refactor: move precompilation functionality into it's own file

Author: Jake Champion

src/compileApplicationToWasm.js

@@ -4,56 +4,7 @@ import { mkdir, readFile } from "node:fs/promises";
 import { isFile } from "./isFile.js";
 import { isFileOrDoesNotExist } from "./isFileOrDoesNotExist.js";
 import wizer from "@jakechampion/wizer";
-import Parser, { Query } from "tree-sitter";
-import JavaScript from "tree-sitter-javascript";
-
-function findRegexLiterals(source) {
-  const parser = new Parser();
-  parser.setLanguage(JavaScript);
-
-  const tree = parser.parse(source);
-  const query = new Query(
-    JavaScript,
-    "(regex pattern: (regex_pattern) @pattern flags: (regex_flags)? @flags)"
-  );
-  const regexLiterals = [];
-  for (const m of query.matches(tree.rootNode)) {
-    regexLiterals.push({
-      pattern: m.captures[0].node.text,
-      flags: m.captures[1]?.node.text || "",
-    });
-  }
-  return regexLiterals;
-}
-
-const PREAMBLE = `;{
-  // Precompiled regular expressions
-  const precompile = (r) => { r.exec('a'); r.exec('\\u1000'); };`;
-const POSTAMBLE = "}";
-
-// TODO: This should also detect and update sourcemaps if they are present, otherwise the sourcemaps would be incorrect.
-// 
-/// Emit a block of javascript that will pre-compile the regular expressions given. As spidermonkey
-/// will intern regular expressions, duplicating them at the top level and testing them with both
-/// an ascii and utf8 string should ensure that they won't be re-compiled when run in the fetch
-/// handler.
-function precompile(inputApplication) {
-  let lits = findRegexLiterals(inputApplication);
-
-  if (lits.length === 0) {
-    return inputApplication;
-  }
-
-  return (
-    PREAMBLE +
-    lits
-      .map((regex) => {
-        return `precompile(/${regex.pattern}/${regex.flags});`;
-      })
-      .join("\n") +
-    POSTAMBLE
-  );
-}
+import { precompile } from "./precompile.js";
 
 export async function compileApplicationToWasm(input, output, wasmEngine) {
   try {

src/precompile.js

@@ -0,0 +1,50 @@
+import Parser, { Query } from "tree-sitter";
+import JavaScript from "tree-sitter-javascript";
+
+function findRegexLiterals(source) {
+  const parser = new Parser();
+  parser.setLanguage(JavaScript);
+
+  const tree = parser.parse(source);
+  const query = new Query(
+    JavaScript,
+    "(regex pattern: (regex_pattern) @pattern flags: (regex_flags)? @flags)"
+  );
+  const regexLiterals = [];
+  for (const m of query.matches(tree.rootNode)) {
+    regexLiterals.push({
+      pattern: m.captures[0].node.text,
+      flags: m.captures[1]?.node.text || "",
+    });
+  }
+  return regexLiterals;
+}
+
+const PREAMBLE = `;{
+  // Precompiled regular expressions
+  const precompile = (r) => { r.exec('a'); r.exec('\\u1000'); };`;
+const POSTAMBLE = "}";
+
+// TODO: This should also detect and update sourcemaps if they are present, otherwise the sourcemaps would be incorrect.
+// 
+/// Emit a block of javascript that will pre-compile the regular expressions given. As spidermonkey
+/// will intern regular expressions, duplicating them at the top level and testing them with both
+/// an ascii and utf8 string should ensure that they won't be re-compiled when run in the fetch
+/// handler.
+export function precompile(inputApplication) {
+  let lits = findRegexLiterals(inputApplication);
+
+  if (lits.length === 0) {
+    return inputApplication;
+  }
+
+  return (
+    PREAMBLE +
+    lits
+      .map((regex) => {
+        return `precompile(/${regex.pattern}/${regex.flags});`;
+      })
+      .join("\n") +
+    POSTAMBLE + inputApplication
+  );
+}