Validation and improved error handling (#359)

* Validation and improved error handling

* Errors no longer stop the world, they are collected, and reported
prettily at the end.
* Added link validation tasks.
* Introduced logger abstraction.

* Added tests and docs for validation

* Fixes from review

* Improved external link error reporting

* If the error is a redirect, reports the location that is being
redirected to.
* If the request to the external link throws an exception, catches and
reports that as an error.

Author: jroper

core/src/main/scala/com/lightbend/paradox/ErrorContext.scala

@@ -0,0 +1,131 @@
+/*
+ * Copyright © 2015 - 2019 Lightbend, Inc. <http://www.lightbend.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.lightbend.paradox
+
+import java.io.File
+
+import com.lightbend.paradox.markdown.Page
+import org.pegdown.ast.Node
+
+import scala.collection.mutable.ListBuffer
+
+trait ErrorContext {
+  def apply(msg: String, index: Int): Unit
+
+  def apply(msg: String, node: Node): Unit = apply(msg, node.getStartIndex)
+
+  def apply(msg: String): Unit
+
+  def apply(msg: String, file: File, index: Int): Unit
+
+  def apply(msg: String, file: File, node: Node): Unit = apply(msg, file, node.getStartIndex)
+
+  def apply(msg: String, file: File): Unit
+
+  def apply(msg: String, page: Page, index: Int): Unit = apply(msg, page.file, index)
+
+  def apply(msg: String, page: Page, node: Node): Unit = apply(msg, page.file, node.getStartIndex)
+
+  def apply(msg: String, page: Page): Unit = apply(msg, page.file)
+}
+
+class ErrorCollector extends ErrorContext {
+  private val errors = new ListBuffer[ParadoxError]()
+
+  private def addError(msg: String, page: Option[File], index: Option[Int]) = {
+    errors.append(ParadoxError(msg, page, index))
+  }
+
+  override def apply(msg: String, index: Int): Unit = throw new IllegalArgumentException("Cannot report an indexed error without a page context")
+
+  override def apply(msg: String): Unit = addError(msg, None, None)
+
+  override def apply(msg: String, file: File, index: Int): Unit = addError(msg, Some(file), Some(index))
+
+  override def apply(msg: String, file: File): Unit = addError(msg, Some(file), None)
+
+  def hasErrors: Boolean = errors.nonEmpty
+
+  def errorCount: Int = errors.toList.distinct.size
+
+  def logErrors(log: ParadoxLogger) = {
+    val totalErrors = errors.toList.distinct
+    // First log general errors
+    totalErrors.foreach {
+      case ParadoxError(msg, None, _) => log.error(msg)
+      case _                          =>
+    }
+    // Now handle page specific errors
+    totalErrors
+      .filter(_.page.isDefined)
+      .groupBy(_.page.get)
+      .toSeq
+      .sortBy(_._1.getAbsolutePath)
+      .foreach {
+        case (page, errors) =>
+          // Load contents of the page
+          val lines = scala.io.Source.fromFile(page)("UTF-8").getLines().toList
+          errors.sortBy(_.index.getOrElse(0)).foreach {
+            case ParadoxError(error, _, Some(idx)) =>
+              val (_, lineNo, colNo, line) = lines.foldLeft((0, 0, 0, None: Option[String])) { (state, line) =>
+                state match {
+                  case (_, _, _, Some(_)) => state
+                  case (total, l, c, None) =>
+                    if (total + line.length < idx) {
+                      (total + line.length + 1, l + 1, c, None)
+                    } else {
+                      (0, l + 1, idx - total + 1, Some(line))
+                    }
+                }
+              }
+
+              log.error(s"$error at ${page.getAbsolutePath}:$lineNo")
+              line.foreach { l =>
+                log.error(l)
+                log.error(l.take(colNo - 1).map { case '\t' => '\t'; case _ => ' ' } + "^")
+              }
+            case ParadoxError(error, _, _) =>
+              log.error(s"$error at ${page.getAbsolutePath}")
+
+          }
+      }
+  }
+}
+
+class PagedErrorContext(context: ErrorContext, page: Page) extends ErrorContext {
+  override def apply(msg: String, index: Int): Unit = context.apply(msg, page, index)
+
+  override def apply(msg: String): Unit = context.apply(msg, page)
+
+  override def apply(msg: String, file: File, index: Int): Unit = context.apply(msg, file, index)
+
+  override def apply(msg: String, file: File): Unit = context.apply(msg, file)
+}
+
+class ThrowingErrorContext extends ErrorContext {
+  override def apply(msg: String, index: Int): Unit = throw ParadoxException(ParadoxError(msg, None, Some(index)))
+
+  override def apply(msg: String): Unit = throw ParadoxException(ParadoxError(msg, None, None))
+
+  override def apply(msg: String, file: File, index: Int): Unit = throw ParadoxException(ParadoxError(msg, Some(file), Some(index)))
+
+  override def apply(msg: String, file: File): Unit = throw ParadoxException(ParadoxError(msg, Some(file), None))
+}
+
+case class ParadoxError(msg: String, page: Option[File], index: Option[Int])
+
+case class ParadoxException(error: ParadoxError) extends RuntimeException(error.msg)

core/src/main/scala/com/lightbend/paradox/ParadoxLogger.scala

@@ -0,0 +1,48 @@
+/*
+ * Copyright © 2015 - 2019 Lightbend, Inc. <http://www.lightbend.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.lightbend.paradox
+
+import java.io.{ PrintWriter, StringWriter }
+
+import scala.collection.immutable.StringOps
+
+trait ParadoxLogger {
+  def debug(t: Throwable): Unit = {
+    // we provide our own implementation because sbt doesn't offer any exception logging at debug
+    val writer = new StringWriter()
+    t.printStackTrace(new PrintWriter(writer))
+    new StringOps(writer.toString).lines.foreach(debug(_))
+  }
+  def debug(msg: => String): Unit
+  def info(msg: => String): Unit
+  def warn(msg: => String): Unit
+  def error(msg: => String): Unit
+}
+
+object NullLogger extends ParadoxLogger {
+  override def debug(msg: => String): Unit = ()
+  override def info(msg: => String): Unit = ()
+  override def warn(msg: => String): Unit = ()
+  override def error(msg: => String): Unit = ()
+}
+
+object PrintlnLogger extends ParadoxLogger {
+  override def debug(msg: => String): Unit = println(s"[debug] $msg")
+  override def info(msg: => String): Unit = println(s"[info] $msg")
+  override def warn(msg: => String): Unit = println(s"[warn] $msg")
+  override def error(msg: => String): Unit = println(s"[error] $msg")
+}