Template literal validation (#10492)

* add template literal validation

* avoid null/undefined error when validating

* simplify validation logic and fix tests

Co-authored-by: Michael J. Currie <michaeljcurrie136@gmail.com>

packages/babel-types/src/definitions/es2015.js

@@ -574,6 +574,16 @@ defineType("TemplateLiteral", {
       validate: chain(
         assertValueType("array"),
         assertEach(assertNodeType("Expression")),
+        function(node, key, val) {
+          if (node.quasis.length !== val.length + 1) {
+            throw new TypeError(
+              `Number of ${
+                node.type
+              } quasis should be exactly one more than the number of expressions.\nExpected ${val.length +
+                1} quasis but got ${node.quasis.length}`,
+            );
+          }
+        },
       ),
     },
   },

packages/babel-types/test/builders/es2015/__snapshots__/templateElement.js.snap

@@ -35,3 +35,61 @@ exports[`builders es2015 templateElement should validate 5`] = `
 "Property value of TemplateElement expected to have the following:
 Property raw expected type of string but got undefined"
 `;
+
+exports[`builders es2015 templateLiteral should validate 1`] = `
+Object {
+  "expressions": Array [],
+  "quasis": Array [
+    Object {
+      "tail": false,
+      "type": "TemplateElement",
+      "value": Object {
+        "raw": "foo",
+      },
+    },
+  ],
+  "type": "TemplateLiteral",
+}
+`;
+
+exports[`builders es2015 templateLiteral should validate 2`] = `
+Object {
+  "expressions": Array [
+    Object {
+      "type": "StringLiteral",
+      "value": "baz",
+    },
+  ],
+  "quasis": Array [
+    Object {
+      "tail": false,
+      "type": "TemplateElement",
+      "value": Object {
+        "raw": "foo",
+      },
+    },
+    Object {
+      "tail": false,
+      "type": "TemplateElement",
+      "value": Object {
+        "raw": "bar",
+      },
+    },
+  ],
+  "type": "TemplateLiteral",
+}
+`;
+
+exports[`builders es2015 templateLiteral should validate 3`] = `
+"Number of TemplateLiteral quasis should be exactly one more than the number of expressions.
+Expected 3 quasis but got 2"
+`;
+
+exports[`builders es2015 templateLiteral should validate 4`] = `
+"Number of TemplateLiteral quasis should be exactly one more than the number of expressions.
+Expected 1 quasis but got 2"
+`;
+
+exports[`builders es2015 templateLiteral should validate 5`] = `"Property quasis expected type of array but got object"`;
+
+exports[`builders es2015 templateLiteral should validate 6`] = `"Property expressions expected type of array but got null"`;

packages/babel-types/test/builders/es2015/templateElement.js

@@ -21,5 +21,34 @@ describe("builders", function() {
         expect(() => t.templateElement("foo")).toThrowErrorMatchingSnapshot();
       });
     });
+    describe("templateLiteral", function() {
+      it("should validate", function() {
+        const foo = t.templateElement({ raw: "foo" });
+        const bar = t.templateElement({ raw: "bar" });
+
+        const baz = t.stringLiteral("baz");
+        const qux = t.stringLiteral("qux");
+
+        expect(t.templateLiteral([foo], [])).toMatchSnapshot();
+
+        expect(t.templateLiteral([foo, bar], [baz])).toMatchSnapshot();
+
+        expect(() =>
+          t.templateLiteral([foo, bar], [baz, qux]),
+        ).toThrowErrorMatchingSnapshot();
+
+        expect(() =>
+          t.templateLiteral([foo, bar], []),
+        ).toThrowErrorMatchingSnapshot();
+
+        expect(() =>
+          t.templateLiteral({}, [baz]),
+        ).toThrowErrorMatchingSnapshot();
+
+        expect(() =>
+          t.templateLiteral([foo, bar]),
+        ).toThrowErrorMatchingSnapshot();
+      });
+    });
   });
 });