1 files changed, 56 insertions, 1 deletions
diff --git a/src/fs.zig b/src/fs.zig
index 30ad9c43..7695d497 100644
--- a/src/fs.zig
+++ b/src/fs.zig
@@ -732,6 +732,59 @@ pub fn dotRelative(word: []const u8) bool {
 /// Where a path really is on the host, and whether it is a directory. The
 /// path may lie in a mount this editor serves, so the turn is given up for
 /// the syscalls: another thread answers them.
+/// A path's leading `~` -- alone, or before `/` or `:` (`~/x:12`) -- is the
+/// home directory: $HOME, else the passwd entry's. `~user/...` is that
+/// user's. As in a shell, `~` is home even beside a file named `~` in the
+/// current directory. Every entry point that takes a path the user typed
+/// runs it through here: look (B3 and 9P), name, Save, ThemeFile, DumpDir,
+/// Restore, a forwarded `pardes ~/x`. The path itself when there is no
+/// `~` to expand, or no home for it.
+pub fn expandHome(path: []const u8, out: *[4096]u8) []const u8 {
+    if (comptime !pardes.hosted) return path;
+    return expandHomeFrom(path, out, std.c.getenv("HOME"));
+}
+
+/// expandHome with HOME given (null: unset), so a test need not change the
+/// process's environment, which a child spawned later reads.
+fn expandHomeFrom(path: []const u8, out: *[4096]u8, env_home: ?[*:0]const u8) []const u8 {
+    if (path.len == 0 or path[0] != '~') return path;
+    const end = std.mem.indexOfAny(u8, path, "/:") orelse path.len;
+    const home = (if (end == 1) homeDir(env_home) else userHome(path[1..end])) orelse return path;
+    const trimmed = std.mem.trimEnd(u8, home, "/");
+    const rest = path[end..];
+    if (trimmed.len == 0 and (rest.len == 0 or rest[0] != '/')) return std.fmt.bufPrint(out, "/{s}", .{rest}) catch path;
+    return std.fmt.bufPrint(out, "{s}{s}", .{ trimmed, rest }) catch path;
+}
+
+fn homeDir(env_home: ?[*:0]const u8) ?[]const u8 {
+    if (env_home) |h| if (h[0] != 0) return std.mem.span(h);
+    const pw = std.c.getpwuid(std.c.getuid()) orelse return null;
+    return std.mem.span(pw.dir orelse return null);
+}
+
+fn userHome(name: []const u8) ?[]const u8 {
+    var z: [256]u8 = undefined;
+    const name_z = std.fmt.bufPrintSentinel(&z, "{s}", .{name}, 0) catch return null;
+    const pw = std.c.getpwnam(name_z) orelse return null;
+    return std.mem.span(pw.dir orelse return null);
+}
+
+test "a leading ~ is home, from HOME or else the passwd entry" {
+    var out: [4096]u8 = undefined;
+    const home = homeDir(std.c.getenv("HOME")) orelse return error.SkipZigTest;
+    var want: [4096]u8 = undefined;
+    try std.testing.expectEqualStrings(try std.fmt.bufPrint(&want, "{s}/x:12", .{std.mem.trimEnd(u8, home, "/")}), expandHome("~/x:12", &out));
+    try std.testing.expectEqualStrings(std.mem.trimEnd(u8, home, "/"), expandHome("~", &out));
+    try std.testing.expectEqualStrings("a/~/b", expandHome("a/~/b", &out));
+    try std.testing.expectEqualStrings("~no-such-user-pardes/x", expandHome("~no-such-user-pardes/x", &out));
+    try std.testing.expectEqualStrings("/", expandHome("~root", &out)[0..1]);
+
+    // HOME unset: the passwd entry's home.
+    const pw = std.c.getpwuid(std.c.getuid()) orelse return error.SkipZigTest;
+    var from_passwd: [4096]u8 = undefined;
+    try std.testing.expectEqualStrings(try std.fmt.bufPrint(&from_passwd, "{s}/y", .{std.mem.trimEnd(u8, std.mem.span(pw.dir.?), "/")}), expandHomeFrom("~/y", &out, null));
+}
+
 pub fn resolveOs(path: []const u8, out: *[4096]u8) ?Resolved {
     if (comptime !platform_has_fs) return null;
     var z: [4096]u8 = undefined;
@@ -1171,7 +1224,9 @@ pub fn readFile(gpa: std.mem.Allocator, path: []const u8) ![]u8 {
 
 /// Restore first tries a relative argument under the default dump directory,
 /// then preserves the ordinary file lookup. Absolute paths remain verbatim.
-pub fn readRestore(gpa: std.mem.Allocator, path: []const u8, dir_setting: []const u8) ![]u8 {
+pub fn readRestore(gpa: std.mem.Allocator, typed: []const u8, dir_setting: []const u8) ![]u8 {
+    var home_buf: [4096]u8 = undefined;
+    const path = expandHome(typed, &home_buf);
     var dir_buf: [4096]u8 = undefined;
     const dir = @import("dump.zig").directory(&dir_buf, dir_setting);
     return readRestoreIn(gpa, path, dir);