DependencyProcessor empty string expr. setData undefined should becom…

…e null.

src/DependencyFinder.ts

@@ -45,9 +45,11 @@ export default class DependencyFinder {
      */
     constructor(program: string | ExprNode) {
         if (typeof program === 'string') {
-            // Handle the case where program is a string
-            this.compiledExpression = jsonata(program);
-            this.ast = this.compiledExpression.ast();
+            if(program !== "") {
+                // Handle the case where program is a string
+                this.compiledExpression = jsonata(program);
+                this.ast = this.compiledExpression.ast();
+            }
         } else {
             this.ast = program;
         }
@@ -74,6 +76,9 @@ export default class DependencyFinder {
         Walk the AST of the JSONata program
      */
     findDependencies(node:GeneratedExprNode = this.ast):string[][] {
+        if(!this.ast){
+            return [];
+        }
         if (this.currentSteps.length === 0) {
             this.currentSteps.push([]); //initialize a container for steps
         }

src/TemplateProcessor.ts

@@ -919,7 +919,7 @@ export default class TemplateProcessor {
     }
 
 
-    async setData(jsonPtr, data, op="set") {
+    async setData(jsonPtr, data=null, op="set") {
         this.isEnabled("debug") && this.logger.debug(`setData on ${jsonPtr} for TemplateProcessor uid=${this.uniqueId}`)
         //get all the jsonPtrs we need to update, including this one, to percolate the change
         const sortedJsonPtrs = [...this.from(jsonPtr)]; //defensive copy

src/test/DependencyFinder.test.js

@@ -764,6 +764,20 @@ test("homeworldURLs.$fetch($).json()", () => {
     expect(deps).toEqual([["homeworldURLs"]]);
 });
 
+test("function($planet){$planet.residents.($fetch($).json())}", () => {
+    const program = "function($planet){$planet.residents.($fetch($).json())}";
+    const df = new DependencyFinder(program);
+    const deps = df.findDependencies();
+    expect(deps).toEqual([]);
+});
+
+test("empty string", () => {
+    const program = "";
+    const df = new DependencyFinder(program);
+    const deps = df.findDependencies();
+    expect(deps).toEqual([]);
+});
+