wip: add comments

Author: edison1105

packages/compiler-vapor/src/generate.ts

@@ -38,6 +38,7 @@ export class CodegenContext {
   currentRenderEffect: IREffect | undefined = undefined
   renderEffectSeemNames: Record<string, number> = Object.create(null)
   shouldGenEffectDeps = (): boolean => {
+    // only need to generate effect deps when it's not nested in v-once or v-for
     return !!(
       this.currentRenderEffect &&
       !this.currentRenderEffect.inVOnce &&

packages/compiler-vapor/src/generators/operation.ts

@@ -98,12 +98,14 @@ export function genEffect(
   const { varNamesToDeclare, conditions } = currentRenderEffect!
   const operationsExps = genOperations(operations, context)
 
+  // declare variables: let _foo, _bar
   if (varNamesToDeclare.size) {
     frag.splice(1, 0, `let ${[...varNamesToDeclare].join(', ')};`, NEWLINE)
   }
 
   const newlineCount = operationsExps.filter(frag => frag === NEWLINE).length
   if (newlineCount > 1) {
+    // multiline early return condition: if (_foo === _ctx.foo && _bar === _ctx.bar) return
     const condition: CodeFragment[] =
       conditions.length > 0
         ? [NEWLINE, `if(`, ...conditions.join(' && '), `) return`]
@@ -118,6 +120,7 @@ export function genEffect(
       '})',
     )
   } else {
+    // single line early return condition: _foo !== _ctx.foo && _bar !== _ctx.bar &&
     const condition: CodeFragment[] =
       conditions.length > 0 ? [...conditions.join(' && '), ' && '] : []
     push(...condition, ...operationsExps.filter(frag => frag !== NEWLINE), ')')

packages/compiler-vapor/src/generators/prop.ts

@@ -266,11 +266,14 @@ function processValue(
   const { currentRenderEffect, renderEffectSeemNames } = context
   const { varNamesToDeclare, varNamesOverwritten, conditions, operations } =
     currentRenderEffect!
+
+  // for multiple values the early return condition should be `if (_foo === _ctx.foo) return`
   const oper = operations.length === 1 ? '!==' : '==='
-  for (let frag of values) {
+  for (const frag of values) {
     if (!isArray(frag)) continue
 
-    let [newName, , , rawName] = frag
+    // [code, newlineIndex, loc, name] -> [(_name = code), newlineIndex, loc, name]
+    const [newName, , , rawName] = frag
     if (rawName) {
       let name = rawName.replace(/[^\w]/g, '_')
       if (varNamesOverwritten.has(name)) continue