extract passwd to its own file so its easier to test

src/config.zig

@@ -3,16 +3,10 @@ const builtin = @import("builtin");
 const Allocator = std.mem.Allocator;
 const ArenaAllocator = std.heap.ArenaAllocator;
 const inputpkg = @import("input.zig");
+const passwd = @import("passwd.zig");
 
 const log = std.log.scoped(.config);
 
-/// Used to determine the default shell and directory on Unixes.
-const c = @cImport({
-    @cInclude("sys/types.h");
-    @cInclude("unistd.h");
-    @cInclude("pwd.h");
-});
-
 /// Config is the main config struct. These fields map directly to the
 /// CLI flag names hence we use a lot of `@""` syntax to support hyphens.
 pub const Config = struct {
@@ -172,27 +166,9 @@ pub const Config = struct {
                 break :command;
             } else |_| {}
 
-            var buf: [1024]u8 = undefined;
-            var pw: c.struct_passwd = undefined;
-            var pw_ptr: ?*c.struct_passwd = null;
-            const res = c.getpwuid_r(c.getuid(), &pw, &buf, buf.len, &pw_ptr);
-            if (res != 0) {
-                log.warn("error retrieving pw entry code={d}", .{res});
-                break :command;
-            }
-
-            if (pw_ptr == null) {
-                // Future: let's check if a better shell is available like zsh
-                log.warn("no pw entry to detect default shell, will default to 'sh'", .{});
-                self.command = "sh";
-                break :command;
-            }
-
-            if (pw.pw_shell) |ptr| {
-                const source = std.mem.sliceTo(ptr, 0);
-                const sh = try alloc.alloc(u8, source.len);
-                std.mem.copy(u8, sh, source);
-
+            // Get the shell from the passwd entry
+            const pw = try passwd.get(alloc);
+            if (pw.shell) |sh| {
                 log.debug("default shell src=passwd value={s}", .{sh});
                 self.command = sh;
             }

src/main.zig

@@ -177,6 +177,7 @@ test {
 
     // TODO
     _ = @import("config.zig");
+    _ = @import("passwd.zig");
     _ = @import("cli_args.zig");
     _ = @import("lru.zig");
 }

src/passwd.zig

@@ -0,0 +1,68 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const Allocator = std.mem.Allocator;
+const ArenaAllocator = std.heap.ArenaAllocator;
+
+const log = std.log.scoped(.passwd);
+
+/// Used to determine the default shell and directory on Unixes.
+const c = @cImport({
+    @cInclude("sys/types.h");
+    @cInclude("unistd.h");
+    @cInclude("pwd.h");
+});
+
+// Entry that is retrieved from the passwd API. This only contains the fields
+// we care about.
+pub const Entry = struct {
+    shell: ?[]const u8 = null,
+    home: ?[]const u8 = null,
+};
+
+/// Get the passwd entry for the currently executing user.
+pub fn get(alloc: Allocator) !Entry {
+    var buf: [1024]u8 = undefined;
+    var pw: c.struct_passwd = undefined;
+    var pw_ptr: ?*c.struct_passwd = null;
+    const res = c.getpwuid_r(c.getuid(), &pw, &buf, buf.len, &pw_ptr);
+    if (res != 0) {
+        log.warn("error retrieving pw entry code={d}", .{res});
+        return Entry{};
+    }
+
+    if (pw_ptr == null) {
+        // Future: let's check if a better shell is available like zsh
+        log.warn("no pw entry to detect default shell, will default to 'sh'", .{});
+        return Entry{};
+    }
+
+    var result: Entry = .{};
+
+    if (pw.pw_shell) |ptr| {
+        const source = std.mem.sliceTo(ptr, 0);
+        const sh = try alloc.alloc(u8, source.len);
+        std.mem.copy(u8, sh, source);
+        result.shell = sh;
+    }
+
+    if (pw.pw_dir) |ptr| {
+        const source = std.mem.sliceTo(ptr, 0);
+        const dir = try alloc.alloc(u8, source.len);
+        std.mem.copy(u8, dir, source);
+        result.home = dir;
+    }
+
+    return result;
+}
+
+test {
+    const testing = std.testing;
+    var arena = ArenaAllocator.init(testing.allocator);
+    defer arena.deinit();
+    const alloc = arena.allocator();
+
+    // We should be able to get an entry
+    const entry = try get(alloc);
+    try testing.expect(entry.shell != null);
+    try testing.expect(entry.home != null);
+}