add JS AST querying with XPath

website/package.json

@@ -54,6 +54,7 @@
     "acorn-to-esprima": "^1.0.2",
     "astexplorer-refmt": "^1.0.1",
     "astexplorer-syn": "^0.15.30",
+    "astq": "^2.6.2",
     "babel-core": "^6.24.0",
     "babel-eslint": "^7.2.3",
     "babel-eslint8": "file:packages/babel-eslint8",

website/src/parsers/js/transformers/astq/codeExample.txt

@@ -0,0 +1 @@
+// VariableDeclaration [@kind == 'const']

website/src/parsers/js/transformers/astq/index.js

@@ -0,0 +1,43 @@
+import pkg from 'astq/package.json';
+
+const ID = 'astq';
+const name = 'ASTQ';
+
+export default {
+  id: ID,
+  displayName: name,
+  version: pkg.version,
+  homepage: pkg.homepage,
+
+  defaultParserID: 'esprima',
+
+  loadTransformer (callback) {
+    require(['esprima', 'astq'], (esprima, astq) =>
+      callback({ esprima, astq }));
+  },
+
+  transform ({ esprima, astq }, xPathQuery, code) {
+    const ASTQ = new astq();
+    ASTQ.adapter('mozast');
+
+    let results = {
+      matches: 0,
+      nodes: [],
+    };
+    if (!xPathQuery || xPathQuery === '') {
+      return JSON.stringify(results, null, 2);
+    }
+
+    try {
+      const ast = esprima.parseScript(code);
+      const nodes = ASTQ.query(ast, xPathQuery);
+      results = {
+        matches: nodes.length,
+        nodes,
+      };
+      return JSON.stringify(results, null, 2);
+    } catch ({ message }) {
+      return message;
+    }
+  },
+};