support esm generation

index.js

@@ -344,8 +344,8 @@ module.exports = class Hyperschema {
     return json
   }
 
-  toCode () {
-    return generateCode(this)
+  toCode (opts) {
+    return generateCode(this, opts)
   }
 
   static toDisk (hyperschema, dir) {

lib/codegen.js

@@ -1,7 +1,7 @@
 const gen = require('generate-object-property')
 const s = require('generate-string')
 
-module.exports = function generateSchema (hyperschema) {
+module.exports = function generateSchema (hyperschema, { esm = false } = {}) {
   const structs = []
   const structsByName = new Map()
 
@@ -30,7 +30,13 @@ module.exports = function generateSchema (hyperschema) {
   str += '/* eslint-disable quotes */\n'
   str += '\n'
   str += `const VERSION = ${hyperschema.version}\n`
-  str += 'const { c } = require(\'hyperschema/runtime\')\n'
+
+  if (esm) {
+    str += 'import { c } from \'hyperschema/runtime\')\n'
+  } else {
+    str += 'const { c } = require(\'hyperschema/runtime\')\n'
+  }
+
   str += '\n'
   str += '// eslint-disable-next-line no-unused-vars\n'
   str += 'let version = VERSION\n'
@@ -102,7 +108,14 @@ module.exports = function generateSchema (hyperschema) {
   str += '  }\n'
   str += '}\n'
   str += '\n'
-  str += 'module.exports = { resolveStruct: getStruct, getStruct, getEnum, getEncoding, encode, decode, setVersion, version }\n'
+  str += 'const resolveStruct = getStruct // compat\n'
+  str += '\n'
+
+  if (esm) {
+    str += 'export { resolveStruct, getStruct, getEnum, getEncoding, encode, decode, setVersion, version }\n'
+  } else {
+    str += 'module.exports = { resolveStruct, getStruct, getEnum, getEncoding, encode, decode, setVersion, version }\n'
+  }
 
   return str
 

package.json

@@ -8,6 +8,13 @@
     "index.js",
     "runtime.js"
   ],
+  "exports": {
+    ".": "./index.js",
+    "./runtime": {
+      "import": "./runtime.mjs",
+      "default": "./runtime.cjs"
+    }
+  },
   "scripts": {
     "test": "standard && brittle test/index.js",
     "test:bare": "standard && bare test/index.js"

runtime.mjs

@@ -0,0 +1,3 @@
+import compact from 'compact-encoding'
+
+export const c = compact

test/helpers/index.js

@@ -39,7 +39,7 @@ async function makeDir (t) {
   // Copy the runtime into the tmp dir so that we don't need to override it in the codegen
   const runtimePath = p.join(dir, 'node_modules', 'hyperschema', 'runtime.js')
   await fs.promises.mkdir(p.dirname(runtimePath), { recursive: true })
-  await fs.promises.copyFile(p.resolve(dir, '../../../runtime.js'), runtimePath)
+  await fs.promises.copyFile(p.resolve(dir, '../../../runtime.cjs'), runtimePath)
   return dir
 }