fix #10184: Recognize assigment in v-if and do not throw warning

flow/compiler.js

@@ -59,7 +59,7 @@ declare type ModuleOptions = {
 };
 
 declare type ASTModifiers = { [key: string]: boolean };
-declare type ASTIfCondition = { exp: ?string; block: ASTElement };
+declare type ASTIfCondition = { exp: ?string; alias?: string; block: ASTElement };
 declare type ASTIfConditions = Array<ASTIfCondition>;
 
 declare type ASTAttr = {

src/compiler/codegen/index.js

@@ -164,11 +164,21 @@ function genIfConditions (
 
   const condition = conditions.shift()
   if (condition.exp) {
-    return `(${condition.exp})?${
+    let ternaryExp = `(${condition.exp})?${
       genTernaryExp(condition.block)
     }:${
       genIfConditions(conditions, state, altGen, altEmpty)
-    }`
+    }`;
+    if (condition.alias) {
+      // When there is assignment in `condition.exp`
+
+      // Wrap an IIFE (Immediately Invoked Function Expression) so that the variable of `condition.alias` will be local, and therefore no warning will be thrown.
+      return `function(){var ${condition.alias}; return ${ternaryExp}}()`
+    }
+    else {
+      return ternaryExp
+    }
+
   } else {
     return `${genTernaryExp(condition.block)}`
   }

src/compiler/parser/index.js

@@ -26,6 +26,7 @@ export const dirRE = process.env.VBIND_PROP_SHORTHAND
   ? /^v-|^@|^:|^\.|^#/
   : /^v-|^@|^:|^#/
 export const forAliasRE = /([\s\S]*?)\s+(?:in|of)\s+([\s\S]*)/
+export const assignmentInIfRE = /([a-zA-Z][a-zA-Z0-9_$]*)\s+(?:=)\s+([\s\S]*)/
 export const forIteratorRE = /,([^,\}\]]*)(?:,([^,\}\]]*))?$/
 const stripParensRE = /^\(|\)$/g
 const dynamicArgRE = /^\[.*\]$/
@@ -581,6 +582,10 @@ function findPrevElement (children: Array<any>): ASTElement | void {
 }
 
 export function addIfCondition (el: ASTElement, condition: ASTIfCondition) {
+  let m
+  if ((m = condition.exp && condition.exp.match(assignmentInIfRE))){
+    condition.alias = m[1];
+  }
   if (!el.ifConditions) {
     el.ifConditions = []
   }