[SPARK-9093] [SPARKR] Fix single-quotes strings in SparkR

[[SPARK-9093] Fix single-quotes strings in SparkR - ASF JIRA](https://issues.apache.org/jira/browse/SPARK-9093)

This is the result of lintr at the rivision:01155162
[[SPARK-9093] The result of lintr at 01155162](https://gist.github.com/yu-iskw/8c47acf3202796da4d01)

Author: Yu ISHIKAWA <yuu.ishikawa@gmail.com>

Closes #7439 from yu-iskw/SPARK-9093 and squashes the following commits:

61c391e [Yu ISHIKAWA] [SPARK-9093][SparkR] Fix single-quotes strings in SparkR

R/pkg/R/DataFrame.R

@@ -1314,7 +1314,7 @@ setMethod("except",
 #' write.df(df, "myfile", "parquet", "overwrite")
 #' }
 setMethod("write.df",
-          signature(df = "DataFrame", path = 'character'),
+          signature(df = "DataFrame", path = "character"),
           function(df, path, source = NULL, mode = "append", ...){
             if (is.null(source)) {
               sqlContext <- get(".sparkRSQLsc", envir = .sparkREnv)
@@ -1328,7 +1328,7 @@ setMethod("write.df",
             jmode <- callJStatic("org.apache.spark.sql.api.r.SQLUtils", "saveMode", mode)
             options <- varargsToEnv(...)
             if (!is.null(path)) {
-                options[['path']] <- path
+                options[["path"]] <- path
             }
             callJMethod(df@sdf, "save", source, jmode, options)
           })
@@ -1337,7 +1337,7 @@ setMethod("write.df",
 #' @aliases saveDF
 #' @export
 setMethod("saveDF",
-          signature(df = "DataFrame", path = 'character'),
+          signature(df = "DataFrame", path = "character"),
           function(df, path, source = NULL, mode = "append", ...){
             write.df(df, path, source, mode, ...)
           })
@@ -1375,8 +1375,8 @@ setMethod("saveDF",
 #' saveAsTable(df, "myfile")
 #' }
 setMethod("saveAsTable",
-          signature(df = "DataFrame", tableName = 'character', source = 'character',
-                    mode = 'character'),
+          signature(df = "DataFrame", tableName = "character", source = "character",
+                    mode = "character"),
           function(df, tableName, source = NULL, mode="append", ...){
             if (is.null(source)) {
               sqlContext <- get(".sparkRSQLsc", envir = .sparkREnv)

R/pkg/R/SQLContext.R

@@ -457,7 +457,7 @@ dropTempTable <- function(sqlContext, tableName) {
 read.df <- function(sqlContext, path = NULL, source = NULL, schema = NULL, ...) {
   options <- varargsToEnv(...)
   if (!is.null(path)) {
-    options[['path']] <- path
+    options[["path"]] <- path
   }
   if (is.null(source)) {
     sqlContext <- get(".sparkRSQLsc", envir = .sparkREnv)
@@ -506,7 +506,7 @@ loadDF <- function(sqlContext, path = NULL, source = NULL, schema = NULL, ...) {
 createExternalTable <- function(sqlContext, tableName, path = NULL, source = NULL, ...) {
   options <- varargsToEnv(...)
   if (!is.null(path)) {
-    options[['path']] <- path
+    options[["path"]] <- path
   }
   sdf <- callJMethod(sqlContext, "createExternalTable", tableName, source, options)
   dataFrame(sdf)

R/pkg/R/serialize.R

@@ -140,8 +140,8 @@ writeType <- function(con, class) {
                  jobj = "j",
                  environment = "e",
                  Date = "D",
-                 POSIXlt = 't',
-                 POSIXct = 't',
+                 POSIXlt = "t",
+                 POSIXct = "t",
                  stop(paste("Unsupported type for serialization", class)))
   writeBin(charToRaw(type), con)
 }

R/pkg/R/sparkR.R

@@ -140,7 +140,7 @@ sparkR.init <- function(
     if (!file.exists(path)) {
       stop("JVM is not ready after 10 seconds")
     }
-    f <- file(path, open='rb')
+    f <- file(path, open="rb")
     backendPort <- readInt(f)
     monitorPort <- readInt(f)
     close(f)

R/pkg/inst/tests/test_sparkSQL.R

@@ -57,9 +57,9 @@ test_that("infer types", {
   expect_equal(infer_type(as.Date("2015-03-11")), "date")
   expect_equal(infer_type(as.POSIXlt("2015-03-11 12:13:04.043")), "timestamp")
   expect_equal(infer_type(c(1L, 2L)),
-               list(type = 'array', elementType = "integer", containsNull = TRUE))
+               list(type = "array", elementType = "integer", containsNull = TRUE))
   expect_equal(infer_type(list(1L, 2L)),
-               list(type = 'array', elementType = "integer", containsNull = TRUE))
+               list(type = "array", elementType = "integer", containsNull = TRUE))
   testStruct <- infer_type(list(a = 1L, b = "2"))
   expect_equal(class(testStruct), "structType")
   checkStructField(testStruct$fields()[[1]], "a", "IntegerType", TRUE)