From b460ca24aba5027def60e56effd87fce24d09e4b Mon Sep 17 00:00:00 2001
From: dweiller <4678790+dweiller@users.noreply.github.com>
Date: Sun, 21 Jul 2024 15:05:31 +1000
Subject: [PATCH] add install-parent build option

---
 build.zig | 15 +++++++++++++++
 zigup.zig | 48 ++++++++++++++++++++++++++++++++----------------
 2 files changed, 47 insertions(+), 16 deletions(-)

diff --git a/build.zig b/build.zig
index 62579c1..aaeaa7f 100644
--- a/build.zig
+++ b/build.zig
@@ -11,8 +11,23 @@ pub fn build(b: *std.Build) !void {
         "Default compiler installation directory (default: zig)",
     ) orelse "zig";
 
+    const InstallParent = enum { home, @"exe-dir" };
+    const install_parent: ?InstallParent = b.option(
+        InstallParent,
+        "install-parent",
+        "Parent of default installation directory, ignored if '-Ddefault-dir' is an absolute path",
+    ) orelse if (std.fs.path.isAbsolute(default_dir))
+        null
+    else switch (target.result.os.tag) {
+        .windows => .@"exe-dir",
+        else => .home,
+    };
+
     const build_options = b.addOptions();
     build_options.addOption([]const u8, "default_dir", default_dir);
+    if (install_parent) |dir| {
+        build_options.addOption(InstallParent, "install_parent", dir);
+    }
 
     const zigup_exe_native = blk: {
         const exe = addZigupExe(b, target, optimize, build_options);
diff --git a/zigup.zig b/zigup.zig
index 688001e..18a0c2d 100644
--- a/zigup.zig
+++ b/zigup.zig
@@ -120,27 +120,43 @@ fn ignoreHttpCallback(request: []const u8) void {
     _ = request;
 }
 
-fn getHomeDir() ![]const u8 {
-    return std.posix.getenv("HOME") orelse {
-        std.log.err("cannot find install directory, $HOME environment variable is not set", .{});
-        return error.MissingHomeEnvironmentVariable;
-    };
-}
-
 fn allocInstallDirString(allocator: Allocator) ![]const u8 {
     // TODO: maybe support ZIG_INSTALL_DIR environment variable?
     // TODO: maybe support a file on the filesystem to configure install dir?
-    if (builtin.os.tag == .windows) {
-        const self_exe_dir = try std.fs.selfExeDirPathAlloc(allocator);
-        defer allocator.free(self_exe_dir);
-        return std.fs.path.join(allocator, &.{ self_exe_dir, build_options.default_dir });
+
+    if (comptime std.fs.path.isAbsolute(build_options.default_dir)) {
+        // copy wouldn't be needed, but makes calling code simpler
+        return allocator.dupe(u8, build_options.default_dir);
     }
-    const home = try getHomeDir();
-    if (!std.fs.path.isAbsolute(home)) {
-        std.log.err("$HOME environment variable '{s}' is not an absolute path", .{home});
-        return error.BadHomeEnvironmentVariable;
+
+    switch (build_options.install_parent) {
+        .@"exe-dir" => {
+            const self_exe_dir = try std.fs.selfExeDirPathAlloc(allocator);
+            defer allocator.free(self_exe_dir);
+            return std.fs.path.join(allocator, &.{ self_exe_dir, build_options.default_dir });
+        },
+        .home => {
+            const home = switch (builtin.os.tag) {
+                .windows => std.process.getEnvVarOwned(allocator, "HOMEPATH") catch |e| switch (e) {
+                    error.EnvironmentVariableNotFound => {
+                        std.log.err("cannot find isntall directory %HOMEPATH% environment variable is not set", .{});
+                        return error.AlreadyReportedk;
+                    },
+                    else => |err| return err,
+                },
+                else => std.posix.getenv("HOME") orelse {
+                    std.log.err("cannot find install directory, $HOME environment variable is not set", .{});
+                    return error.AlreadyReported;
+                },
+            };
+            const env = if (builtin.os.tag == .windows) "%HOMEPATH%" else "$HOME";
+            if (!std.fs.path.isAbsolute(home)) {
+                std.log.err(env ++ " environment variable '{s}' is not an absolute path", .{home});
+                return error.AlreadyReported;
+            }
+            return std.fs.path.join(allocator, &[_][]const u8{ home, build_options.default_dir });
+        },
     }
-    return std.fs.path.join(allocator, &[_][]const u8{ home, build_options.default_dir });
 }
 const GetInstallDirOptions = struct {
     create: bool,