmann Meyer <47182955+ATiltedTree@users.noreply.github.com>
Co-authored-by: David Knaack <davidkna@users.noreply.github.com>
Co-authored-by: Dario Vladović <d.vladimyr@gmail.com>
Co-authored-by: Milo <50248166+Milo123459@users.noreply.github.com>

8 files changed, 255 insertions, 0 deletions

diff --git a/docs/config/README.md b/docs/config/README.md
index d6d159cdd..a7db84528 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -2285,6 +2285,49 @@ detect_extensions = []
 python_binary = ["./venv/bin/python", "python", "python3", "python2"]
 ```
 
+## R
+
+The `rlang` module shows the currently installed version of R. The module will be shown if 
+any of the following conditions are met:
+
+- The current directory contains a file with the `.R` extension.
+- The current directory contains a file with the `.Rd` extension.
+- The current directory contains a file with the `.Rmd` extension.
+- The current directory contains a file with the `.Rproj` extension.
+- The current directory contains a file with the `.Rsx` extension.
+- The current directory contains a `.Rprofile` file
+- The current directory contains a `.Rproj.user` folder
+
+### Options
+
+| Option              | Default                              | Description                                   |
+|---------------------|--------------------------------------|-----------------------------------------------|
+| `format`            | `"via [$symbol($version )]($style)"` | The format for the module.                    |
+| `version_format` | `"v${raw}"` | The version format. Available vars are `raw`, `major`, `minor`, & `patch`|
+| `symbol`            | `"📐"`                               | A format string representing the symbol of R. |
+| `style`             | `"blue bold"`                        | The style for the module.                     |
+| `detect_extensions` | `["R", "Rd", "Rmd", "Rproj", "Rsx"]` | Which extensions should trigger this module   |
+| `detect_files`      | `[".Rprofile"]`                      | Which filenames should trigger this module    |
+| `detect_folders`    | `[".Rproj.user"]`                    | Which folders should trigger this module      |
+| `disabled`          | `false`                              | Disables the `r` module.                      |
+
+### Variables
+
+| Variable | Example       | Description                          |
+| -------- | ------------- | ------------------------------------ |
+| version  | `v4.0.5`      | The version of `R`                   |
+| symbol   |               | Mirrors the value of option `symbol` |
+| style    | `"blue bold"` | Mirrors the value of option `style`  |
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[rlang]
+format = "with [📐 $version](blue bold) "
+```
+
 ## Red
 
 By default the `red` module shows the currently installed version of [Red](https://www.red-lang.org/).
diff --git a/src/configs/mod.rs b/src/configs/mod.rs
index e307060da..ec5434fc3 100644
--- a/src/configs/mod.rs
+++ b/src/configs/mod.rs
@@ -47,6 +47,7 @@ pub mod php;
 pub mod purescript;
 pub mod python;
 pub mod red;
+pub mod rlang;
 pub mod ruby;
 pub mod rust;
 pub mod scala;
@@ -117,6 +118,7 @@ pub struct FullConfig<'a> {
     php: php::PhpConfig<'a>,
     purescript: purescript::PureScriptConfig<'a>,
     python: python::PythonConfig<'a>,
+    rlang: rlang::RLangConfig<'a>,
     red: red::RedConfig<'a>,
     ruby: ruby::RubyConfig<'a>,
     rust: rust::RustConfig<'a>,
@@ -186,6 +188,7 @@ impl<'a> Default for FullConfig<'a> {
             purescript: Default::default(),
             python: Default::default(),
             red: Default::default(),
+            rlang: Default::default(),
             ruby: Default::default(),
             rust: Default::default(),
             scala: Default::default(),
diff --git a/src/configs/rlang.rs b/src/configs/rlang.rs
new file mode 100644
index 000000000..e08852829
--- /dev/null
+++ b/src/configs/rlang.rs
@@ -0,0 +1,31 @@
+use crate::config::ModuleConfig;
+
+use serde::Serialize;
+use starship_module_config_derive::ModuleConfig;
+
+#[derive(Clone, ModuleConfig, Serialize)]
+pub struct RLangConfig<'a> {
+    pub format: &'a str,
+    pub version_format: &'a str,
+    pub style: &'a str,
+    pub symbol: &'a str,
+    pub disabled: bool,
+    pub detect_extensions: Vec<&'a str>,
+    pub detect_files: Vec<&'a str>,
+    pub detect_folders: Vec<&'a str>,
+}
+
+impl<'a> Default for RLangConfig<'a> {
+    fn default() -> Self {
+        RLangConfig {
+            format: "via [$symbol($version )]($style)",
+            version_format: "v${raw}",
+            style: "blue bold",
+            symbol: "📐 ",
+            disabled: false,
+            detect_extensions: vec!["R", "Rd", "Rmd", "Rproj", "Rsx"],
+            detect_files: vec![".Rprofile"],
+            detect_folders: vec![".Rproj.user"],
+        }
+    }
+}
diff --git a/src/configs/starship_root.rs b/src/configs/starship_root.rs
index f8cc2c62d..bf656ebea 100644
--- a/src/configs/starship_root.rs
+++ b/src/configs/starship_root.rs
@@ -52,6 +52,7 @@ pub const PROMPT_ORDER: &[&str] = &[
     "php",
     "purescript",
     "python",
+    "rlang",
     "red",
     "ruby",
     "rust",
diff --git a/src/module.rs b/src/module.rs
index 860ca04c9..67b0f5d02 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -52,6 +52,7 @@ pub const ALL_MODULES: &[&str] = &[
     "perl",
     "purescript",
     "python",
+    "rlang",
     "red",
     "ruby",
     "crystal",
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index b255a7f2a..4e06309cf 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -43,6 +43,7 @@ mod php;
 mod purescript;
 mod python;
 mod red;
+mod rlang;
 mod ruby;
 mod rust;
 mod scala;
@@ -118,6 +119,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
             "php" => php::module(context),
             "purescript" => purescript::module(context),
             "python" => python::module(context),
+            "rlang" => rlang::module(context),
             "red" => red::module(context),
             "ruby" => ruby::module(context),
             "rust" => rust::module(context),
@@ -201,6 +203,7 @@ pub fn description(module: &str) -> &'static str {
         "php" => "The currently installed version of PHP",
         "purescript" => "The currently installed version of PureScript",
         "python" => "The currently installed version of Python",
+        "rlang" => "The currently installed version of R",
         "red" => "The currently installed version of Red",
         "ruby" => "The currently installed version of Ruby",
         "rust" => "The currently installed version of Rust",
diff --git a/src/modules/rlang.rs b/src/modules/rlang.rs
new file mode 100644
index 000000000..e6cac083f
--- /dev/null
+++ b/src/modules/rlang.rs
@@ -0,0 +1,159 @@
+use super::{Context, Module, RootModuleConfig};
+use crate::formatter::VersionFormatter;
+
+use crate::configs::rlang::RLangConfig;
+use crate::formatter::StringFormatter;
+
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let mut module = context.new_module("rlang");
+    let config: RLangConfig = RLangConfig::try_load(module.config);
+
+    let is_r_project = context
+        .try_begin_scan()?
+        .set_files(&config.detect_files)
+        .set_extensions(&config.detect_extensions)
+        .set_folders(&config.detect_folders)
+        .is_match();
+    if !is_r_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 r_version = get_r_version(context)?;
+                    VersionFormatter::format_module_version(
+                        module.get_name(),
+                        &r_version,
+                        config.version_format,
+                    )
+                    .map(Ok)
+                }
+                _ => None,
+            })
+            .parse(None)
+    });
+
+    module.set_segments(match parsed {
+        Ok(segments) => segments,
+        Err(error) => {
+            log::warn!("Error in module `rlang`:\n{}", error);
+            return None;
+        }
+    });
+
+    Some(module)
+}
+
+fn get_r_version(context: &Context) -> Option<String> {
+    let r_version = context.exec_cmd("R", &["--version"])?.stderr;
+    parse_version(&r_version)
+}
+
+fn parse_version(r_version: &str) -> Option<String> {
+    r_version
+        .lines()
+        // take first line
+        .next()?
+        // split into ["R", "version", "3.6.3", "(2020-02-29)", ...]
+        .split_whitespace()
+        // and pick version entry at index 2, i.e. "3.6.3".
+        .nth(2)
+        .map(ToString::to_string)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::parse_version;
+    use crate::test::ModuleRenderer;
+    use ansi_term::Color;
+    use std::fs;
+    use std::fs::File;
+    use std::io;
+
+    #[test]
+    fn test_parse_r_version() {
+        let r_v3 = r#"R version 4.1.0 (2021-05-18) -- "Camp Pontanezen"
+Copyright (C) 2021 The R Foundation for Statistical Computing
+Platform: x86_64-w64-mingw32/x64 (64-bit)\n
+
+R is free software and comes with ABSOLUTELY NO WARRANTY.
+You are welcome to redistribute it under the terms of the
+GNU General Public License versions 2 or 3.
+For more information about these matters see
+https://www.gnu.org/licenses/."#;
+        assert_eq!(parse_version(r_v3), Some(String::from("4.1.0")));
+    }
+
+    #[test]
+    fn folder_with_r_files() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("analysis.R"))?.sync_all()?;
+        check_r_render(&dir);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_rd_files() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("analysis.Rd"))?.sync_all()?;
+        check_r_render(&dir);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_rmd_files() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("analysis.Rmd"))?.sync_all()?;
+        check_r_render(&dir);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_rproj_files() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("analysis.Rproj"))?.sync_all()?;
+        check_r_render(&dir);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_rsx_files() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join("analysis.Rsx"))?.sync_all()?;
+        check_r_render(&dir);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_rprofile_files() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        File::create(dir.path().join(".Rprofile"))?.sync_all()?;
+        check_r_render(&dir);
+        dir.close()
+    }
+
+    #[test]
+    fn folder_with_rproj_user_folder() -> io::Result<()> {
+        let dir = tempfile::tempdir()?;
+        let rprofile = dir.path().join(".Rproj.user");
+        fs::create_dir_all(&rprofile)?;
+        check_r_render(&dir);
+        dir.close()
+    }
+
+    fn check_r_render(dir: &tempfile::TempDir) {
+        let actual = ModuleRenderer::new("rlang").path(dir.path()).collect();
+        let expected = Some(format!("via {}", Color::Blue.bold().paint("📐 v4.1.0 ")));
+        assert_eq!(expected, actual);
+    }
+}
diff --git a/src/utils.rs b/src/utils.rs
index 2c32c09a0..67265c9c8 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -175,6 +175,20 @@ active boot switches: -d:release\n",
             stdout: String::from("Python 3.8.0\n"),
             stderr: String::default(),
         }),
+        "R --version" => Some(CommandOutput {
+            stdout: String::default(),
+            stderr: String::from(
+                r#"R version 4.1.0 (2021-05-18) -- "Camp Pontanezen"
+Copyright (C) 2021 The R Foundation for Statistical Computing
+Platform: x86_64-w64-mingw32/x64 (64-bit)\n
+
+R is free software and comes with ABSOLUTELY NO WARRANTY.
+You are welcome to redistribute it under the terms of the
+GNU General Public License versions 2 or 3.
+For more information about these matters see
+https://www.gnu.org/licenses/."#
+            ),
+        }),
         "red --version" => Some(CommandOutput {
             stdout: String::from("0.6.4\n"),
             stderr: String::default()