feat: Add the `git_metrics` module (#2827)

This PR adds a new module named git_metrics. It shows the added/deleted lines in the current git repository following the format: "[+$added_lines]($added_style) [-$deleted_lines]($deleted_style)".

7 files changed, 307 insertions, 1 deletions

diff --git a/src/configs/git_metrics.rs b/src/configs/git_metrics.rs
new file mode 100644
index 000000000..f3e52e200
--- /dev/null
+++ b/src/configs/git_metrics.rs
@@ -0,0 +1,23 @@
+use crate::config::ModuleConfig;
+
+use serde::Serialize;
+use starship_module_config_derive::ModuleConfig;
+
+#[derive(Clone, ModuleConfig, Serialize)]
+pub struct GitMetricsConfig<'a> {
+    pub added_style: &'a str,
+    pub deleted_style: &'a str,
+    pub format: &'a str,
+    pub disabled: bool,
+}
+
+impl<'a> Default for GitMetricsConfig<'a> {
+    fn default() -> Self {
+        GitMetricsConfig {
+            added_style: "bold green",
+            deleted_style: "bold red",
+            format: "[+$added]($added_style) [-$deleted]($deleted_style) ",
+            disabled: true,
+        }
+    }
+}
diff --git a/src/configs/mod.rs b/src/configs/mod.rs
index ec5434fc3..658c4553b 100644
--- a/src/configs/mod.rs
+++ b/src/configs/mod.rs
@@ -23,6 +23,7 @@ pub mod erlang;
 pub mod gcloud;
 pub mod git_branch;
 pub mod git_commit;
+pub mod git_metrics;
 pub mod git_state;
 pub mod git_status;
 pub mod go;
@@ -95,6 +96,7 @@ pub struct FullConfig<'a> {
     gcloud: gcloud::GcloudConfig<'a>,
     git_branch: git_branch::GitBranchConfig<'a>,
     git_commit: git_commit::GitCommitConfig<'a>,
+    git_metrics: git_metrics::GitMetricsConfig<'a>,
     git_state: git_state::GitStateConfig<'a>,
     git_status: git_status::GitStatusConfig<'a>,
     golang: go::GoConfig<'a>,
@@ -164,6 +166,7 @@ impl<'a> Default for FullConfig<'a> {
             gcloud: Default::default(),
             git_branch: Default::default(),
             git_commit: Default::default(),
+            git_metrics: Default::default(),
             git_state: Default::default(),
             git_status: Default::default(),
             golang: Default::default(),
diff --git a/src/configs/starship_root.rs b/src/configs/starship_root.rs
index bf656ebea..7d5bfcdab 100644
--- a/src/configs/starship_root.rs
+++ b/src/configs/starship_root.rs
@@ -26,6 +26,7 @@ pub const PROMPT_ORDER: &[&str] = &[
     "git_branch",
     "git_commit",
     "git_state",
+    "git_metrics",
     "git_status",
     "hg_branch",
     "docker_context",
diff --git a/src/module.rs b/src/module.rs
index 7beb13050..eb8874c4e 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -28,6 +28,7 @@ pub const ALL_MODULES: &[&str] = &[
     "gcloud",
     "git_branch",
     "git_commit",
+    "git_metrics",
     "git_state",
     "git_status",
     "golang",
diff --git a/src/modules/git_metrics.rs b/src/modules/git_metrics.rs
new file mode 100644
index 000000000..833faec34
--- /dev/null
+++ b/src/modules/git_metrics.rs
@@ -0,0 +1,275 @@
+use regex::Regex;
+
+use crate::{
+    config::RootModuleConfig, configs::git_metrics::GitMetricsConfig, formatter::StringFormatter,
+    module::Module,
+};
+
+use super::Context;
+
+/// Creates a module with the current added/deleted lines in the git repository at the
+/// current directory
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let mut module = context.new_module("git_metrics");
+    let config: GitMetricsConfig = GitMetricsConfig::try_load(module.config);
+
+    // As we default to disabled=true, we have to check here after loading our config module,
+    // before it was only checking against whatever is in the config starship.toml
+    if config.disabled {
+        return None;
+    };
+
+    let repo = context.get_repo().ok()?;
+    let repo_root = repo.root.as_ref()?;
+
+    let diff = context
+        .exec_cmd(
+            "git",
+            &[
+                "-C",
+                &repo_root.to_string_lossy(),
+                "--no-optional-locks",
+                "diff",
+                "--shortstat",
+            ],
+        )?
+        .stdout;
+
+    let stats = GitDiff::parse(&diff);
+
+    let parsed = StringFormatter::new(config.format).and_then(|formatter| {
+        formatter
+            .map_style(|variable| match variable {
+                "added_style" => Some(Ok(config.added_style)),
+                "deleted_style" => Some(Ok(config.deleted_style)),
+                _ => None,
+            })
+            .map(|variable| match variable {
+                "added" => Some(Ok(stats.added)),
+                "deleted" => Some(Ok(stats.deleted)),
+                _ => None,
+            })
+            .parse(None)
+    });
+
+    module.set_segments(match parsed {
+        Ok(segments) => segments,
+        Err(error) => {
+            log::warn!("Error in module `git_metrics`:\n{}", error);
+            return None;
+        }
+    });
+
+    Some(module)
+}
+
+/// Represents the parsed output from a git diff.
+struct GitDiff<'a> {
+    added: &'a str,
+    deleted: &'a str,
+}
+
+impl<'a> GitDiff<'a> {
+    /// Returns the first capture group given a regular expression and a string.
+    /// If it fails to get the capture group it will return "0".
+    fn get_matched_str(diff: &'a str, re: &Regex) -> &'a str {
+        match re.captures(diff) {
+            Some(caps) => caps.get(1).unwrap().as_str(),
+            _ => "0",
+        }
+    }
+
+    /// Parses the result of 'git diff --shortstat' as a `GitDiff` struct.
+    pub fn parse(diff: &'a str) -> Self {
+        let added_re = Regex::new(r"(\d+) \w+\(\+\)").unwrap();
+        let deleted_re = Regex::new(r"(\d+) \w+\(\-\)").unwrap();
+
+        Self {
+            added: GitDiff::get_matched_str(diff, &added_re),
+            deleted: GitDiff::get_matched_str(diff, &deleted_re),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::ffi::OsStr;
+    use std::fs::OpenOptions;
+    use std::io::{self, Error, ErrorKind, Write};
+    use std::path::{Path, PathBuf};
+    use std::process::{Command, Stdio};
+
+    use ansi_term::Color;
+
+    use crate::test::ModuleRenderer;
+
+    #[test]
+    fn shows_nothing_on_empty_dir() -> io::Result<()> {
+        let repo_dir = tempfile::tempdir()?;
+        let path = repo_dir.path();
+
+        let actual = render_metrics(path);
+
+        let expected = None;
+
+        assert_eq!(expected, actual);
+        repo_dir.close()
+    }
+
+    #[test]
+    fn shows_added_lines() -> io::Result<()> {
+        let repo_dir = create_repo_with_commit()?;
+        let path = repo_dir.path();
+
+        let the_file = path.join("the_file");
+        let mut the_file = OpenOptions::new().append(true).open(&the_file)?;
+        writeln!(the_file, "Added line")?;
+        the_file.sync_all()?;
+
+        let actual = render_metrics(path);
+
+        let expected = Some(format!(
+            "{} {} ",
+            Color::Green.bold().paint("+1"),
+            Color::Red.bold().paint("-0")
+        ));
+
+        assert_eq!(expected, actual);
+        repo_dir.close()
+    }
+
+    #[test]
+    fn shows_deleted_lines() -> io::Result<()> {
+        let repo_dir = create_repo_with_commit()?;
+        let path = repo_dir.path();
+
+        let file_path = path.join("the_file");
+        write_file(file_path, "First Line\nSecond Line")?;
+
+        let actual = render_metrics(path);
+
+        let expected = Some(format!(
+            "{} {} ",
+            Color::Green.bold().paint("+0"),
+            Color::Red.bold().paint("-1")
+        ));
+
+        assert_eq!(expected, actual);
+        repo_dir.close()
+    }
+
+    #[test]
+    fn shows_all_changes() -> io::Result<()> {
+        let repo_dir = create_repo_with_commit()?;
+        let path = repo_dir.path();
+
+        let file_path = path.join("the_file");
+        write_file(file_path, "\nSecond Line\n\nModified\nAdded")?;
+
+        let actual = render_metrics(path);
+
+        let expected = Some(format!(
+            "{} {} ",
+            Color::Green.bold().paint("+4"),
+            Color::Red.bold().paint("-2")
+        ));
+
+        assert_eq!(expected, actual);
+        repo_dir.close()
+    }
+
+    fn render_metrics(path: &Path) -> Option<String> {
+        ModuleRenderer::new("git_metrics")
+            .config(toml::toml! {
+                [git_metrics]
+                disabled = false
+            })
+            .path(path)
+            .collect()
+    }
+
+    fn run_git_cmd<A, S>(args: A, dir: Option<&Path>, should_succeed: bool) -> io::Result<()>
+    where
+        A: IntoIterator<Item = S>,
+        S: AsRef<OsStr>,
+    {
+        let mut command = Command::new("git");
+        command
+            .args(args)
+            .stdout(Stdio::null())
+            .stderr(Stdio::null())
+            .stdin(Stdio::null());
+
+        if let Some(dir) = dir {
+            command.current_dir(dir);
+        }
+
+        let status = command.status()?;
+
+        if should_succeed && !status.success() {
+            Err(Error::from(ErrorKind::Other))
+        } else {
+            Ok(())
+        }
+    }
+
+    fn write_file(file: PathBuf, text: &str) -> io::Result<()> {
+        let mut file = OpenOptions::new()
+            .write(true)
+            .create(true)
+            .truncate(true)
+            .open(&file)?;
+        writeln!(file, "{}", text)?;
+        file.sync_all()
+    }
+
+    fn create_repo_with_commit() -> io::Result<tempfile::TempDir> {
+        let repo_dir = tempfile::tempdir()?;
+        let path = repo_dir.path();
+        let file = repo_dir.path().join("the_file");
+
+        // Initialize a new git repo
+        run_git_cmd(
+            &[
+                "init",
+                "--quiet",
+                path.to_str().expect("Path was not UTF-8"),
+            ],
+            None,
+            true,
+        )?;
+
+        // Set local author info
+        run_git_cmd(
+            &["config", "--local", "user.email", "starship@example.com"],
+            Some(path),
+            true,
+        )?;
+        run_git_cmd(
+            &["config", "--local", "user.name", "starship"],
+            Some(path),
+            true,
+        )?;
+
+        // Ensure on the expected branch.
+        // If build environment has `init.defaultBranch` global set
+        // it will default to an unknown branch, so need to make & change branch
+        run_git_cmd(
+            &["checkout", "-b", "master"],
+            Some(path),
+            // command expected to fail if already on the expected branch
+            false,
+        )?;
+
+        // Write a file on master and commit it
+        write_file(file, "First Line\nSecond Line\nThird Line")?;
+        run_git_cmd(&["add", "the_file"], Some(path), true)?;
+        run_git_cmd(
+            &["commit", "--message", "Commit A", "--no-gpg-sign"],
+            Some(path),
+            true,
+        )?;
+
+        Ok(repo_dir)
+    }
+}
diff --git a/src/modules/git_state.rs b/src/modules/git_state.rs
index cfd259033..f2d1e1c9d 100644
--- a/src/modules/git_state.rs
+++ b/src/modules/git_state.rs
@@ -337,7 +337,7 @@ mod tests {
 
         // Ensure on the expected branch.
         // If build environment has `init.defaultBranch` global set
-        // it will default to an unknown branch, so neeed to make & change branch
+        // it will default to an unknown branch, so need to make & change branch
         run_git_cmd(
             &["checkout", "-b", "master"],
             Some(path),
diff --git a/src/modules/mod.rs b/src/modules/mod.rs
index f64b016bc..49c746e70 100644
--- a/src/modules/mod.rs
+++ b/src/modules/mod.rs
@@ -18,6 +18,7 @@ mod erlang;
 mod gcloud;
 mod git_branch;
 mod git_commit;
+mod git_metrics;
 mod git_state;
 mod git_status;
 mod golang;
@@ -98,6 +99,7 @@ pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
             "gcloud" => gcloud::module(context),
             "git_branch" => git_branch::module(context),
             "git_commit" => git_commit::module(context),
+            "git_metrics" => git_metrics::module(context),
             "git_state" => git_state::module(context),
             "git_status" => git_status::module(context),
             "golang" => golang::module(context),
@@ -180,6 +182,7 @@ pub fn description(module: &str) -> &'static str {
         "gcloud" => "The current GCP client configuration",
         "git_branch" => "The active branch of the repo in your current directory",
         "git_commit" => "The active commit (and tag if any) of the repo in your current directory",
+        "git_metrics" => "The currently added/deleted lines in your repo",
         "git_state" => "The current git operation, and it's progress",
         "git_status" => "Symbol representing the state of the repo",
         "golang" => "The currently installed version of Golang",