From 8aaceba4845bcb433a9a93a2cb4e33d603144658 Mon Sep 17 00:00:00 2001
From: torque <torque@epicyclic.dev>
Date: Tue, 18 Jun 2024 18:32:16 -0700
Subject: [PATCH] parser.value.convertTo: add field converter concept

It is convenient to be able to have custom logic for a specific field
on a given struct without having to write a function to manually reify
the whole thing from scratch.
---
 src/parser/value.zig | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/parser/value.zig b/src/parser/value.zig
index 9fd5603..0919771 100644
--- a/src/parser/value.zig
+++ b/src/parser/value.zig
@@ -68,6 +68,10 @@ pub const Value = union(enum) {
     map: Map,
     inline_map: Map,
 
+    pub fn FieldConverter(comptime T: type) type {
+        return *const fn (Value, std.mem.Allocator, Options) error{BadValue}!T;
+    }
+
     pub fn convertTo(self: Value, comptime T: type, allocator: std.mem.Allocator, options: Options) !T {
         switch (@typeInfo(T)) {
             .Void => {
@@ -215,7 +219,11 @@ pub const Value = union(enum) {
                         var use_count: usize = 0;
                         inline for (stt.fields) |field| {
                             if (map.get(field.name)) |val| {
-                                @field(result, field.name) = try val.convertTo(field.type, allocator, options);
+                                if (comptime hasFn(T, "niceFieldConverter") and T.niceFieldConverter(field.name) != null) {
+                                    @field(result, field.name) = try T.niceFieldConverter(field.name).?(val, allocator, options);
+                                } else {
+                                    @field(result, field.name) = try val.convertTo(field.type, allocator, options);
+                                }
                                 use_count += 1;
                             } else if (options.allow_omitting_default_values) {
                                 if (comptime field.default_value) |def|