feat(module): Add a meson devenv indicator (#4389)

* feat(module): Add a meson devenv indicator

Adds a Meson Developer Environment indicator, if the MESON_DEVENV
variable is set. Inside a `meson devenv`, the prompt will include the
current Meson project name

This also contains a new Truncate utility function, which may be adapted for other modules in the future

* docs: Add Meson to presets

8 files changed, 247 insertions, 0 deletions

diff --git a/src/configs/meson.rs b/src/configs/meson.rs
new file mode 100644
index 000000000..0325c3f56
--- /dev/null
+++ b/src/configs/meson.rs
@@ -0,0 +1,30 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Clone, Deserialize, Serialize)]
+#[cfg_attr(
+    feature = "config-schema",
+    derive(schemars::JsonSchema),
+    schemars(deny_unknown_fields)
+)]
+#[serde(default)]
+pub struct MesonConfig<'a> {
+    pub truncation_length: u32,
+    pub truncation_symbol: &'a str,
+    pub format: &'a str,
+    pub symbol: &'a str,
+    pub style: &'a str,
+    pub disabled: bool,
+}
+
+impl<'a> Default for MesonConfig<'a> {
+    fn default() -> Self {
+        MesonConfig {
+            truncation_length: std::u32::MAX,
+            truncation_symbol: "…",
+            format: "via [$symbol$project]($style) ",
+            symbol: "⬢ ",
+            style: "blue bold",
+            disabled: false,
+        }
+    }
+}
diff --git a/src/configs/mod.rs b/src/configs/mod.rs
index ec47d5012..e767d0d81 100644
--- a/src/configs/mod.rs
+++ b/src/configs/mod.rs
@@ -46,6 +46,7 @@ pub mod line_break;
 pub mod localip;
 pub mod lua;
 pub mod memory_usage;
+pub mod meson;
 pub mod nim;
 pub mod nix_shell;
 pub mod nodejs;
@@ -184,6 +185,8 @@ pub struct FullConfig<'a> {
     #[serde(borrow)]
     memory_usage: memory_usage::MemoryConfig<'a>,
     #[serde(borrow)]
+    meson: meson::MesonConfig<'a>,
+    #[serde(borrow)]
     nim: nim::NimConfig<'a>,
     #[serde(borrow)]
     nix_shell: nix_shell::NixShellConfig<'a>,
diff --git a/src/configs/starship_root.rs b/src/configs/starship_root.rs
index aeb03358a..6cc4da77b 100644
--- a/src/configs/starship_root.rs
+++ b/src/configs/starship_root.rs
@@ -87,6 +87,7 @@ pub const PROMPT_ORDER: &[&str] = &[
     "buf",
     "nix_shell",
     "conda",
+    "meson",
     "spack",
     "memory_usage",
     "aws",
diff --git a/src/module.rs b/src/module.rs
index c83947e24..c23e9435d 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -54,6 +54,7 @@ pub const ALL_MODULES: &[&str] = &[
     "localip",
     "lua",
     "memory_usage",
+    "meson",
     "nim",
     "nix_shell",
     "nodejs",
diff --git a/src/modules/meson.rs b/src/modules/meson.rs
new file mode 100644
index 000000000..afbedcb5a
--- /dev/null
+++ b/src/modules/meson.rs
@@ -0,0 +1,98 @@
+use super::{Context, Module, ModuleConfig};
+
+use super::utils::truncate::truncate_text;
+use crate::configs::meson::MesonConfig;
+use crate::formatter::StringFormatter;
+
+/// Creates a module with the current Meson dev environment
+///
+/// Will display the Meson environment if `$MESON_DEVENV` and `MESON_PROJECT_NAME` are set.
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let meson_env = context.get_env("MESON_DEVENV")?;
+    let project_env = context.get_env("MESON_PROJECT_NAME")?;
+    if meson_env != "1" || project_env.trim().is_empty() {
+        return None;
+    }
+
+    let mut module = context.new_module("meson");
+    let config: MesonConfig = MesonConfig::try_load(module.config);
+
+    let truncated_text = truncate_text(
+        &project_env,
+        config.truncation_length as usize,
+        config.truncation_symbol,
+    );
+
+    let parsed = StringFormatter::new(config.format).and_then(|formatter| {
+        formatter
+            .map_meta(|variable, _| match variable {
+                "symbol" => Some(config.symbol),
+                _ => None,
+            })
+            .map_style(|variable| match variable {
+                "style" => Some(Ok(config.style)),
+                _ => None,
+            })
+            .map(|variable| match variable {
+                "project" => Some(Ok(&truncated_text)),
+                _ => None,
+            })
+            .parse(None, Some(context))
+    });
+
+    module.set_segments(match parsed {
+        Ok(segments) => segments,
+        Err(error) => {
+            log::warn!("Error in module `meson`:\n{}", error);
+            return None;
+        }
+    });
+
+    Some(module)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test::ModuleRenderer;
+    use nu_ansi_term::Color;
+
+    #[test]
+    fn not_in_env() {
+        let actual = ModuleRenderer::new("meson").collect();
+
+        let expected = None;
+
+        assert_eq!(expected, actual);
+    }
+
+    #[test]
+    fn env_set() {
+        let actual = ModuleRenderer::new("meson")
+            .env("MESON_DEVENV", "1")
+            .env("MESON_PROJECT_NAME", "starship")
+            .collect();
+
+        let expected = Some(format!("via {} ", Color::Blue.bold().paint("⬢ starship")));
+
+        assert_eq!(expected, actual);
+    }
+
+    #[test]
+    fn env_invalid_devenv() {
+        let actual = ModuleRenderer::new("meson")
+            .env("MESON_DEVENV", "0")
+            .env("MESON_PROJECT_NAME", "starship")
+            .collect();
+        let expected = None;
+        assert_eq!(expected, actual);
+    }
+    #[test]
+    fn env_invalid_project_name() {
+        let actual = ModuleRenderer::new("meson")
+            .env("MESON_DEVENV", "1")
+            .env("MESON_PROJECT_NAME", " ")
+            .collect();
+        let expected = None;
+        assert_eq!(expected, actual);
+    }
+}
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index b6575281b..6626e1c77 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -43,6 +43,7 @@ mod line_break;
 mod localip;
 mod lua;
 mod memory_usage;
+mod meson;
 mod nim;
 mod nix_shell;
 mod nodejs;
@@ -137,6 +138,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
             "localip" => localip::module(context),
             "lua" => lua::module(context),
             "memory_usage" => memory_usage::module(context),
+            "meson" => meson::module(context),
             "nim" => nim::module(context),
             "nix_shell" => nix_shell::module(context),
             "nodejs" => nodejs::module(context),
@@ -242,6 +244,9 @@ pub fn description(module: &str) -> &'static str {
         "localip" => "The currently assigned ipv4 address",
         "lua" => "The currently installed version of Lua",
         "memory_usage" => "Current system memory and swap usage",
+        "meson" => {
+            "The current Meson environment, if $MESON_DEVENV and $MESON_PROJECT_NAME are set"
+        }
         "nim" => "The currently installed version of Nim",
         "nix_shell" => "The nix-shell environment",
         "nodejs" => "The currently installed version of NodeJS",
diff --git a/src/modules/utils/mod.rs b/src/modules/utils/mod.rs
index 1d509c14b..209da8ed6 100644
--- a/src/modules/utils/mod.rs
+++ b/src/modules/utils/mod.rs
@@ -7,3 +7,5 @@ pub mod directory_win;
 pub mod directory_nix;
 
 pub mod path;
+
+pub mod truncate;
diff --git a/src/modules/utils/truncate.rs b/src/modules/utils/truncate.rs
new file mode 100644
index 000000000..9ec920cb6
--- /dev/null
+++ b/src/modules/utils/truncate.rs
@@ -0,0 +1,107 @@
+use unicode_segmentation::UnicodeSegmentation;
+
+/// Truncate a string to only have a set number of characters
+///
+/// Will truncate a string to only show the last `length` character in the string.
+/// If a length of `0` is provided, the string will not be truncated and the original
+/// will be returned.
+pub fn truncate_text(text: &str, length: usize, truncation_symbol: &str) -> String {
+    if length == 0 {
+        return String::from(text);
+    }
+
+    let truncated_graphemes = get_graphemes(text, length);
+    // The truncation symbol should only be added if we truncated
+    let truncated_and_symbol = if length < graphemes_len(text) {
+        let truncation_symbol = get_graphemes(truncation_symbol, 1);
+        truncated_graphemes + truncation_symbol.as_str()
+    } else {
+        truncated_graphemes
+    };
+
+    truncated_and_symbol
+}
+
+fn get_graphemes(text: &str, length: usize) -> String {
+    UnicodeSegmentation::graphemes(text, true)
+        .take(length)
+        .collect::<Vec<&str>>()
+        .concat()
+}
+
+fn graphemes_len(text: &str) -> usize {
+    UnicodeSegmentation::graphemes(text, true).count()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_multi_char_truncation_symbol() {
+        let actual = truncate_text("1337_hello_world", 15, "apple");
+
+        assert_eq!("1337_hello_worla", actual);
+    }
+
+    #[test]
+    fn test_changed_truncation_symbol() {
+        test_truncate_length("1337_hello_world", 15, "1337_hello_worl", "%")
+    }
+
+    #[test]
+    fn test_no_truncation_symbol() {
+        test_truncate_length("1337_hello_world", 15, "1337_hello_worl", "")
+    }
+
+    #[test]
+    fn test_ascii_boundary_below() {
+        test_truncate_length("1337_hello_world", 15, "1337_hello_worl", "…")
+    }
+
+    #[test]
+    fn test_ascii_boundary_on() {
+        test_truncate_length("1337_hello_world", 16, "1337_hello_world", "")
+    }
+
+    #[test]
+    fn test_ascii_boundary_above() {
+        test_truncate_length("1337_hello_world", 17, "1337_hello_world", "")
+    }
+
+    #[test]
+    fn test_one() {
+        test_truncate_length("1337_hello_world", 1, "1", "…")
+    }
+
+    #[test]
+    fn test_negative() {
+        test_truncate_length("1337_hello_world", -1, "1337_hello_world", "")
+    }
+
+    #[test]
+    fn test_hindi_truncation() {
+        test_truncate_length("नमस्ते", 3, "नमस्", "…")
+    }
+
+    #[test]
+    fn test_hindi_truncation2() {
+        test_truncate_length("नमस्त", 3, "नमस्", "…")
+    }
+
+    #[test]
+    fn test_japanese_truncation() {
+        test_truncate_length("がんばってね", 4, "がんばっ", "…")
+    }
+
+    fn test_truncate_length(
+        text: &str,
+        truncate_length: i64,
+        expected: &str,
+        truncation_symbol: &str,
+    ) {
+        let actual = truncate_text(text, truncate_length as usize, truncation_symbol);
+
+        assert_eq!(format!("{}{}", expected, truncation_symbol), actual);
+    }
+}