Skylark debugging protocol: only track paused or stepping threads.

- remove blaze-side thread creation/destruction hooks
- remove ListThreads, ThreadStarted, ThreadEnded events from protocol
- don't track unpaused, not stepping threads in ThreadHandler

The threading model didn't provide useful information -- in practice,
users never want to list currently-running threads, and the debug
client doesn't need to list currently-paused threads, since it receives
each ThreadPaused and ThreadContinued event, so its model is always up to date.

Not tracking thread creation/destruction greatly simplifies the API, and
reduces the blaze-side hooks -- it was also only semi-implemented, as
plenty (/most?) skylark threads were never registered.

The biggest cost to removing this is lack of nice thread names. In
practice, I think the benefits greatly outweigh this cost. If it ever
becomes a problem, there are other lighter-weight ways of communicating
thread names.

TAG_CHANGE_OK=This proto has never yet been used
TYPE_CHANGE_OK=This proto has never yet been used
PiperOrigin-RevId: 201532462

3 files changed, 0 insertions, 47 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/BuildFileAST.java b/src/main/java/com/google/devtools/build/lib/syntax/BuildFileAST.java
index 801013b207..b584c5dc34 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/BuildFileAST.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/BuildFileAST.java
@@ -198,18 +198,6 @@ public class BuildFileAST extends ASTNode {
    * @return true if no error occurred during execution.
    */
   public boolean exec(Environment env, EventHandler eventHandler) throws InterruptedException {
-    try {
-      // Handles debugging BUILD file evaluation
-      // TODO(bazel-team): add support for debugging skylark file evaluation
-      return DebugServerUtils.runWithDebuggingIfEnabled(
-          env, () -> Thread.currentThread().getName(), () -> doExec(env, eventHandler));
-    } catch (EvalException e) {
-      // runWithDebuggingIfEnabled() shouldn't throw EvalException, since doExec() does not
-      throw new AssertionError("Unexpected EvalException", e);
-    }
-  }
-
-  private boolean doExec(Environment env, EventHandler eventHandler) throws InterruptedException {
     boolean ok = true;
     for (Statement stmt : statements) {
       if (!execTopLevelStatement(stmt, env, eventHandler)) {
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/DebugServer.java b/src/main/java/com/google/devtools/build/lib/syntax/DebugServer.java
index 6fe17238cd..ab2823cc46 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/DebugServer.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/DebugServer.java
@@ -20,19 +20,6 @@ import java.util.function.Function;
 public interface DebugServer {
 
   /**
-   * Executes the given callable and returns its result, while making any skylark evaluation visible
-   * to the debugger. This method should be used to evaluate all debuggable Skylark code.
-   *
-   * @param env the Skylark execution environment
-   * @param threadName the descriptive name of the thread
-   * @param callable the callable object whose execution will be tracked
-   * @param <T> the result type of the callable
-   * @return the value returned by the callable
-   */
-  <T> T runWithDebugging(Environment env, String threadName, DebugCallable<T> callable)
-      throws EvalException, InterruptedException;
-
-  /**
    * Shuts down the debug server, closing any open sockets, etc. This can be safely called multiple
    * times.
    */
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/DebugServerUtils.java b/src/main/java/com/google/devtools/build/lib/syntax/DebugServerUtils.java
index 808d10704a..aba83272db 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/DebugServerUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/DebugServerUtils.java
@@ -14,9 +14,7 @@
 
 package com.google.devtools.build.lib.syntax;
 
-import com.google.devtools.build.lib.syntax.DebugServer.DebugCallable;
 import java.util.concurrent.atomic.AtomicReference;
-import java.util.function.Supplier;
 
 /**
  * A helper class for enabling/disabling skylark debugging.
@@ -50,24 +48,4 @@ public final class DebugServerUtils {
     }
     Eval.removeCustomEval();
   }
-
-  /**
-   * Tracks the execution of the given callable object in the debug server.
-   *
-   * <p>If the skylark debugger is not enabled, runs {@code callable} directly.
-   *
-   * @param env the Skylark execution environment
-   * @param threadName the descriptive name of the thread
-   * @param callable the callable object whose execution will be tracked
-   * @param <T> the result type of the callable
-   * @return the value returned by the callable
-   */
-  public static <T> T runWithDebuggingIfEnabled(
-      Environment env, Supplier<String> threadName, DebugCallable<T> callable)
-      throws EvalException, InterruptedException {
-    DebugServer server = instance.get();
-    return server != null
-        ? server.runWithDebugging(env, threadName.get(), callable)
-        : callable.call();
-  }
 }