feat: custom step for js translator

src/lib/translators/js.ts

@@ -124,6 +124,19 @@ export class JavaScriptTranslator extends BaseTranslator {
       return data.map(addTextColumnToRow);
     };
   }
+
+  /**
+   * Transform a "custom" step into corresponding function
+   *
+   * The "query" parameter of the custom step should be a javascript function, of which the first parameter will be
+   * the data table, and the second an object of all available domains.
+   */
+  custom(step: Readonly<S.CustomStep>) {
+    const func = Function('"use strict";return (' + step.query + ')')();
+    return function(data: Readonly<DataTable>, dataDomains: Readonly<DataDomains>) {
+      return func(data, dataDomains);
+    };
+  }
 }
 
 /**

tests/unit/js.spec.ts

@@ -254,4 +254,23 @@ describe('Pipeline to js function translator', () => {
       ]);
     });
   });
+
+  describe('custom step', () => {
+    it('should apply the custom function to data', () => {
+      const addPlipPloupAndDoubleValue = jsTranslator.custom({
+        name: 'custom',
+        query: `function transformData(data) {
+          return data.map(d => ({
+            ...d,
+            value: d.value * 2,
+            plip: "ploup"
+          }));
+        }`,
+      });
+      expect(addPlipPloupAndDoubleValue(SAMPLE_DATA.domainA, {})).toEqual([
+        { label: 'A', value: 2, plip: 'ploup' },
+        { label: 'B', value: 4, plip: 'ploup' },
+      ]);
+    });
+  });
 });