From 31b6eecdecf4c09729269fe812c5bbbd28e4e3eb Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mikael=20L=C3=B6vqvist?= <mikael.lovqvist.mail@gmail.com>
Date: Thu, 9 Apr 2026 19:17:57 +0200
Subject: [PATCH] Added coercing system to field configuration, revised some of
 the data validation errors

---
 experiments/config.mjs              | 19 ++++++++++++--
 source/data/field-configuration.mjs | 39 +++++++++++++++++++++--------
 source/errors.mjs                   | 20 ++++++++++++---
 3 files changed, 62 insertions(+), 16 deletions(-)

diff --git a/experiments/config.mjs b/experiments/config.mjs
index 2da6ad8..ed2c988 100644
--- a/experiments/config.mjs
+++ b/experiments/config.mjs
@@ -6,11 +6,26 @@ function mandatory_anything(value) {
 }
 
 
-const fc = new Field_Configuration('Some_Field', mandatory_anything, 'Anything defined');
+function string_coercion_function(value) {
+	if (value === undefined) {
+		throw new Error('Undefined not allowed');
+	}
+	return String(value);
+}
 
 
+
+const fc = new Field_Configuration('Some_Field', null, string_coercion_function, 'Anything that could be a string');
+
 console.log(fc.check_validation(undefined));
 console.log(fc.check_validation(true));
 
+console.log([ fc.coerce(123) ]);
+console.log([ fc.coerce(true) ]);
+
+console.log([ fc.load(undefined, 'Some configuration') ]);
+console.log([ fc.load(true) ]);
+
+
 //fc.validate(undefined);
-fc.validate(undefined, 'New thingamabob object');
+console.log(fc.load(undefined, 'New thingamabob object'));
diff --git a/source/data/field-configuration.mjs b/source/data/field-configuration.mjs
index 9516d28..219a99b 100644
--- a/source/data/field-configuration.mjs
+++ b/source/data/field-configuration.mjs
@@ -1,24 +1,43 @@
-import { Invalid_Data } from '@efforting.tech/errors';
+import { Data_Validation_Failed, Data_Coercion_Failed } from '@efforting.tech/errors';
 
 export class Field_Configuration {
-	constructor(name, validator=null, expected=undefined) {
-		Object.assign(this, { name, validator, expected });
+	constructor(name, validation_function=null, coercion_function=null, expected_description=undefined) {
+		Object.assign(this, { name, validation_function, coercion_function, expected_description });
 	}
 
 	check_validation(value) {
-		const { validator } = this;
-
-		return !validator || validator(value);
+		const { validation_function } = this;
+		return !validation_function || validation_function(value);
 	}
 
 	validate(value, target=undefined) {
-		const { validator, name, expected } = this;
+		const { validation_function, name, expected_description } = this;
 		if (!this.check_validation(value)) {
-			throw new Invalid_Data({
-				name, validator, value,
-				target, expected,
+			throw new Data_Validation_Failed({
+				name, validation_function, value,
+				target, expected_description,
 			});
 		}
 	}
 
+	coerce(value, target=undefined) {
+		const { coercion_function, name, expected_description } = this;
+		try {
+			return coercion_function ? coercion_function(value) : value;
+		} catch (e) {
+			throw new Data_Coercion_Failed({
+				name, coercion_function, value,
+				target, expected_description,
+				upstream_error: e,
+			})
+		}
+	}
+
+	load(value, target=undefined) {
+		const coerced_value = this.coerce(value, target);
+		this.validate(coerced_value, target);
+		return coerced_value;
+	}
+
+
 }
diff --git a/source/errors.mjs b/source/errors.mjs
index 37622b0..aeed2c6 100644
--- a/source/errors.mjs
+++ b/source/errors.mjs
@@ -2,17 +2,29 @@ import { inspect } from 'node:util';
 
 // § GROUP: Configuration field errors
 
-export class Invalid_Data extends Error {
+export class Data_Validation_Failed extends Error {
 	constructor(data) {
-		const { value, target, expected, validator, name } = data;
+		const { value, target, expected_description, validation_function, name, upstream_error } = data;
 		const type = value === null ? 'null' : typeof value;
 		const target_info = target ? inspect(target) : 'unknown target';
-		const expected_desc = expected ?? `data that would pass validation using ${validator}`;
-		super(`Data validation failed for field "${name}" of ${target_info}. Encountered data of type "${type}" while expecting "${expected_desc}".`);
+		const expected_desc = expected_description ?? `data that would pass validation using ${validation_function}`;
+		const upstream_error_description = upstream_error ? ` Upstream error was: ${upstream_error}` : '';
+		super(`Data validation failed for field "${name}" of ${target_info}. Encountered data of type "${type}" while expecting "${expected_desc}".${upstream_error_description}`);
 		this.data = data;
 	}
 }
 
+export class Data_Coercion_Failed extends Error {
+	constructor(data) {
+		const { value, target, expected_description, coercion_function, name, upstream_error } = data;
+		const type = value === null ? 'null' : typeof value;
+		const target_info = target ? inspect(target) : 'unknown target';
+		const expected_desc = expected_description ?? `data that would be coerced using ${coercion_function}`;
+		const upstream_error_description = upstream_error ? ` Upstream error was: ${upstream_error}` : '';
+		super(`Data coercion failed for field "${name}" of ${target_info}. Encountered data of type "${type}" while expecting "${expected_desc}".${upstream_error_description}`);
+		this.data = data;
+	}
+}
 // § GROUP: Resolving errors
 
 export class Item_Unresolvable extends Error {