Add an option for the number of actions shown in the experimental UI

Currently, the experimental UI always shows the 3 oldest, still running actions.
While this seems a reasonable default, some users requested to be able to change
the number of actions shown. Hence replace the hard-coded value by a flag.

While there, also fix an off-by-one error in deciding when to put the ellipsis
symbol.

--
Change-Id: I037d208360fa1d3f100c99ab1ab1f5fc140138ac
Reviewed-on: https://bazel-review.googlesource.com/#/c/3811
MOS_MIGRATED_REVID=125427168

1 files changed, 12 insertions, 3 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java
index f5fb46d1bb..5343bfa19e 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/ExperimentalStateTracker.java
@@ -48,12 +48,13 @@ import java.util.TreeSet;
  */
 class ExperimentalStateTracker {
 
-  static final int SAMPLE_SIZE = 3;
   static final long SHOW_TIME_THRESHOLD_SECONDS = 3;
   static final String ELLIPSIS = "...";
 
   static final int NANOS_PER_SECOND = 1000000000;
 
+  private int sampleSize = 3;
+
   private String status;
   private String additionalMessage;
 
@@ -101,6 +102,13 @@ class ExperimentalStateTracker {
     this(clock, 0);
   }
 
+  /**
+   * Set the maximal number of actions shown in the progress bar.
+   */
+  void setSampleSize(int sampleSize) {
+    this.sampleSize = sampleSize;
+  }
+
   void buildStarted(BuildStartingEvent event) {
     status = "Loading";
     additionalMessage = "";
@@ -368,10 +376,11 @@ class ExperimentalStateTracker {
         continue;
       }
       count++;
-      if (count > SAMPLE_SIZE) {
+      if (count > sampleSize) {
+        totalCount--;
         break;
       }
-      int width = (count >= SAMPLE_SIZE && count < actionCount) ? targetWidth - 8 : targetWidth - 4;
+      int width = (count >= sampleSize && count < actionCount) ? targetWidth - 8 : targetWidth - 4;
       terminalWriter.newline().append("    " + describeAction(action, nanoTime, width, toSkip));
     }
     if (totalCount < actionCount) {