feat(condition-checker): add #evaluate

Author: Niklas Kiefer

packages/form-js-viewer/src/core/ConditionChecker.js

@@ -1,4 +1,4 @@
-import { unaryTest } from 'feelin';
+import { unaryTest, evaluate } from 'feelin';
 import { isString } from 'min-dash';
 
 /**
@@ -81,6 +81,33 @@ export class ConditionChecker {
     return result === true;
   }
 
+  /**
+   * Evaluate an expression.
+   *
+   * @param {string} expression
+   * @param {import('../types').Data} [data]
+   *
+   * @returns {any}
+   */
+  evaluate(expression, data = {}) {
+    if (!expression) {
+      return null;
+    }
+
+    if (!isString(expression) || !expression.startsWith('=')) {
+      return null;
+    }
+
+    try {
+      const result = evaluate(expression.slice(1), data);
+
+      return result;
+    } catch (error) {
+      this._eventBus.fire('error', { error });
+      return null;
+    }
+  }
+
   _getConditions() {
     const formFields = this._formFieldRegistry.getAll();
 

packages/form-js-viewer/test/spec/core/ConditionChecker.spec.js

@@ -122,6 +122,87 @@ describe('ConditionChecker', function() {
   });
 
 
+  describe('#evaluate', function() {
+
+    it('should return null if there is no expression', function() {
+
+      // when
+      const result = conditionChecker.evaluate(null, null, false);
+
+      // then
+      expect(result).to.be.null;
+    });
+
+
+    it('should return null for non-string expression', function() {
+
+      // given
+      const expression = 1;
+
+      // when
+      const result = conditionChecker.evaluate(expression);
+
+      // then
+      expect(result).to.be.null;
+    });
+
+
+    it('should return null if expression does not start with =', function() {
+
+      // given
+      const expression = 'foo';
+
+      // when
+      const result = conditionChecker.evaluate(expression);
+
+      // then
+      expect(result).to.be.null;
+    });
+
+
+    it('should return null and report error if condition has syntax error', function() {
+
+      // given
+      const expression = '=foo-';
+
+      // when
+      const result = conditionChecker.evaluate(expression);
+
+      // then
+      expect(result).to.be.null;
+      expect(fireSpy).to.have.been.calledWith('error');
+      expect(fireSpy.args[0][1].error).to.be.instanceof(Error);
+    });
+
+
+    it('should return expression result', function() {
+
+      // given
+      const expression = '=2 + 2 + 5';
+
+      // when
+      const result = conditionChecker.evaluate(expression);
+
+      // then
+      expect(result).to.equal(9);
+    });
+
+
+    it('should return expression result (with data)', function() {
+
+      // given
+      const expression = '=2 + 2 + five';
+
+      // when
+      const result = conditionChecker.evaluate(expression, { five: 5 });
+
+      // then
+      expect(result).to.equal(9);
+    });
+
+  });
+
+
   describe('#applyConditions', function() {
 
     it('should filter out properties for which condition is not met', function() {