fix: improve error message for falsy parsed JS AST (#19458)

JoshuaKGoldberg · nzakas · web-flow · commit 49e624f4a02e · 2025-02-28T12:15:11.000-05:00
* fix: improve error message for falsy parsed JS AST

* Update lib/languages/js/source-code/source-code.js

Co-authored-by: Nicholas C. Zakas &lt;nicholas@humanwhocodes.com&gt;

* Update tests

* use TypeError, not Error

---------

Co-authored-by: Nicholas C. Zakas &lt;nicholas@humanwhocodes.com&gt;
diff --git a/lib/languages/js/source-code/source-code.js b/lib/languages/js/source-code/source-code.js
@@ -58,20 +58,24 @@ const CODE_PATH_EVENTS = [
  * @private
  */
 function validate(ast) {
+    if (!ast) {
+        throw new TypeError(`Unexpected empty AST. (${ast})`);
+    }
+
     if (!ast.tokens) {
-        throw new Error("AST is missing the tokens array.");
+        throw new TypeError("AST is missing the tokens array.");
     }
 
     if (!ast.comments) {
-        throw new Error("AST is missing the comments array.");
+        throw new TypeError("AST is missing the comments array.");
     }
 
     if (!ast.loc) {
-        throw new Error("AST is missing location information.");
+        throw new TypeError("AST is missing location information.");
     }
 
     if (!ast.range) {
-        throw new Error("AST is missing range information");
+        throw new TypeError("AST is missing range information");
     }
 }
 
@@ -204,16 +208,16 @@ function isSpaceBetween(sourceCode, first, second, checkInsideOfJSXText) {
         if (
             currentToken.range[1] !== nextToken.range[0] ||
 
-                /*
-                 * For backward compatibility, check spaces in JSXText.
-                 * https://github.com/eslint/eslint/issues/12614
-                 */
-                (
-                    checkInsideOfJSXText &&
-                    nextToken !== finalToken &&
-                    nextToken.type === "JSXText" &&
-                    /\s/u.test(nextToken.value)
-                )
+            /*
+             * For backward compatibility, check spaces in JSXText.
+             * https://github.com/eslint/eslint/issues/12614
+             */
+            (
+                checkInsideOfJSXText &&
+                nextToken !== finalToken &&
+                nextToken.type === "JSXText" &&
+                /\s/u.test(nextToken.value)
+            )
         ) {
             return true;
         }
diff --git a/tests/lib/languages/js/source-code/source-code.js b/tests/lib/languages/js/source-code/source-code.js
@@ -90,6 +90,33 @@ describe("SourceCode", () => {
             assert.strictEqual(sourceCode.lines[1], "bar;");
         });
 
+        it("should throw an error when called with a false AST", () => {
+
+            assert.throws(
+                () => new SourceCode("foo;", false),
+                /Unexpected empty AST\. \(false\)/u
+            );
+
+        });
+
+        it("should throw an error when called with a null AST", () => {
+
+            assert.throws(
+                () => new SourceCode("foo;", null),
+                /Unexpected empty AST\. \(null\)/u
+            );
+
+        });
+
+        it("should throw an error when called with a undefined AST", () => {
+
+            assert.throws(
+                () => new SourceCode("foo;", void 0),
+                /Unexpected empty AST\. \(undefined\)/u
+            );
+
+        });
+
         it("should throw an error when called with an AST that's missing tokens", () => {
 
             assert.throws(
