fix #126; disallow top-level export

Author: mbostock

src/javascript.ts

@@ -5,8 +5,9 @@ import {findDeclarations} from "./javascript/declarations.js";
 import {findFeatures} from "./javascript/features.js";
 import {rewriteFetches} from "./javascript/fetches.js";
 import {defaultGlobals} from "./javascript/globals.js";
-import {findImports, rewriteImports} from "./javascript/imports.js";
+import {findExports, findImports, rewriteImports} from "./javascript/imports.js";
 import {findReferences} from "./javascript/references.js";
+import {syntaxError} from "./javascript/syntaxError.js";
 import {Sourcemap} from "./sourcemap.js";
 
 export interface DatabaseReference {
@@ -131,6 +132,8 @@ function parseJavaScript(input: string, options: ParseOptions): JavaScriptNode {
   if (expression?.type === "FunctionExpression" && expression.id) expression = null; // treat named function as program
   if (!expression && inline) throw new SyntaxError("invalid expression");
   const body = expression ?? (Parser.parse(input, parseOptions) as any);
+  const exports = findExports(body);
+  if (exports.length) throw syntaxError("Unexpected token 'export'", exports[0], input); // disallow exports
   const references = findReferences(body, globals, input);
   const declarations = expression ? null : findDeclarations(body, globals, input);
   const imports = findImports(body, root, sourcePath);

src/javascript/imports.ts

@@ -1,19 +1,32 @@
 import {readFileSync} from "node:fs";
 import {dirname, join, normalize} from "node:path";
-import {type Node, Parser} from "acorn";
+import {type ExportAllDeclaration, type ExportNamedDeclaration, type Node, Parser} from "acorn";
 import {simple} from "acorn-walk";
 import {type ImportReference, type JavaScriptNode, parseOptions} from "../javascript.js";
 import {getStringLiteralValue, isStringLiteral} from "./features.js";
 
+export function findExports(body: Node) {
+  const exports: (ExportAllDeclaration | ExportNamedDeclaration)[] = [];
+
+  simple(body, {
+    ExportAllDeclaration: findExport,
+    ExportNamedDeclaration: findExport
+  });
+
+  function findExport(node: ExportAllDeclaration | ExportNamedDeclaration) {
+    exports.push(node);
+  }
+
+  return exports;
+}
+
 export function findImports(body: Node, root: string, sourcePath: string) {
   const imports: ImportReference[] = [];
   const paths = new Set<string>();
 
   simple(body, {
     ImportDeclaration: findImport,
-    ImportExpression: findImport,
-    ExportAllDeclaration: findImport,
-    ExportNamedDeclaration: findImport
+    ImportExpression: findImport
   });
 
   function findImport(node) {

test/input/export.js

@@ -0,0 +1 @@
+export const foo = 42;

test/output/export.js

@@ -0,0 +1 @@
+define({id: "0", body: () => { throw new SyntaxError("Unexpected token 'export' (1:0)"); }});