Fix serverless#4946

Use the variable syntax present in the given variable string, extracting it from the given string that may contain embedded custom variables (i.e. `${{self:var.${{self:var.foo}}.bar}}`).

Author: erikerikson

lib/classes/Variables.js

@@ -729,7 +729,15 @@ class Variables {
     if (index < 0) {
       index = this.deep.push(variable) - 1;
     }
-    return `\${deep:${index}}`;
+    let variableContainer = variable;
+    let variableString = this.cleanVariable(variableContainer);
+    while (variableString.match(this.variableSyntax)) {
+      variableContainer = variableString;
+      variableString = this.cleanVariable(variableContainer);
+    }
+    return variableContainer
+      .replace(/\s/g, '')
+      .replace(variableString, `deep:${index}`);
   }
   appendDeepVariable(variable, subProperty) {
     return `${variable.slice(0, variable.length - 1)}.${subProperty}}`;

lib/classes/Variables.test.js

@@ -586,6 +586,44 @@ describe('Variables', () => {
         return serverless.variables.populateObject(service.custom)
           .should.become(expected);
       });
+      it('should handle deep variables regardless of custom variableSyntax', () => {
+        service.provider.variableSyntax = '\\${{([ ~:a-zA-Z0-9._\\\'",\\-\\/\\(\\)]+?)}}';
+        serverless.variables.loadVariableSyntax();
+        delete service.provider.variableSyntax;
+        service.custom = {
+          my0thStage: 'DEV',
+          my1stStage: '${{self:custom.my0thStage}}',
+          my2ndStage: '${{self:custom.my1stStage}}',
+        };
+        const expected = {
+          my0thStage: 'DEV',
+          my1stStage: 'DEV',
+          my2ndStage: 'DEV',
+        };
+        return serverless.variables.populateObject(service.custom)
+          .should.become(expected);
+      });
+      it('should handle deep variables regardless of recursion into custom variableSyntax', () => {
+        service.provider.variableSyntax = '\\${{([ ~:a-zA-Z0-9._\\\'",\\-\\/\\(\\)]+?)}}';
+        serverless.variables.loadVariableSyntax();
+        delete service.provider.variableSyntax;
+        service.custom = {
+          my0thIndex: '0th',
+          my1stIndex: '1st',
+          my0thStage: 'DEV',
+          my1stStage: '${{self:custom.my${{self:custom.my0thIndex}}Stage}}',
+          my2ndStage: '${{self:custom.my${{self:custom.my1stIndex}}Stage}}',
+        };
+        const expected = {
+          my0thIndex: '0th',
+          my1stIndex: '1st',
+          my0thStage: 'DEV',
+          my1stStage: 'DEV',
+          my2ndStage: 'DEV',
+        };
+        return serverless.variables.populateObject(service.custom)
+          .should.become(expected);
+      });
       describe('file reading cases', () => {
         let tmpDirPath;
         beforeEach(() => {