[SPARK-19402][DOCS] Support LaTex inline formula correctly and fix warnings in Scala/Java APIs generation

## What changes were proposed in this pull request?

This PR proposes three things as below:

- Support LaTex inline-formula, `\( ... \)` in Scala API documentation
  It seems currently,

  ```
  \( ... \)
  ```

  are rendered as they are, for example,

  <img width="345" alt="2017-01-30 10 01 13" src="https://cloud.githubusercontent.com/assets/6477701/22423960/ab37d54a-e737-11e6-9196-4f6229c0189c.png">

  It seems mistakenly more backslashes were added.

- Fix warnings Scaladoc/Javadoc generation
  This PR fixes t two types of warnings as below:

  ```
  [warn] .../spark/sql/catalyst/src/main/scala/org/apache/spark/sql/Row.scala:335: Could not find any member to link for "UnsupportedOperationException".
  [warn]   /**
  [warn]   ^
  ```

  ```
  [warn] .../spark/sql/core/src/main/scala/org/apache/spark/sql/internal/VariableSubstitution.scala:24: Variable var undefined in comment for class VariableSubstitution in class VariableSubstitution
  [warn]  * `${var}`, `${system:var}` and `${env:var}`.
  [warn]      ^
  ```

- Fix Javadoc8 break
  ```
  [error] .../spark/mllib/target/java/org/apache/spark/ml/PredictionModel.java:7: error: reference not found
  [error]  *                       E.g., {link VectorUDT} for vector features.
  [error]                                       ^
  [error] .../spark/mllib/target/java/org/apache/spark/ml/PredictorParams.java:12: error: reference not found
  [error]    *                          E.g., {link VectorUDT} for vector features.
  [error]                                            ^
  [error] .../spark/mllib/target/java/org/apache/spark/ml/Predictor.java:10: error: reference not found
  [error]  *                       E.g., {link VectorUDT} for vector features.
  [error]                                       ^
  [error] .../spark/sql/hive/target/java/org/apache/spark/sql/hive/HiveAnalysis.java:5: error: reference not found
  [error]  * Note that, this rule must be run after {link PreprocessTableInsertion}.
  [error]                                                  ^
  ```

## How was this patch tested?

Manually via `sbt unidoc` and `jeykil build`.

Author: hyukjinkwon <gurwls223@gmail.com>

Closes #16741 from HyukjinKwon/warn-and-break.

5 files changed, 12 insertions, 12 deletions

diff --git a/core/src/main/scala/org/apache/spark/SparkConf.scala b/core/src/main/scala/org/apache/spark/SparkConf.scala
index 308a1ed5fa..fe912e639b 100644
--- a/core/src/main/scala/org/apache/spark/SparkConf.scala
+++ b/core/src/main/scala/org/apache/spark/SparkConf.scala
@@ -262,7 +262,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging with Seria
   /**
    * Get a time parameter as seconds; throws a NoSuchElementException if it's not set. If no
    * suffix is provided then seconds are assumed.
-   * @throws java.util.NoSuchElementException
+   * @throws java.util.NoSuchElementException If the time parameter is not set
    */
   def getTimeAsSeconds(key: String): Long = {
     Utils.timeStringAsSeconds(get(key))
@@ -279,7 +279,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging with Seria
   /**
    * Get a time parameter as milliseconds; throws a NoSuchElementException if it's not set. If no
    * suffix is provided then milliseconds are assumed.
-   * @throws java.util.NoSuchElementException
+   * @throws java.util.NoSuchElementException If the time parameter is not set
    */
   def getTimeAsMs(key: String): Long = {
     Utils.timeStringAsMs(get(key))
@@ -296,7 +296,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging with Seria
   /**
    * Get a size parameter as bytes; throws a NoSuchElementException if it's not set. If no
    * suffix is provided then bytes are assumed.
-   * @throws java.util.NoSuchElementException
+   * @throws java.util.NoSuchElementException If the size parameter is not set
    */
   def getSizeAsBytes(key: String): Long = {
     Utils.byteStringAsBytes(get(key))
@@ -320,7 +320,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging with Seria
   /**
    * Get a size parameter as Kibibytes; throws a NoSuchElementException if it's not set. If no
    * suffix is provided then Kibibytes are assumed.
-   * @throws java.util.NoSuchElementException
+   * @throws java.util.NoSuchElementException If the size parameter is not set
    */
   def getSizeAsKb(key: String): Long = {
     Utils.byteStringAsKb(get(key))
@@ -337,7 +337,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging with Seria
   /**
    * Get a size parameter as Mebibytes; throws a NoSuchElementException if it's not set. If no
    * suffix is provided then Mebibytes are assumed.
-   * @throws java.util.NoSuchElementException
+   * @throws java.util.NoSuchElementException If the size parameter is not set
    */
   def getSizeAsMb(key: String): Long = {
     Utils.byteStringAsMb(get(key))
@@ -354,7 +354,7 @@ class SparkConf(loadDefaults: Boolean) extends Cloneable with Logging with Seria
   /**
    * Get a size parameter as Gibibytes; throws a NoSuchElementException if it's not set. If no
    * suffix is provided then Gibibytes are assumed.
-   * @throws java.util.NoSuchElementException
+   * @throws java.util.NoSuchElementException If the size parameter is not set
    */
   def getSizeAsGb(key: String): Long = {
     Utils.byteStringAsGb(get(key))
diff --git a/core/src/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala b/core/src/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala
index d7bfdbad84..41093bdb85 100644
--- a/core/src/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala
@@ -496,7 +496,7 @@ class PairRDDFunctions[K, V](self: RDD[(K, V)])
    * or `PairRDDFunctions.reduceByKey` will provide much better performance.
    *
    * @note As currently implemented, groupByKey must be able to hold all the key-value pairs for any
-   * key in memory. If a key has too many values, it can result in an [[OutOfMemoryError]].
+   * key in memory. If a key has too many values, it can result in an `OutOfMemoryError`.
    */
   def groupByKey(partitioner: Partitioner): RDD[(K, Iterable[V])] = self.withScope {
     // groupByKey shouldn't use map side combine because map side combine does not
@@ -520,7 +520,7 @@ class PairRDDFunctions[K, V](self: RDD[(K, V)])
    * or `PairRDDFunctions.reduceByKey` will provide much better performance.
    *
    * @note As currently implemented, groupByKey must be able to hold all the key-value pairs for any
-   * key in memory. If a key has too many values, it can result in an [[OutOfMemoryError]].
+   * key in memory. If a key has too many values, it can result in an `OutOfMemoryError`.
    */
   def groupByKey(numPartitions: Int): RDD[(K, Iterable[V])] = self.withScope {
     groupByKey(new HashPartitioner(numPartitions))
diff --git a/core/src/main/scala/org/apache/spark/scheduler/SparkListener.scala b/core/src/main/scala/org/apache/spark/scheduler/SparkListener.scala
index 1b12af7586..4331addb44 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/SparkListener.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/SparkListener.scala
@@ -294,7 +294,7 @@ private[spark] trait SparkListenerInterface {
 
 /**
  * :: DeveloperApi ::
- * A default implementation for [[SparkListenerInterface]] that has no-op implementations for
+ * A default implementation for `SparkListenerInterface` that has no-op implementations for
  * all callbacks.
  *
  * Note that this is an internal interface which might change in different Spark releases.
diff --git a/core/src/main/scala/org/apache/spark/scheduler/package.scala b/core/src/main/scala/org/apache/spark/scheduler/package.scala
index f0dbfc2ac5..4847c41710 100644
--- a/core/src/main/scala/org/apache/spark/scheduler/package.scala
+++ b/core/src/main/scala/org/apache/spark/scheduler/package.scala
@@ -18,7 +18,7 @@
 package org.apache.spark
 
 /**
- * Spark's scheduling components. This includes the [[org.apache.spark.scheduler.DAGScheduler]] and
- * lower level [[org.apache.spark.scheduler.TaskScheduler]].
+ * Spark's scheduling components. This includes the `org.apache.spark.scheduler.DAGScheduler` and
+ * lower level `org.apache.spark.scheduler.TaskScheduler`.
  */
 package object scheduler
diff --git a/core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala b/core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala
index a0f0fdef8e..a150a8e363 100644
--- a/core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala
+++ b/core/src/main/scala/org/apache/spark/storage/TopologyMapper.scala
@@ -60,7 +60,7 @@ class DefaultTopologyMapper(conf: SparkConf) extends TopologyMapper(conf) with L
 
 /**
  * A simple file based topology mapper. This expects topology information provided as a
- * [[java.util.Properties]] file. The name of the file is obtained from SparkConf property
+ * `java.util.Properties` file. The name of the file is obtained from SparkConf property
  * `spark.storage.replication.topologyFile`. To use this topology mapper, set the
  * `spark.storage.replication.topologyMapper` property to
  * [[org.apache.spark.storage.FileBasedTopologyMapper]]