From 09051773461b98d374d1b46dd0a2caa57768ab30 Mon Sep 17 00:00:00 2001
From: Christopher Vogt <oss.nsp@cvogt.org>
Date: Thu, 15 Jun 2017 22:38:53 -0400
Subject: add sbt-resolver like restart feature

---
 README.md                          |  5 +++++
 cbt                                | 16 ++++++++++++++++
 examples/restart/Readme.md         | 10 ++++++++++
 examples/restart/build/build.scala |  4 ++++
 examples/restart/src/Main.scala    |  6 ++++++
 stage1/Stage1Lib.scala             | 15 +++++++++++++++
 stage2/BasicBuild.scala            | 13 +++++++++++++
 7 files changed, 69 insertions(+)
 create mode 100644 examples/restart/Readme.md
 create mode 100644 examples/restart/build/build.scala
 create mode 100644 examples/restart/src/Main.scala

diff --git a/README.md b/README.md
index 94aa2ab..90dd845 100644
--- a/README.md
+++ b/README.md
@@ -226,6 +226,11 @@ To also clear the screen on each run use:
 $ cbt loop clear run
 ```
 
+To call and restart the main method on file change (like sbt-revolver)
+```
+$ cbt direct loop restart
+```
+
 ### Adding tests
 
 The simplest way to add tests is putting a few assertions into the previously
diff --git a/cbt b/cbt
index 4a5b736..e2014ec 100755
--- a/cbt
+++ b/cbt
@@ -290,6 +290,7 @@ stage1 () {
 USER_PRESSED_CTRL_C=130
 
 CBT_LOOP_FILE="$CWD/target/.cbt-loop.tmp"
+CBT_KILL_FILE="$CWD/target/.cbt-kill.tmp"
 if [ $loop -eq 0 ]; then
 	which fswatch >/dev/null 2>/dev/null
 	export fswatch_installed=$?
@@ -305,6 +306,9 @@ while true; do
 	if [ -f "$CBT_LOOP_FILE" ]; then
 		rm "$CBT_LOOP_FILE"
 	fi
+	if [ -f "$CBT_KILL_FILE" ]; then
+		rm "$CBT_KILL_FILE"
+	fi
 	stage1 "$@"
 	if [ ! $loop -eq 0 ] || [ $exitCode -eq $USER_PRESSED_CTRL_C ]; then
 		log "not looping, exiting" "$@"
@@ -316,6 +320,10 @@ while true; do
 		files=
 		if [ -f "$CBT_LOOP_FILE" ]; then
 			files=($(sort "$CBT_LOOP_FILE"))
+		fi
+		pids=
+		if [ -f "$CBT_KILL_FILE" ]; then
+			pids=($(cat "$CBT_KILL_FILE")) # FIXME: should we uniq here?
 			#rm "$CBT_LOOP_FILE"
 		fi
 		echo ""
@@ -326,6 +334,14 @@ while true; do
 			fi
 		done
 		fswatch --one-event "${files[@]}"
+		for pid in "${pids[@]}"; do
+			if [ $pid == "" ]; then
+				echo "warning: empty pid found in pid kill list" 1>&2
+			else
+				log "killing process $pid"
+				kill -KILL $pid
+			fi
+		done
 	fi
 done
 
diff --git a/examples/restart/Readme.md b/examples/restart/Readme.md
new file mode 100644
index 0000000..e4bf1b5
--- /dev/null
+++ b/examples/restart/Readme.md
@@ -0,0 +1,10 @@
+This example's main method simply prints the current process id.
+This can be used to experiment with cbt's restart feature
+(the equivalent to sbt-revolver).
+
+```
+cbt direct loop restart
+```
+
+starts the main method in a separate process and kills it, when
+a change in project, build file or cbt is detected.
diff --git a/examples/restart/build/build.scala b/examples/restart/build/build.scala
new file mode 100644
index 0000000..a18f951
--- /dev/null
+++ b/examples/restart/build/build.scala
@@ -0,0 +1,4 @@
+import cbt._
+class Build(val context: Context) extends BaseBuild{
+  override def dependencies = super.dependencies :+ libraries.cbt.process
+}
\ No newline at end of file
diff --git a/examples/restart/src/Main.scala b/examples/restart/src/Main.scala
new file mode 100644
index 0000000..1c03832
--- /dev/null
+++ b/examples/restart/src/Main.scala
@@ -0,0 +1,6 @@
+object Main extends App {
+  while(true){
+    Thread.sleep(1000)
+    println( "process " + cbt.process.currentProcessId + " is still running" )
+  }
+}
diff --git a/stage1/Stage1Lib.scala b/stage1/Stage1Lib.scala
index ab95a41..89e52b6 100644
--- a/stage1/Stage1Lib.scala
+++ b/stage1/Stage1Lib.scala
@@ -417,6 +417,21 @@ ${sourceFiles.sorted.mkString(" \\\n")}
       StandardOpenOption.APPEND
     )
   }
+
+  /**
+  add process id to a cbt internal list of processes to kill
+  when looping after a file change
+  */
+  def addProcessIdToKillList(cwd: File, processId: Int) = {
+    val file = cwd / "target/.cbt-kill.tmp"
+    file.createNewFile
+    lib.write(
+      file,
+      processId.toString + "\n",
+      StandardOpenOption.APPEND
+    )
+  }
+
   def cached[T]( targetDirectory: File, inputLastModified: Long )( action: () => T ): (Option[T],Long) = {
     val t = targetDirectory
     val start = System.currentTimeMillis
diff --git a/stage2/BasicBuild.scala b/stage2/BasicBuild.scala
index e41545b..3a9c958 100644
--- a/stage2/BasicBuild.scala
+++ b/stage2/BasicBuild.scala
@@ -327,6 +327,19 @@ trait BaseBuild extends BuildInterface with DependencyImplementation with SbtDep
     waitFor()
   }
 
+  /** currently only produces output when run via cbt direct */
+  def restart: Int = {
+    val pid = restart( mainClassOrFail.getName, context.args )
+    System.err.print("started process with pid: ")
+    pid
+  }
+
+  def restart( className: String, args: Seq[String] ): Int = {
+    val ( pid, waitFor, destroy ) = runForked( mainClassOrFail.getName, context.args )
+    lib.addProcessIdToKillList( context.cwd, pid )
+    pid
+  }
+
   protected def runForkedHandles = runForked( mainClassOrFail.getName, context.args )
 
   def runForked( className: String, args: Seq[String] ): ( Int, () => ExitCode, () => ExitCode ) =
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