om health: Add homebrew check

The homebrew check is disabled by default, but can be enabled through om configuration (YAML or nix).

Author: niksingh710

crates/omnix-common/src/check.rs

@@ -1,9 +1,22 @@
 //! Prerequisite checks for the Omnix project.
 
-use which::which;
+use std::path::PathBuf;
+use which::{which, Error};
 
 /// Check if Nix is installed.
 pub fn nix_installed() -> bool {
-    let out = which("nix");
-    out.is_ok()
+    which_strict("nix").is_some()
+}
+
+/// Check if a binary is available in the system's PATH and return its path.
+/// Returns None if the binary is not found, panics on unexpected errors.
+pub fn which_strict(binary: &str) -> Option<PathBuf> {
+    match which(binary) {
+        Ok(path) => Some(path),
+        Err(Error::CannotFindBinaryPath) => None,
+        Err(e) => panic!(
+            "Unexpected error while searching for binary '{}': {:?}",
+            binary, e
+        ),
+    }
 }

crates/omnix-health/src/check/homebrew.rs

@@ -0,0 +1,85 @@
+use nix_rs::{flake::url::FlakeUrl, info::NixInfo};
+use omnix_common::check::which_strict;
+use serde::{Deserialize, Serialize};
+
+use crate::traits::{Check, CheckResult, Checkable};
+
+/// Check if Homebrew is installed
+#[derive(Default, Debug, Serialize, Deserialize, Clone)]
+#[serde(default, rename_all = "kebab-case")]
+pub struct Homebrew {
+    pub(crate) enable: bool,
+    pub(crate) required: bool,
+}
+
+impl Checkable for Homebrew {
+    fn check(
+        &self,
+        nix_info: &NixInfo,
+        _flake_url: Option<&FlakeUrl>,
+    ) -> Vec<(&'static str, Check)> {
+        let mut checks = vec![];
+
+        if self.enable && matches!(nix_info.nix_env.os, nix_rs::env::OS::MacOS { .. }) {
+            checks.push((
+                "homebrew-check",
+                installation_check(&HomebrewInstall::detect(), self.required),
+            ));
+        }
+
+        checks
+    }
+}
+
+/// Information about user's homebrew installation.
+#[derive(Debug)]
+pub struct HomebrewInstall {
+    /// The path to the Homebrew binary.
+    pub bin_path: std::path::PathBuf,
+}
+
+impl HomebrewInstall {
+    /// Detect homebrew installation.
+    pub fn detect() -> Option<Self> {
+        which_strict("brew").map(|bin_path| HomebrewInstall { bin_path })
+    }
+}
+
+/// Create a [Check] for Homebrew installation
+fn installation_check(homebrew_result: &Option<HomebrewInstall>, required: bool) -> Check {
+    let nix_setup_url = "https://github.com/juspay/nixos-unified-template";
+
+    Check {
+        title: "Homebrew installation".to_string(),
+        info: format!(
+            "Homebrew binary: {}",
+            homebrew_result
+                .as_ref()
+                .map(|h| format!("Found at {:?}", h.bin_path))
+                .unwrap_or_else(|| "Not found".to_string())
+        ),
+        result: match homebrew_result {
+            Some(homebrew) => CheckResult::Red {
+                msg: format!(
+                    "Homebrew is installed at {:?}. Consider using Nix for better reproducibility",
+                    homebrew.bin_path
+                ),
+                suggestion: format!(
+                    "Managing packages with Nix, rather than Homebrew, provides better reproducibility and integration. See <{}>\n\n{}",
+                    nix_setup_url,
+                    HOMEBREW_REMOVAL_INSTRUCTIONS
+                ),
+            },
+            None => CheckResult::Green,
+        },
+        required,
+    }
+}
+
+/// A string containing step-by-step removal commands and migration advice.
+const HOMEBREW_REMOVAL_INSTRUCTIONS: &str = r#"To completely remove Homebrew from your system:
+
+- **Uninstall Homebrew and all packages:**
+   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/uninstall.sh)"
+
+For a safer migration, consider using 'brew list' to inventory your packages before removal, then install equivalents via Nix."#;

crates/omnix-health/src/check/mod.rs

@@ -2,6 +2,7 @@
 pub mod caches;
 pub mod direnv;
 pub mod flake_enabled;
+pub mod homebrew;
 pub mod max_jobs;
 pub mod nix_version;
 pub mod rosetta;

crates/omnix-health/src/lib.rs

@@ -10,6 +10,7 @@ use check::shell::ShellCheck;
 use colored::Colorize;
 
 use check::direnv::Direnv;
+use check::homebrew::Homebrew;
 use json::HealthOutput;
 use nix_rs::command::NixCmd;
 use nix_rs::env::OS;
@@ -39,6 +40,7 @@ pub struct NixHealth {
     pub trusted_users: TrustedUsers,
     pub caches: Caches,
     pub direnv: Direnv,
+    pub homebrew: Homebrew,
     pub shell: ShellCheck,
 }
 
@@ -57,6 +59,7 @@ impl<'a> IntoIterator for &'a NixHealth {
             &self.trusted_users,
             &self.caches,
             &self.direnv,
+            &self.homebrew,
             &self.shell,
         ];
         items.into_iter()

doc/src/history.md

@@ -3,7 +3,9 @@
 ## 1.0.4 (UNRELEASED)
 
 - `om ci`: Allow impure builds through `impure = true;` setting in `om.yaml` (#445)
-- `om health`: Fix DetSys installer hijacking its own version into `nix --version` causing false Nix version detection. (#458)
+- `om health`
+  - Fix DetSys installer hijacking its own version into `nix --version` causing false Nix version detection. (#458)
+  - Add homebrew check (disabled by default) (#459)
 
 ## 1.0.3 (2025-03-17) {#1.0.3}
 

doc/src/om/health.md

@@ -20,8 +20,10 @@ The `om health` command checks the health of your Nix install. Furthermore, indi
 | Direnv: installed and activated        | Yes                          |
 | Dotfiles are managed by Nix            | Yes                          |
 | Min RAM / Disk space                   | Yes                          |
+| Homebrew install detection (disabled by default)[^macos] | Yes                |
 
 [^ros]: This check is only performed on macOS with Apple Silicon.
+[^macos]: This check is only performed on  macOS.
 
 Note that some checks are considered non-essential. For eg., the disk space check looks for 1TB+ disk space, but if the user is on a laptop with 256GB SSD, the check will report a warning instead of failing. This can also be configured in per-project basis from `flake.nix` (see below).
 
@@ -74,6 +76,9 @@ caches:
 direnv:
   enable: true
   required: false
+homebrew:
+  enable: false
+  required: false
 shell:
   enable: true
   required: false

om.yaml

@@ -65,6 +65,8 @@ health:
         - https://om.cachix.org
     direnv:
       required: true
+    homebrew:
+      enable: true
 develop:
   default:
     readme: |