Revert "Merge pull request #14661 from evacchi/zig-wasi-preopens"

This reverts commit 772a0eb68a, reversing
changes made to 0bb178bbb2.

This needs a rebase against master branch - it has build-breaking merge
conflicts. I also added a "changes requested" review on the original
pull request.

lib/std/Build/CompileStep.zig

@@ -1555,9 +1555,7 @@ fn make(step: *Step) !void {
                     try zig_args.append("--test-cmd");
                     try zig_args.append(bin_name);
                     try zig_args.append("--test-cmd");
-                    try zig_args.append("--mapdir=/::.");
+                    try zig_args.append("--dir=.");
-                    try zig_args.append("--test-cmd");
-                    try zig_args.append("--mapdir=/tmp::/tmp");
                     try zig_args.append("--test-cmd-bin");
                 } else {
                     try zig_args.append("--test-no-exec");

lib/std/fs/test.zig

@@ -13,11 +13,6 @@ const File = std.fs.File;
 const tmpDir = testing.tmpDir;
 const tmpIterableDir = testing.tmpIterableDir;
 
-// ensure tests for fs/wasi.zig are run
-comptime {
-    _ = std.fs.wasi;
-}
-
 test "Dir.readLink" {
     var tmp = tmpDir(.{});
     defer tmp.cleanup();

lib/std/fs/wasi.zig

@@ -9,7 +9,6 @@ const Allocator = mem.Allocator;
 const wasi = std.os.wasi;
 const fd_t = wasi.fd_t;
 const prestat_t = wasi.prestat_t;
-const testing = std.testing;
 
 pub const Preopens = struct {
     // Indexed by file descriptor number.
@@ -23,30 +22,6 @@ pub const Preopens = struct {
         }
         return null;
     }
-
-    pub fn findDir(p: Preopens, full_path: []const u8, flags: std.fs.Dir.OpenDirOptions) std.fs.Dir.OpenError!std.fs.Dir {
-        if (p.names.len <= 2)
-            return std.fs.Dir.OpenError.BadPathName; // there are no preopens
-
-        var prefix: []const u8 = "";
-        var fd: usize = 0;
-        for (p.names) |preopen, i| {
-            if (i > 2 and wasiPathPrefixMatches(preopen, full_path)) {
-                if (preopen.len > prefix.len) {
-                    prefix = preopen;
-                    fd = i;
-                }
-            }
-        }
-
-        // still no match
-        if (fd == 0) {
-            return std.fs.Dir.OpenError.FileNotFound;
-        }
-        const d = std.fs.Dir{ .fd = @intCast(os.fd_t, fd) };
-        const rel = full_path[prefix.len + 1 .. full_path.len];
-        return d.openDirWasi(rel, flags);
-    }
 };
 
 pub fn preopensAlloc(gpa: Allocator) Allocator.Error!Preopens {
@@ -79,86 +54,3 @@ pub fn preopensAlloc(gpa: Allocator) Allocator.Error!Preopens {
         names.appendAssumeCapacity(name);
     }
 }
-
-fn wasiPathPrefixMatches(prefix: []const u8, path: []const u8) bool {
-    if (path[0] != '/' and prefix.len == 0)
-        return true;
-
-    if (path.len < prefix.len)
-        return false;
-
-    if (prefix.len == 1) {
-        return prefix[0] == path[0];
-    }
-
-    if (!std.mem.eql(u8, path[0..prefix.len], prefix)) {
-        return false;
-    }
-
-    return path.len == prefix.len or
-        path[prefix.len] == '/';
-}
-
-test "preopens" {
-    if (builtin.os.tag != .wasi or builtin.link_libc) return error.SkipZigTest;
-
-    // lifted from `testing`
-    const random_bytes_count = 12;
-    const buf_size = 256;
-    const path = "/tmp";
-    const tmp_file_name = "file.txt";
-    const nonsense = "nonsense";
-
-    var random_bytes: [random_bytes_count]u8 = undefined;
-    var buf: [buf_size]u8 = undefined;
-
-    std.crypto.random.bytes(&random_bytes);
-    const sub_path = std.fs.base64_encoder.encode(&buf, &random_bytes);
-
-    // find all preopens
-    const allocator = std.heap.page_allocator;
-    var wasi_preopens = try std.fs.wasi.preopensAlloc(allocator);
-
-    // look for the exact "/tmp" preopen match
-    const fd = std.fs.wasi.Preopens.find(wasi_preopens, path) orelse unreachable;
-    const base_dir = std.fs.Dir{ .fd = fd };
-
-    var tmp_path = base_dir.makeOpenPath(sub_path, .{}) catch
-        @panic("unable to make tmp dir for testing: /tmp/<rand-path>");
-
-    defer tmp_path.close();
-    defer tmp_path.deleteTree(sub_path) catch {};
-
-    // create a file under /tmp/<rand>/file.txt with contents "nonsense"
-    try tmp_path.writeFile(tmp_file_name, nonsense);
-
-    // now look for the file as a single path
-    var tmp_dir_path_buf: [buf_size]u8 = undefined;
-    const tmp_dir_path = try std.fmt.bufPrint(&tmp_dir_path_buf, "{s}/{s}", .{ path, sub_path });
-
-    // find "/tmp/<rand>" using `findDir()`
-    const tmp_file_dir = try wasi_preopens.findDir(tmp_dir_path, .{});
-
-    const text = try tmp_file_dir.readFile(tmp_file_name, &buf);
-
-    // ensure the file contents match "nonsense"
-    try testing.expect(std.mem.eql(u8, nonsense, text));
-}
-
-test "wasiPathPrefixMatches" {
-    try testing.expect(wasiPathPrefixMatches("/", "/foo"));
-    try testing.expect(wasiPathPrefixMatches("/testcases", "/testcases/test.txt"));
-    try testing.expect(wasiPathPrefixMatches("", "foo"));
-    try testing.expect(wasiPathPrefixMatches("foo", "foo"));
-    try testing.expect(wasiPathPrefixMatches("foo", "foo/bar"));
-    try testing.expect(!wasiPathPrefixMatches("bar", "foo/bar"));
-    try testing.expect(!wasiPathPrefixMatches("bar", "foo"));
-    try testing.expect(wasiPathPrefixMatches("foo", "foo/bar"));
-    try testing.expect(!wasiPathPrefixMatches("fooo", "foo"));
-    try testing.expect(!wasiPathPrefixMatches("foo", "fooo"));
-    try testing.expect(!wasiPathPrefixMatches("foo/bar", "foo"));
-    try testing.expect(!wasiPathPrefixMatches("bar/foo", "foo"));
-    try testing.expect(wasiPathPrefixMatches("/foo", "/foo"));
-    try testing.expect(wasiPathPrefixMatches("/foo", "/foo"));
-    try testing.expect(wasiPathPrefixMatches("/foo", "/foo/"));
-}