[SPARK-8358] [SQL] Wait for child resolution when resolving generators

Author: Michael Armbrust <michael@databricks.com>

Closes #6811 from marmbrus/aliasExplodeStar and squashes the following commits:

fbd2065 [Michael Armbrust] more style
806a373 [Michael Armbrust] fix style
7cbb530 [Michael Armbrust] [SPARK-8358][SQL] Wait for child resolution when resolving generatorsa

(cherry picked from commit 9073a426e4)
Signed-off-by: Michael Armbrust <michael@databricks.com>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala

@@ -561,7 +561,9 @@ class Analyzer(
     private object AliasedGenerator {
       def unapply(e: Expression): Option[(Generator, Seq[String])] = e match {
         case Alias(g: Generator, name)
-          if g.elementTypes.size > 1 && java.util.regex.Pattern.matches("_c[0-9]+", name) => {
+          if g.resolved &&
+             g.elementTypes.size > 1 &&
+             java.util.regex.Pattern.matches("_c[0-9]+", name) => {
           // Assume the default name given by parser is "_c[0-9]+",
           // TODO in long term, move the naming logic from Parser to Analyzer.
           // In projection, Parser gave default name for TGF as does for normal UDF,
@@ -570,7 +572,7 @@ class Analyzer(
           // Let's simply ignore the default given name for this case.
           Some((g, Nil))
         }
-        case Alias(g: Generator, name) if g.elementTypes.size > 1 =>
+        case Alias(g: Generator, name) if g.resolved && g.elementTypes.size > 1 =>
           // If not given the default names, and the TGF with multiple output columns
           failAnalysis(
             s"""Expect multiple names given for ${g.getClass.getName},

sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala

@@ -132,6 +132,14 @@ class DataFrameSuite extends QueryTest {
     )
   }
 
+  test("explode alias and star") {
+    val df = Seq((Array("a"), 1)).toDF("a", "b")
+
+    checkAnswer(
+      df.select(explode($"a").as("a"), $"*"),
+      Row("a", Seq("a"), 1) :: Nil)
+  }
+
   test("selectExpr") {
     checkAnswer(
       testData.selectExpr("abs(key)", "value"),