Attempt at validation codegen

.gitignore

@@ -130,3 +130,4 @@ dist
 .pnp.*
 
 package-lock.json
+.vscode

index.js

@@ -134,6 +134,7 @@ class Struct extends ResolvedType {
 
     this.fields = []
     this.fieldsByName = new Map()
+    this.requiredFields = []
 
     this.optionals = []
     this.flagsPosition = -1
@@ -184,6 +185,8 @@ class Struct extends ResolvedType {
         if (this.flagsPosition === -1) {
           this.flagsPosition = i
         }
+      } else {
+        this.requiredFields.push(field)
       }
     }
   }
@@ -290,19 +293,19 @@ module.exports = class Hyperschema {
     return json
   }
 
-  toCode () {
-    return generateCode(this)
+  toCode (opts = {}) {
+    return generateCode(this, opts)
   }
 
-  static toDisk (hyperschema, dir) {
+  static toDisk (hyperschema, dir, opts = {}) {
     if (!dir) dir = hyperschema.dir
     fs.mkdirSync(dir, { recursive: true })
 
     const jsonPath = p.join(p.resolve(dir), JSON_FILE_NAME)
     const codePath = p.join(p.resolve(dir), CODE_FILE_NAME)
 
     fs.writeFileSync(jsonPath, JSON.stringify(hyperschema.toJSON(), null, 2), { encoding: 'utf-8' })
-    fs.writeFileSync(codePath, hyperschema.toCode(), { encoding: 'utf-8' })
+    fs.writeFileSync(codePath, hyperschema.toCode(opts), { encoding: 'utf-8' })
   }
 
   static from (json) {

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, opts = {}) {
   const structs = []
   const structsByName = new Map()
 
@@ -108,6 +108,9 @@ module.exports = function generateSchema (hyperschema) {
     str += `// ${struct.fqn}\n`
     str += `const ${id} = {\n`
     str += '  preencode (state, m) {\n'
+    if (opts.debug) {
+      str += generateValidation(struct)
+    }
     str += `${preencode}\n`
     str += '  },\n'
     str += '  encode (state, m) {\n'
@@ -119,6 +122,18 @@ module.exports = function generateSchema (hyperschema) {
     str += '}\n'
     return str
 
+    function generateValidation (struct) {
+      if (!struct.requiredFields.length) return ''
+
+      let str = ''
+      str += '    const errors = []\n'
+      for (const field of struct.requiredFields) {
+        str += `    if (${gen('m', field.name)} === undefined || ${gen('m', field.name)} === null) errors.push('${field.name}')\n`
+      }
+      str += `    if(errors.length) throw new Error(\`${struct.fqn}[\${errors.join(',')}] \${errors.length>1?'are':'is'} required\`)\n\n`
+      return str
+    }
+
     function generateEncode (struct, { preencode = false } = {}) {
       const fn = preencode ? 'preencode' : 'encode'
       let str = ''