Refactor decode and fix bools (#10)

* always define all props and do it in one go

* fix required bools

index.js

@@ -166,6 +166,13 @@ class Struct extends ResolvedType {
 
     for (let i = 0; i < description.fields.length; i++) {
       const fieldDescription = description.fields[i]
+
+      // bools can only be set in the flag, so auto downgrade the from required
+      // TODO: if we add semantic meaning to required, ie "user MUST set this", we should
+      // add an additional state for this
+      if (fieldDescription.required && fieldDescription.type === 'bool') {
+        fieldDescription.required = false
+      }
       const flag = !fieldDescription.required ? 2 ** this.optionals.length : 0
       const field = new StructField(hyperschema, this, i, flag, fieldDescription)
 

lib/codegen.js

@@ -174,42 +174,57 @@ module.exports = function generateSchema (hyperschema) {
     function generateDecode (struct) {
       let str = ''
 
-      str += '    const res = {}\n'
+      const pre = new Map()
       for (let i = 0; i < struct.fields.length; i++) {
         const field = struct.fields[i]
-        str += `    ${vPrefix(field.version)}${gen('res', field.name)} = ${field.type.default}\n`
+        if (!field.required || field.type.bool || i === struct.flagsPosition) break
+        pre.set(field, 'r' + i)
+        str += `    const r${i} = ${getFieldEncoder(field)}.decode(state)\n`
+      }
+
+      if (pre.size === struct.flagsPosition) {
+        str += '    const flags = state.start < state.end ? c.uint.decode(state) : 0\n\n'
+      } else if (pre.size) {
+        str += '\n'
       }
-      str += '\n'
+
+      str += '    return {\n'
 
       for (let i = 0; i < struct.fields.length; i++) {
         const field = struct.fields[i]
-        let decodeStr = ''
-        if (field.type.bool) {
-          decodeStr = `${gen('res', field.name)} = true`
-        } else {
-          decodeStr = `${gen('res', field.name)} = ${getFieldEncoder(field)}.decode(state)`
-        }
+        const end = i < struct.fields.length - 1 ? ',\n' : '\n'
+        const flag = vInlinePrefix(field.version, `(flags & ${field.flag}) !== 0`)
+        const prop = gen.property(field.name)
 
-        if (i === struct.flagsPosition) {
-          if (i !== 0) str += '\n'
-          str += '    const flags = state.start < state.end ? c.uint.decode(state) : 0\n'
+        if (pre.has(field)) {
+          str += `      ${prop}: ${pre.get(field)}${end}`
+          continue
+        }
+        if (field.type.bool) {
+          str += `      ${prop}: ${flag}${end}`
+          continue
         }
-
         if (field.required) {
-          str += `    ${decodeStr}\n`
-        } else {
-          str += `    ${vPrefix(field.version, `(flags & ${field.flag}) !== 0`)} ${decodeStr}\n`
+          str += `      ${prop}: ${getFieldEncoder(field)}.decode(state)${end}`
+          continue
         }
+
+        str += `      ${prop}: ${flag} ? ${getFieldEncoder(field)}.decode(state) : ${field.type.default}${end}`
       }
 
-      if (struct.fields.length !== 0) str += '\n'
-      str += '    return res'
+      str += '    }'
+
       return str
     }
 
     function vPrefix (v, condition) {
       if (v === 1) return condition ? `if (${condition})` : ''
-      return condition ? `if ((version >= ${v}) && ${condition})` : `if (version >= ${v}) `
+      return condition ? `if (version >= ${v} && ${condition})` : `if (version >= ${v}) `
+    }
+
+    function vInlinePrefix (v, condition) {
+      if (v === 1) return condition || ''
+      return condition ? `(version >= ${v} && ${condition})` : `version >= ${v}`
     }
 
     function getFieldEncoder (field) {