zig fmt: Fix relative paths with . and .. on Windows as well as forward slashes

lib/std/io/buffered_atomic_file.zig

@@ -15,8 +15,12 @@ pub const BufferedAtomicFile = struct {
 
     /// TODO when https://github.com/ziglang/zig/issues/2761 is solved
     /// this API will not need an allocator
-    /// TODO integrate this with Dir API
-    pub fn create(allocator: *mem.Allocator, dest_path: []const u8) !*BufferedAtomicFile {
+    pub fn create(
+        allocator: *mem.Allocator,
+        dir: fs.Dir,
+        dest_path: []const u8,
+        atomic_file_options: fs.Dir.AtomicFileOptions,
+    ) !*BufferedAtomicFile {
         var self = try allocator.create(BufferedAtomicFile);
         self.* = BufferedAtomicFile{
             .atomic_file = undefined,
@@ -26,7 +30,7 @@ pub const BufferedAtomicFile = struct {
         };
         errdefer allocator.destroy(self);
 
-        self.atomic_file = try fs.cwd().atomicFile(dest_path, .{});
+        self.atomic_file = try dir.atomicFile(dest_path, atomic_file_options);
         errdefer self.atomic_file.deinit();
 
         self.file_stream = self.atomic_file.file.outStream();

lib/std/os/windows.zig

@@ -1260,15 +1260,9 @@ pub fn wToPrefixedFileW(s: []const u16) ![PATH_MAX_WIDE:0]u16 {
 pub fn sliceToPrefixedSuffixedFileW(s: []const u8, comptime suffix: []const u16) ![PATH_MAX_WIDE + suffix.len:0]u16 {
     // TODO https://github.com/ziglang/zig/issues/2765
     var result: [PATH_MAX_WIDE + suffix.len:0]u16 = undefined;
-    // > File I/O functions in the Windows API convert "/" to "\" as part of
-    // > converting the name to an NT-style name, except when using the "\\?\"
-    // > prefix as detailed in the following sections.
-    // from https://docs.microsoft.com/en-us/windows/desktop/FileIO/naming-a-file#maximum-path-length-limitation
-    // Because we want the larger maximum path length for absolute paths, we
-    // disallow forward slashes in zig std lib file functions on Windows.
     for (s) |byte| {
         switch (byte) {
-            '/', '*', '?', '"', '<', '>', '|' => return error.BadPathName,
+            '*', '?', '"', '<', '>', '|' => return error.BadPathName,
             else => {},
         }
     }
@@ -1279,6 +1273,17 @@ pub fn sliceToPrefixedSuffixedFileW(s: []const u8, comptime suffix: []const u16)
     };
     const end_index = start_index + try std.unicode.utf8ToUtf16Le(result[start_index..], s);
     if (end_index + suffix.len > result.len) return error.NameTooLong;
+    // > File I/O functions in the Windows API convert "/" to "\" as part of
+    // > converting the name to an NT-style name, except when using the "\\?\"
+    // > prefix as detailed in the following sections.
+    // from https://docs.microsoft.com/en-us/windows/desktop/FileIO/naming-a-file#maximum-path-length-limitation
+    // Because we want the larger maximum path length for absolute paths, we
+    // convert forward slashes to backward slashes here.
+    for (result[0..end_index]) |*elem| {
+        if (elem.* == '/') {
+            elem.* = '\\';
+        }
+    }
     mem.copy(u16, result[end_index..], suffix);
     result[end_index + suffix.len] = 0;
     return result;

src-self-hosted/stage2.zig

@@ -318,11 +318,18 @@ const FmtError = error{
 } || fs.File.OpenError;
 
 fn fmtPath(fmt: *Fmt, file_path: []const u8, check_mode: bool) FmtError!void {
-    if (fmt.seen.exists(file_path)) return;
-    try fmt.seen.put(file_path);
+    // get the real path here to avoid Windows failing on relative file paths with . or .. in them
+    var real_path = fs.realpathAlloc(fmt.allocator, file_path) catch |err| {
+        try stderr.print("unable to open '{}': {}\n", .{ file_path, err });
+        fmt.any_error = true;
+        return;
+    };
+    defer fmt.allocator.free(real_path);
+
+    if (fmt.seen.exists(real_path)) return;
+    try fmt.seen.put(real_path);
 
-    const max = std.math.maxInt(usize);
-    const source_code = fs.cwd().readFileAlloc(fmt.allocator, file_path, max) catch |err| switch (err) {
+    const source_code = fs.cwd().readFileAlloc(fmt.allocator, real_path, self_hosted_main.max_src_size) catch |err| switch (err) {
         error.IsDir, error.AccessDenied => {
             // TODO make event based (and dir.next())
             var dir = try fs.cwd().openDir(file_path, .{ .iterate = true });
@@ -370,7 +377,7 @@ fn fmtPath(fmt: *Fmt, file_path: []const u8, check_mode: bool) FmtError!void {
             fmt.any_error = true;
         }
     } else {
-        const baf = try io.BufferedAtomicFile.create(fmt.allocator, file_path);
+        const baf = try io.BufferedAtomicFile.create(fmt.allocator, fs.cwd(), real_path, .{});
         defer baf.destroy();
 
         const anything_changed = try std.zig.render(fmt.allocator, baf.stream(), tree);