Initial implementation of a Skylark debug server API.

I've pulled out the API for separate review. It includes all
hooks from blaze/skylark used by the debugger.

Debuggable thread contexts are currently declared in 3 places:
- BuildFileAST (top-level evaluation of BUILD files)
- SkylarkRuleConfiguredTargetUtil (rules)
- SkylarkAspectFactory (aspects)

The purpose of declaring these contexts is so that the debugger
can track currently-active threads (and stop tracking them when
the task is completed).

Details of the actual debugging server are in unknown commit.

PiperOrigin-RevId: 197770547

1 files changed, 13 insertions, 5 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleConfiguredTargetUtil.java b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleConfiguredTargetUtil.java
index 1cc7543472..5dd147985f 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleConfiguredTargetUtil.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/skylark/SkylarkRuleConfiguredTargetUtil.java
@@ -43,6 +43,7 @@ import com.google.devtools.build.lib.packages.TargetUtils;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.BaseFunction;
 import com.google.devtools.build.lib.syntax.ClassObject;
+import com.google.devtools.build.lib.syntax.DebugServerUtils;
 import com.google.devtools.build.lib.syntax.Environment;
 import com.google.devtools.build.lib.syntax.EvalException;
 import com.google.devtools.build.lib.syntax.EvalExceptionWithStackTrace;
@@ -92,12 +93,19 @@ public final class SkylarkRuleConfiguredTargetUtil {
               .setEventHandler(ruleContext.getAnalysisEnvironment().getEventHandler())
               .build(); // NB: loading phase functions are not available: this is analysis already,
       // so we do *not* setLoadingPhase().
+
+      final SkylarkRuleContext finalContext = skylarkRuleContext;
       Object target =
-          ruleImplementation.call(
-              /*args=*/ ImmutableList.of(skylarkRuleContext),
-              /*kwargs*/ ImmutableMap.of(),
-              /*ast=*/ null,
-              env);
+          DebugServerUtils.runWithDebuggingIfEnabled(
+              env,
+              () ->
+                  String.format("Target %s", ruleContext.getTarget().getLabel().getCanonicalForm()),
+              () ->
+                  ruleImplementation.call(
+                      /*args=*/ ImmutableList.of(finalContext),
+                      /*kwargs*/ ImmutableMap.of(),
+                      /*ast=*/ null,
+                      env));
 
       if (ruleContext.hasErrors()) {
         return null;