better char debugging experience

src/Corpus.zig

@@ -196,8 +196,8 @@ pub fn testCorpus(allocator: Allocator) !Corpus {
         .gid = math.maxInt(u32),
         .name = "Name" ** 8,
         .gecos = "Gecos" ** 51,
-        .home = "Home" ** 16,
+        .home = "/Hom" ** 16,
-        .shell = "She.LllL" ** 8,
+        .shell = "/She.Lll" ** 8,
     }, User{
         .uid = 100000,
         .gid = 1002,

src/User.zig

@@ -184,7 +184,7 @@ test "User.fromLine" {
         },
         .{
             .line = "žemas:x:0:0:root:/root:/bin/bash",
-            .wantErr = "invalid name 'žemas': invalid character at position 0",
+            .wantErr = "invalid name 'žemas': invalid character 0xC5 at position 0",
         },
         .{
             .line = "root:x:-1:0:root:/root:/bin/bash",

src/unix2db/main.zig

@@ -220,7 +220,7 @@ test "smoke test" {
     };
 
     const exit_code = execute(allocator, stdout.writer(), stderr.writer(), args);
-    if (true) return error.SkipZigTest;
+    //if (true) return error.SkipZigTest;
     try testing.expectEqualStrings("", stderr.items);
     try testing.expectEqual(@as(u8, 0), exit_code);
 }

src/validate.zig

@@ -1,5 +1,6 @@
 const std = @import("std");
 const ascii = std.ascii;
+const BoundedArray = std.BoundedArray;
 
 const ErrCtx = @import("ErrCtx.zig");
 
@@ -13,6 +14,14 @@ pub fn utf8(s: []const u8) error{InvalidRecord}!void {
     }
 }
 
+fn debugChar(c: u8) BoundedArray(u8, 4) {
+    var res = BoundedArray(u8, 4).init(0) catch unreachable;
+    if (ascii.isPrint(c)) {
+        res.writer().print("'{c}'", .{c}) catch unreachable;
+    } else res.writer().print("0x{X}", .{c}) catch unreachable;
+    return res;
+}
+
 // # adduser žmogus
 // adduser: To avoid problems, the username should consist only of letters,
 // digits, underscores, periods, at signs and dashes, and not start with a dash
@@ -24,13 +33,17 @@ pub fn name(s: []const u8, err: *ErrCtx) error{InvalidRecord}!void {
 
     const c0 = s[0];
     if (!(ascii.isAlNum(c0) or c0 == '_' or c0 == '.' or c0 == '@'))
-        return err.returnf("invalid character at position 0", .{}, error.InvalidRecord);
+        return err.returnf(
+            "invalid character {s} at position 0",
+            .{debugChar(c0).constSlice()},
+            error.InvalidRecord,
+        );
 
     for (s[1..]) |c, i| {
         if (!(ascii.isAlNum(c) or c == '_' or c == '.' or c == '@' or c == '-'))
             return err.returnf(
-                "invalid character at position {d}",
+                "invalid character {s} at position {d}",
-                .{i + 2},
+                .{ debugChar(c).constSlice(), i + 2 },
                 error.InvalidRecord,
             );
     }
@@ -59,7 +72,7 @@ pub fn path(s: []const u8, err: *ErrCtx) error{InvalidRecord}!void {
     for (s[1..]) |c, i| {
         if (!(ascii.isAlNum(c) or c == '/' or c == '_' or c == '.' or c == '@' or c == '-'))
             return err.returnf(
-                "invalid character at position {d}",
+                "invalid character 0xD at position {d}",
                 .{i + 2},
                 error.InvalidRecord,
             );
@@ -76,8 +89,8 @@ test "validate name" {
         .{ .name = "all-good" },
         .{ .name = "..." },
         .{ .name = "", .wantErr = "cannot be empty" },
-        .{ .name = "-no-start-dash", .wantErr = "invalid character at position 0" },
+        .{ .name = "-no-start-dash", .wantErr = "invalid character '-' at position 0" },
-        .{ .name = "Herbasž", .wantErr = "invalid character at position 7" },
+        .{ .name = "Herbasž", .wantErr = "invalid character 0xC5 at position 7" },
     };
     for (examples) |tt| {
         var err = ErrCtx{};
@@ -130,8 +143,8 @@ test "validate path" {
         .{ .path = "/" },
         .{ .path = "foo", .wantErr = "must start with /" },
         .{ .path = "", .wantErr = "cannot be empty" },
-        .{ .path = "/path:motiejus", .wantErr = "invalid character at position 6" },
+        .{ .path = "/path:motiejus", .wantErr = "invalid character 0xD at position 6" },
-        .{ .path = "/Herbasž", .wantErr = "invalid character at position 8" },
+        .{ .path = "/Herbasž", .wantErr = "invalid character 0xD at position 8" },
     };
     for (examples) |tt| {
         var err = ErrCtx{};