Handle evaluation of statements, not just expressions.

Also handle statements in conditional breakpoints.

This is more consistent with other common debuggers (e.g. java, python).

Calls Parser#parseStatement with local parsing level, so some statement types aren't handled (e.g. load statements), which is broadly consistent with other debuggers.

Assignment, augmented assignment, and return statements return a non-None value,
and simple expression statements still return the result of evaluating the expression.

TAG_CHANGE_OK=This proto has never yet been used
TYPE_CHANGE_OK=This proto has never yet been used
PiperOrigin-RevId: 202135678

2 files changed, 25 insertions, 8 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java b/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java
index 4540f55dfb..ee871e6a05 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Debuggable.java
@@ -22,8 +22,8 @@ import javax.annotation.Nullable;
 /** A context in which debugging can occur. Implemented by Skylark environments. */
 public interface Debuggable {
 
-  /** Evaluates a Skylark expression in the adapter's environment. */
-  Object evaluate(String expression) throws EvalException, InterruptedException;
+  /** Evaluates a Skylark statement in the adapter's environment. */
+  Object evaluate(String statement) throws EvalException, InterruptedException;
 
   /**
    * Returns the stack frames corresponding of the context's current (paused) state.
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/Environment.java b/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
index 5b22906d71..d5b0d6c6f2 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/Environment.java
@@ -29,6 +29,7 @@ import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
 import com.google.devtools.build.lib.skylarkinterface.SkylarkValue;
 import com.google.devtools.build.lib.syntax.Mutability.Freezable;
 import com.google.devtools.build.lib.syntax.Mutability.MutabilityException;
+import com.google.devtools.build.lib.syntax.Parser.ParsingLevel;
 import com.google.devtools.build.lib.util.Fingerprint;
 import com.google.devtools.build.lib.util.Pair;
 import com.google.devtools.build.lib.util.SpellChecker;
@@ -1169,15 +1170,31 @@ public final class Environment implements Freezable, Debuggable {
   }
 
   @Override
-  public Object evaluate(String expression) throws EvalException, InterruptedException {
-    ParserInputSource inputSource =
-        ParserInputSource.create(expression, PathFragment.create("<debug eval>"));
+  public Object evaluate(String contents) throws EvalException, InterruptedException {
+    ParserInputSource input =
+        ParserInputSource.create(contents, PathFragment.create("<debug eval>"));
     EvalEventHandler eventHandler = new EvalEventHandler();
-    Expression expr = Parser.parseExpression(inputSource, eventHandler);
+    Statement statement = Parser.parseStatement(input, eventHandler, ParsingLevel.LOCAL_LEVEL);
     if (!eventHandler.messages.isEmpty()) {
-      throw new EvalException(expr.getLocation(), eventHandler.messages.get(0));
+      throw new EvalException(statement.getLocation(), eventHandler.messages.get(0));
+    }
+    // TODO(bazel-team): move statement handling code to Eval
+    // deal with the most common case first
+    if (statement.kind() == Statement.Kind.EXPRESSION) {
+      return ((ExpressionStatement) statement).getExpression().doEval(this);
+    }
+    // all other statement types are executed directly
+    Eval.fromEnvironment(this).exec(statement);
+    switch (statement.kind()) {
+      case ASSIGNMENT:
+      case AUGMENTED_ASSIGNMENT:
+        return ((AssignmentStatement) statement).getLValue().getExpression().doEval(this);
+      case RETURN:
+        Expression expr = ((ReturnStatement) statement).getReturnExpression();
+        return expr != null ? expr.doEval(this) : Runtime.NONE;
+      default:
+        return Runtime.NONE;
     }
-    return expr.eval(this);
   }
 
   @Override