mod(zlog): pretty printing for user defined types

src/main.zig

@@ -1,10 +1,17 @@
 const std = @import("std");
 const zlog = @import("zlog");
 
+pub const std_options = zlog.std_options;
+
 const Options = enum {
     a,
     b,
     c,
+
+    // copy and paste this function into your user defined types to enable pretty printing for these types
+    pub fn format(value: @This(), comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) anyerror!void {
+        try zlog.pretty_format(value, fmt, options, writer);
+    }
 };
 
 const Struct = struct {
@@ -14,44 +21,17 @@ const Struct = struct {
     d: []const u8 = "string",
     e: Options = Options.b,
 
-    // pub fn format(value: Struct, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) !void {
-    //     // TODO: make the creation of this function comptime
-    //     try writer.writeAll("main.Struct{ ");
-    //     try writer.writeAll(".a: usize = ");
-    //     try std.fmt.formatIntValue(value.a, fmt, options, writer);
-    //     try writer.writeAll(", ");
-
-    //     try writer.writeAll(".b: bool = ");
-    //     try std.fmt.formatBuf(if (value.b) "true" else "false", options, writer);
-    //     try writer.writeAll(", ");
-
-    //     try writer.writeAll(".c: [5]u16 = ");
-    //     try std.fmt.format(writer, "{any}", .{value.c});
-    //     try writer.writeAll(", ");
-
-    //     try writer.writeAll(".d: []const u8 = ");
-    //     try std.fmt.format(writer, "\"{s}\"", .{value.d});
-    //     try writer.writeAll(", ");
-
-    //     try writer.writeAll(".e: main.Options = ");
-    //     try std.fmt.format(writer, "{any}", .{value.e});
-
-    //     try writer.writeAll(" }");
-    // }
-
-    // TODO: can this become comptime entirely? - i.e. create the entire struct through a helper function and provide the created one with the format function already attached?
-    pub fn format(value: Struct, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) anyerror!void {
-        try zlog.generic_format(value, fmt, options, writer);
+    // same function as above...
+    pub fn format(value: @This(), comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) anyerror!void {
+        try zlog.pretty_format(value, fmt, options, writer);
     }
 };
 
-pub const std_options = zlog.std_options;
-
 pub fn main() void {
     // initialize zlog with the scope of `main`
     const log = std.log.scoped(.main);
     // NOTE: the scope of `default` will result in no scoping being printed in
-    // the resulting output
+    // the resulting output (default behavior of `std.log.defaultLog`)
 
     // some variables to log
     const int_var = 42;

src/zlog.zig

@@ -1,7 +1,5 @@
 const std = @import("std");
 
-const max_depth = 5;
-
 // pub fn format(value: ?, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) !void
 // TODO: provide comptime helper function to add format function for user types:
 // - pretty printing
@@ -30,7 +28,7 @@ fn logFn(
     // - should there be spacing?
     // - should the messages be aligned (left, center, right)?
     const level_txt = comptime message_level.asText();
-    const prefix2 = if (scope == .default) ":\t" else "(" ++ @tagName(scope) ++ "):\t";
+    const prefix = if (scope == .default) ":\t" else "(" ++ @tagName(scope) ++ "):\t";
     const stderr = std.io.getStdErr().writer();
     var bw = std.io.bufferedWriter(stderr);
     const writer = bw.writer();
@@ -38,51 +36,65 @@ fn logFn(
     std.debug.lockStdErr();
     defer std.debug.unlockStdErr();
     nosuspend {
-        writer.print(level_txt ++ prefix2 ++ format ++ "\n", args) catch return;
+        writer.print(level_txt ++ prefix ++ format ++ "\n", args) catch return;
         bw.flush() catch return;
     }
 }
 
-pub fn generic_format(object: anytype, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) !void {
-    _ = fmt;
-    _ = options;
+pub fn pretty_format(object: anytype, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype) !void {
+    try inner_format(object, fmt, options, writer, 0);
+}
+
+fn inner_format(object: anytype, comptime fmt: []const u8, options: std.fmt.FormatOptions, writer: anytype, comptime depth: u8) !void {
     const Object = @TypeOf(object);
     const object_info = @typeInfo(Object);
     switch (object_info) {
         .Struct => |s| {
             try writer.writeAll(@typeName(Object));
-            try writer.writeAll(" = {\n");
+            try writer.writeAll(" = struct {\n");
             inline for (s.fields) |field| {
-                try writer.writeAll("\t .");
+                try writer.writeAll("\t" ** (depth + 1));
+                try writer.writeAll(".");
                 try writer.writeAll(field.name);
                 try writer.writeAll(" = ");
                 // TODO check corresponding type and try to adapt fmt accordingly!
-                try std.fmt.format(writer, "{any}", .{@field(object, field.name)});
+                // TODO: pass along the already parsed formatting options too
+                try inner_format(@field(object, field.name), fmt, options, writer, depth + 1);
                 try writer.writeAll(",\n");
             }
+            try writer.writeAll("\t" ** depth);
             try writer.writeAll("}");
         },
-        else => {},
-    }
-}
-
-pub fn enhance_format(comptime object: type) type {
-    // TODO: append a function to the type if it is a user defined type
-
-    // NOTE: this has the clear disadvantage that the type is not the same anymore! (but maybe this is still fine)
-    const object_info = @typeInfo(object);
-    switch (object_info) {
-        .Struct => |s| {
-            return @Type(.{
-                .Struct = .{
-                    .layout = .auto,
-                    .fields = s.fields,
-                    .decls = s.decls,
-                    .is_tuple = false,
-                },
-            });
+        .Enum => |e| {
+            try writer.writeAll(@typeName(Object));
+            try writer.writeAll(" = enum {\n");
+            inline for (e.fields) |field| {
+                try writer.writeAll("\t" ** (depth + 1));
+                try writer.writeAll(field.name);
+                try writer.writeAll(",\n");
+            }
+            try writer.writeAll("\t" ** depth);
+            try writer.writeAll("} = ");
+            try writer.writeAll(@tagName(object));
+        },
+        // TODO: implement prett_printing for other user defined types (`union` and `vector`)
+        // TODO: recognize []const u8 types and print them as strings
+        .Array => |a| {
+            if (a.child == @TypeOf([:0]const u8)) {
+                try std.fmt.format(writer, "\"{s}\"", .{object});
+            } else {
+                try std.fmt.format(writer, "[]{s}: {any}", .{ @typeName(a.child), object });
+            }
+        },
+        .Vector => |v| {
+            if (v.child == @TypeOf([:0]const u8)) {
+                try std.fmt.format(writer, "\"{s}\"", .{object});
+            } else {
+                try std.fmt.format(writer, "[]{s}: {any}", .{ @typeName(v.child), object });
+            }
+        },
+        else => {
+            try std.fmt.format(writer, "{any}", .{object});
         },
-        else => {},
     }
-    return object;
 }