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 766732fe69
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:56:02 2020 +0800

    fix: Add test for StyleVariableHolder

commit 444334ad20
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 9796a66a96
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:51:26 2020 +0800

    test: Add tests for VariableHolder

commit 479d4a72fa
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 22:41:47 2020 +0800

    feat: Add trait StyleVariableHolder

commit 21d40c6f4e
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 e7dd987fd7
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Sat Apr 25 15:10:12 2020 +0800

    misc: Minor changes on docs and codes

commit 71020b0397
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Fri Apr 24 20:51:45 2020 +0800

    feat(format_string): Add syntax for positional segments

commit 3b459f4379
Author: heyrict <xiezh0831@yahoo.co.jp>
Date:   Wed Apr 22 17:49:15 2020 +0800

    fix: Fix clippy

commit 2fb052d68c
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>

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/).