Fix outstanding issues

bin/peggy-cli.js

@@ -291,7 +291,7 @@ class PeggyCLI extends Command {
         this.outputFile = this.progOptions.output;
         this.outputJS = this.progOptions.output;
 
-        if ((this.inputFiles.indexOf("-") !== -1) && this.argv.watch) {
+        if ((this.inputFiles.includes("-")) && this.argv.watch) {
           this.argv.watch = false; // Make error throw.
           this.error("Can't watch stdin");
         }
@@ -300,7 +300,7 @@ class PeggyCLI extends Command {
           if (this.inputFiles.indexOf("-") === -1) {
             let inFile = this.inputFiles[0];
             // You might just want to run a fragment grammar as-is,
-            // particularyly with a specified start rule.
+            // particularly with a specified start rule.
             const m = inFile.match(/^npm:.*\/([^/]+)$/);
             if (m) {
               inFile = m[1];
@@ -586,11 +586,7 @@ class PeggyCLI extends Command {
       const dirname = path.dirname(filename);
       const m = new Module(filename, module);
       // This is the function that will be called by `require()` in the parser.
-      m.require = (
-        // In node 12+, createRequire is documented.
-        // In node 10, createRequireFromPath is the least-undocumented approach.
-        Module.createRequire || Module.createRequireFromPath
-      )(filename);
+      m.require = Module.createRequire(filename);
       const script = new vm.Script(source, { filename });
       const exec = script.runInNewContext({
         // Anything that is normally in the global scope that we think
@@ -653,11 +649,7 @@ class PeggyCLI extends Command {
           this.std.in.resume();
           input.text = await readStream(this.std.in);
         } else if (source.startsWith("npm:")) {
-          const req = (
-            // In node 12+, createRequire is documented.
-            // In node 10, createRequireFromPath is the least-undocumented approach.
-            Module.createRequire || Module.createRequireFromPath
-          )(prevSource);
+          const req = Module.createRequire(prevSource);
           prevSource = req.resolve(source.slice(4));
           input.source = prevSource;
           input.text = await fs.promises.readFile(prevSource, "utf8");

bin/watcher.js

@@ -43,7 +43,7 @@ class Watcher extends EventEmitter {
           return;
         }
         const filename = path.join(dir, fn);
-        // Might be a different fil changing in one of the target dirs
+        // Might be a different file changing in one of the target dirs
         if (resolved.has(filename)) {
           if (!this.timeout) {
             fs.stat(filename, (er, stats) => {

docs/documentation.html

@@ -127,11 +127,16 @@ <h3 id="generating-a-parser-command-line">Command Line</h3>
   are used.</p>
 
 <p>If you specify multiple input files, they will be folded together in the
-  order specified before generating a parser.  <code>import</code> statements in
-  the top-level initializers from each of the inputs will be moved to the top of
-  the generated code, and all other top-level initializers will be inserted
-  directly after those imports, in the order of the inputs.  This approach can
-  be used to keep libraries of often-used grammar rules in separate files.</p>
+order specified before generating a parser.  If generating the "es" format,
+<code>import</code> statements in the top-level initializers from each of the
+inputs will be moved to the top of the generated code in reverse order of the
+inputs, and all other top-level initializers will be inserted directly after
+those imports, also in reverse order of the inputs.  Note that because the
+input JavaScript is parsed using a grammar very close to the ECMAscript
+grammar, if import statements are found, all comments before the first
+non-import statement will move with the import statement, which may be a
+little surprising.  This approach can be used to keep libraries of often-used
+grammar rules in separate files.</p>
 
 <p>By default, the generated parser is in the commonjs module format. You can
   override this using the <code>--format</code> option.</p>

lib/compiler/asts.js

@@ -12,13 +12,13 @@ const visitor = require("./visitor");
  * @returns {T | T[]}
  */
 function combinePossibleArrays(a, b) {
+  // First might be an array, second will not.  Either might be null.
+  if (!(a && b)) {
+    return a || b;
+  }
   const aa = Array.isArray(a) ? a : [a];
-  const bb = Array.isArray(b) ? b : [b];
-
-  // Put library code above code that uses it, so that variables
-  // will be in scope.
-  const res = bb.filter(x => x).concat(aa.filter(x => x)); // Remove nulls.
-  return res;
+  aa.push(b);
+  return aa;
 }
 
 // AST utilities.

lib/compiler/passes/generate-js.js

@@ -865,9 +865,12 @@ function generateJS(ast, options) {
               codes.push(tli);
             }
           }
-          topLevel = imps.concat(codes);
+          // Imports go at the end so that when reversed, they end up in front.
+          topLevel = codes.concat(imps);
         }
-        for (const tli of topLevel) {
+        // Put library code before code using it.
+        const reversed = [...topLevel].reverse();
+        for (const tli of reversed) {
           parts.push(ast2SourceNode(tli));
           parts.push("");
         }