✨ Recompute field values on the fly

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 1.3.21 (WIP)
+
+* Add `Schema#addComputedField()` method
+
 ## 1.3.20 (2023-11-04)
 
 * Make `Base#callOrNext(name, args, next)` handle methods without callbacks
@@ -11,7 +15,6 @@
 * Make the `Decimal` classes globally available
 * Allow passing a custom context to `PathEvaluator#getValue(context)`
 * Fix `TaskService#initSchedules()` attempting to recreate already existing system schedules
-* Add `Schema#addComputedField()` method
 
 ## 1.3.19 (2023-10-18)
 

lib/app/helper_model/document.js

@@ -131,6 +131,25 @@ Document.setStatic(function setMethod(key, method, on_server) {
 	return Blast.Collection.Function.setMethod(this, key, method);
 });
 
+/**
+ * Set a getter for this computed field
+ *
+ * @author   Jelle De Loecker <jelle@elevenways.be>
+ * @since    1.3.21
+ * @version  1.3.21
+ *
+ * @param    {String}     name       Name of the property
+ * @param    {Boolean}    on_server  Also set on the server implementation
+ */
+Document.setStatic(function setComputedFieldGetter(name, on_server) {
+	this.setProperty(name, function getComputedFieldValue() {
+		this.recomputeFieldIfNecessary(name);
+		return this.$main[name];
+	}, function setComputedFieldValue(value) {
+		console.error('Can not set computed field "' + name + '" to', value);
+	}, on_server);
+});
+
 /**
  * Set a getter for this field
  *
@@ -858,6 +877,97 @@ Document.setMethod(function setValues(values) {
 
 });
 
+/**
+ * Recompute the given field if required
+ *
+ * @author   Jelle De Loecker <jelle@elevenways.be>
+ * @since    1.3.21
+ * @version  1.3.21
+ *
+ * @return   {Pledge|undefined}
+ */
+Document.setMethod(function recomputeFieldIfNecessary(name, force = false) {
+
+	const field = this.$model.schema.computed_fields[name];
+
+	if (!field) {
+		return;
+	}
+
+	let options = field.options,
+	    required_field_count = options.required_fields?.length || 0,
+	    optional_field_count = options.optional_fields?.length || 0;
+
+	if (!force && this.$main[name] == null) {
+		// If the value is null, it hasn't been computed yet
+		// and we need to compute it
+		force = true;
+	}
+
+	if (!force) {
+		let has_changed = false;
+
+		if (required_field_count) {
+			for (let required_field of options.required_fields) {
+				if (this.hasChanged(required_field)) {
+					has_changed = true;
+					break;
+				}
+			}
+		}
+
+		if (!has_changed && optional_field_count) {
+			for (let optional_field of options.optional_fields) {
+				if (this.hasChanged(optional_field)) {
+					has_changed = true;
+					break;
+				}
+			}
+		}
+
+		if (!has_changed) {
+			return;
+		}
+	}
+
+	// Make sure the required fields are set
+	if (required_field_count) {
+		let has_value = true;
+
+		for (let required_field of options.required_fields) {
+			if (this[required_field] == null) {
+				has_value = false;
+				break;
+			}
+		}
+
+		if (!has_value) {
+			// If not all required field values are set,
+			// the result will also be undefined
+			this.$main[name] = undefined;
+			return;
+		}
+	}
+
+	let compute_method = options.compute_method;
+
+	if (typeof compute_method == 'string') {
+		compute_method = this[compute_method];
+	}
+
+	let result = compute_method.call(this);
+
+	if (Pledge.isThenable(result)) {
+		result.then(value => {
+			this.$main[name] = value;
+		});
+
+		return result;
+	} else {
+		this.$main[name] = result;
+	}
+});
+
 /**
  * Recompute values of computed fields.
  * This might be async. If it is, a pledge will be returned.

lib/class/document.js

@@ -178,6 +178,26 @@ Document.setStatic(function unDry(obj, cloned) {
 	return result;
 });
 
+/**
+ * Set the getter for this computed field
+ *
+ * @author   Jelle De Loecker <jelle@elevenways.be>
+ * @since    1.3.21
+ * @version  1.3.21
+ *
+ * @param    {String}     name     Name of the property
+ * @param    {Function}   getter   Optional getter function
+ * @param    {Function}   setter   Optional setter function
+ */
+Document.setStatic(function setComputedFieldGetter(name) {
+	this.setProperty(name, function getComputedFieldValue() {
+		this.recomputeFieldIfNecessary(name);
+		return this.$main[name];
+	}, function setComputedFieldValue(value) {
+		console.error('Can not set computed field "' + name + '" to', value);
+	});
+});
+
 /**
  * Set the getter for this field
  *

lib/class/model.js

@@ -383,12 +383,12 @@ Model.setStatic(function addComputedField(name, type, options) {
 
 	if (is_new) {
 		// Add it to the Document class
-		this.Document.setFieldGetter(name);
+		this.Document.setComputedFieldGetter(name);
 
 		// False means it should not be set on the server implementation
 		// (because that's where it's coming from)
 		// Yes, this also sets private fields on the server-side client document.
-		this.ClientDocument.setFieldGetter(name, null, null, false);
+		this.ClientDocument.setComputedFieldGetter(name, null, null, false);
 	}
 
 	return field;

package.json

@@ -1,7 +1,7 @@
 {
 	"name": "alchemymvc",
 	"description": "MVC framework for Node.js",
-	"version": "1.3.20",
+	"version": "1.3.21-alpha",
 	"author": "Jelle De Loecker <jelle@elevenways.be>",
 	"keywords": [
 		"alchemy",

test/03-model.js

@@ -700,6 +700,7 @@ describe('Model', function() {
 			const ComputedPerson = Function.inherits('Alchemy.Model', 'ComputedPerson');
 
 			ComputedPerson.constitute(function addFields() {
+				this.addField('number', 'Integer');
 				this.addField('firstname', 'String');
 				this.addField('lastname',  'String');
 				this.addComputedField('fullname', 'String', {
@@ -726,6 +727,7 @@ describe('Model', function() {
 
 			let doc = Model.get('ComputedPerson').createDocument();
 
+			doc.number = 1;
 			doc.firstname = 'Jelle';
 			doc.lastname = 'De Loecker';
 
@@ -738,6 +740,38 @@ describe('Model', function() {
 
 			assert.strictEqual(doc.fullname, 'Jellie De Loecker');
 		});
+
+		it('should update synchronous field values on get', async function() {
+
+			let doc = Model.get('ComputedPerson').createDocument();
+
+			doc.number = 2;
+			doc.firstname = 'Jelle';
+			doc.lastname = 'De Loecker';
+
+			assert.strictEqual(doc.fullname, 'Jelle De Loecker');
+
+			doc.firstname = 'Jellie';
+
+			assert.strictEqual(doc.fullname, 'Jellie De Loecker');
+
+			await doc.save();
+			assert.strictEqual(doc.fullname, 'Jellie De Loecker');
+			assert.strictEqual(doc.$main.fullname, 'Jellie De Loecker');
+
+			doc.$main.fullname = null;
+			assert.strictEqual(doc.fullname, 'Jellie De Loecker');
+			assert.strictEqual(doc.$main.fullname, 'Jellie De Loecker');
+
+			doc.$main.fullname = null;
+			await doc.save();
+			assert.strictEqual(doc.fullname, 'Jellie De Loecker');
+			assert.strictEqual(doc.$main.fullname, 'Jellie De Loecker');
+
+			doc = await Model.get('ComputedPerson').findByValues({number: 2});
+			assert.strictEqual(doc.fullname, 'Jellie De Loecker');
+			assert.strictEqual(doc.$main.fullname, 'Jellie De Loecker');
+		});
 	});
 
 	/**