[SPARK-3138][SQL] sqlContext.parquetFile should be able to take a single file as parameter

```if (!fs.getFileStatus(path).isDir) throw Exception``` make no sense after this commit #1370

be careful if someone is working on SPARK-2551, make sure the new change passes test case ```test("Read a parquet file instead of a directory")```

Author: chutium <teng.qiu@gmail.com>

Closes #2044 from chutium/parquet-singlefile and squashes the following commits:

4ae477f [chutium] [SPARK-3138][SQL] sqlContext.parquetFile should be able to take a single file as parameter

1 files changed, 2 insertions, 5 deletions

diff --git a/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetTypes.scala b/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetTypes.scala
index 1a52377651..2941b97935 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetTypes.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/parquet/ParquetTypes.scala
@@ -394,17 +394,14 @@ private[parquet] object ParquetTypesConverter extends Logging {
       throw new IllegalArgumentException(s"Incorrectly formatted Parquet metadata path $origPath")
     }
     val path = origPath.makeQualified(fs)
-    if (!fs.getFileStatus(path).isDir) {
-      throw new IllegalArgumentException(
-        s"Expected $path for be a directory with Parquet files/metadata")
-    }
-    ParquetRelation.enableLogForwarding()
 
     val children = fs.listStatus(path).filterNot { status =>
       val name = status.getPath.getName
       (name(0) == '.' || name(0) == '_') && name != ParquetFileWriter.PARQUET_METADATA_FILE
     }
 
+    ParquetRelation.enableLogForwarding()
+
     // NOTE (lian): Parquet "_metadata" file can be very slow if the file consists of lots of row
     // groups. Since Parquet schema is replicated among all row groups, we only need to touch a
     // single row group to read schema related metadata. Notice that we are making assumptions that