feat(core): add has output visitor to check wether the template has any valid output

Author: oscar60310

packages/core/src/lib/template-engine/compiler.ts

@@ -26,5 +26,6 @@ export interface CompileResult {
 export interface Compiler {
   name: string;
   compile(template: string): CompileResult;
+  execute<T extends object>(template: string, data: T): Promise<any>;
   render<T extends object>(templateName: string, data: T): Promise<string>;
 }

packages/core/src/lib/template-engine/nunjucksCompiler.ts

@@ -14,6 +14,7 @@ import {
   ErrorsVisitor,
   FiltersVisitor,
   BuilderValueVisitor,
+  HasOutputValueVisitor,
 } from './visitors';
 import { inject, injectable, multiInject, optional } from 'inversify';
 import { TYPES } from '@vulcan/core/containers';
@@ -53,6 +54,16 @@ export class NunjucksCompiler implements Compiler {
     return { ast: preProcessedAst, metadata };
   }
 
+  public async execute<T extends object>(
+    templateName: string,
+    data: T
+  ): Promise<any> {
+    const template = this.env.getTemplate(templateName, true);
+
+    // const query = await this.render(template, data);
+    // console.log(data);
+  }
+
   public async render<T extends object>(
     templateName: string,
     data: T
@@ -93,10 +104,18 @@ export class NunjucksCompiler implements Compiler {
     const errors = new ErrorsVisitor();
     const filters = new FiltersVisitor({ env: this.env });
     const builderValueVisitor = new BuilderValueVisitor();
-    walkAst(ast, [parameters, errors, filters, builderValueVisitor]);
+    const hasOutputVisitor = new HasOutputValueVisitor();
+    walkAst(ast, [
+      parameters,
+      errors,
+      filters,
+      builderValueVisitor,
+      hasOutputVisitor,
+    ]);
     return {
       parameters: parameters.getParameters(),
       errors: errors.getErrors(),
+      hasOutput: hasOutputVisitor.getHasOutput(),
     };
   }
 

packages/core/src/lib/template-engine/visitors/hasOutputVisitor.ts

@@ -0,0 +1,28 @@
+import { Visitor } from './visitor';
+import * as nunjucks from 'nunjucks';
+
+// Check whether the given tree has any output.
+
+export class HasOutputValueVisitor implements Visitor {
+  private hasOutput = false;
+
+  public visit(node: nunjucks.nodes.Node) {
+    // If there is an output, we can stop visiting the tree.
+    if (this.hasOutput) return;
+
+    if (
+      node instanceof nunjucks.nodes.TemplateData &&
+      this.trimOutput(node.value).length > 0
+    ) {
+      this.hasOutput = true;
+    }
+  }
+
+  public getHasOutput(): boolean {
+    return this.hasOutput;
+  }
+
+  private trimOutput(output: string) {
+    return output.replace(/[\r\n ]/g, '');
+  }
+}

packages/core/src/lib/template-engine/visitors/index.ts

@@ -4,3 +4,4 @@ export * from './errorsVisitor';
 export * from './filtersVisitor';
 export * from './astWalker';
 export * from './builderValueVisitor';
+export * from './hasOutputVisitor';

packages/core/test/template-engine/visitors/hasOutput.spec.ts

@@ -0,0 +1,37 @@
+import { HasOutputValueVisitor, walkAst } from '@vulcan/core/template-engine';
+import * as nunjucks from 'nunjucks';
+
+const test = (template: string, expected: boolean) => {
+  // Arrange
+  const ast = nunjucks.parser.parse(template, [], {});
+  const visitor = new HasOutputValueVisitor();
+  // Act
+  walkAst(ast, [visitor]);
+  const hasOutput = visitor.getHasOutput();
+  // Assert
+  expect(hasOutput).toBe(expected);
+};
+
+it('Should return false if there is no valid output', async () => {
+  test(
+    `
+    {{ params.a }}
+    {% if params.b %}
+      {{ params.c }}
+    {% endif %}
+    `,
+    false
+  );
+});
+
+it('Should return true if there are simple outputs', async () => {
+  test(`select * from users;`, true);
+});
+
+it('Should return true if there are outputs inside statements', async () => {
+  test(`{% if 1 == 2 %}select * from users;{% endif %}`, true);
+});
+
+it('(Known issue)Should return false if the output is looked from variables', async () => {
+  test(`{% set query = "select * from users;" %}{{ query }}`, false);
+});

types/nunjucks.d.ts

@@ -342,6 +342,8 @@ declare module 'nunjucks' {
       body: Node | null;
       targets: Node[];
     }
+
+    class TemplateData extends Literal {}
   }
 
   namespace lexer {