Export exportable values as we go instead of at the end of evaluation.

This simplifies implementation of attr.* functions and helps make
declared provider implementation simpler.

--
PiperOrigin-RevId: 148867326
MOS_MIGRATED_REVID=148867326

2 files changed, 81 insertions, 16 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 a0f6a33367..b1f079a14b 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
@@ -194,27 +194,52 @@ public class BuildFileAST extends ASTNode {
   public boolean exec(Environment env, EventHandler eventHandler) throws InterruptedException {
     boolean ok = true;
     for (Statement stmt : stmts) {
-      try {
-        stmt.exec(env);
-      } catch (EvalException e) {
+      if (!execTopLevelStatement(stmt, env, eventHandler)) {
         ok = false;
-        // Do not report errors caused by a previous parsing error, as it has already been
-        // reported.
-        if (e.isDueToIncompleteAST()) {
-          continue;
-        }
-        // When the exception is raised from another file, report first the location in the
-        // BUILD file (as it is the most probable cause for the error).
-        Location exnLoc = e.getLocation();
-        Location nodeLoc = stmt.getLocation();
-        eventHandler.handle(Event.error(
-            (exnLoc == null || !nodeLoc.getPath().equals(exnLoc.getPath())) ? nodeLoc : exnLoc,
-            e.getMessage()));
       }
     }
     return ok;
   }
 
+  /**
+   * Executes tol-level statement of this build file in a given Environment.
+   *
+   * <p>If, for any reason, execution of a statement cannot be completed, an {@link EvalException}
+   * is thrown by {@link Statement#exec(Environment)}. This exception is caught here and reported
+   * through reporter. In effect, there is a
+   * "try/except" block around every top level statement. Such exceptions are not ignored, though:
+   * they are visible via the return value. Rules declared in a package containing any error
+   * (including loading-phase semantical errors that cannot be checked here) must also be considered
+   * "in error".
+   *
+   * <p>Note that this method will not affect the value of {@link #containsErrors()}; that refers
+   * only to lexer/parser errors.
+   *
+   * @return true if no error occurred during execution.
+   */
+
+  public boolean execTopLevelStatement(Statement stmt, Environment env,
+      EventHandler eventHandler) throws InterruptedException {
+    try {
+      stmt.exec(env);
+      return true;
+    } catch (EvalException e) {
+      // Do not report errors caused by a previous parsing error, as it has already been
+      // reported.
+      if (e.isDueToIncompleteAST()) {
+        return false;
+      }
+      // When the exception is raised from another file, report first the location in the
+      // BUILD file (as it is the most probable cause for the error).
+      Location exnLoc = e.getLocation();
+      Location nodeLoc = stmt.getLocation();
+      eventHandler.handle(Event.error(
+          (exnLoc == null || !nodeLoc.getPath().equals(exnLoc.getPath())) ? nodeLoc : exnLoc,
+          e.getMessage()));
+      return false;
+    }
+  }
+
   @Override
   public String toString() {
     return "BuildFileAST" + getStatements();
@@ -348,10 +373,20 @@ public class BuildFileAST extends ASTNode {
   @Nullable
   public static Object eval(Environment env, String... input)
       throws EvalException, InterruptedException {
+    BuildFileAST ast = parseAndValidateSkylarkString(env, input);
+    return ast.eval(env);
+  }
+
+  /**
+   * Parses and validates the lines from input and return the the AST
+   * In case of error during validation, it throws an EvalException.
+   */
+  public static BuildFileAST parseAndValidateSkylarkString(Environment env, String[] input)
+      throws EvalException {
     BuildFileAST ast = parseSkylarkString(env.getEventHandler(), input);
     ValidationEnvironment valid = new ValidationEnvironment(env);
     valid.validateAst(ast.getStatements());
-    return ast.eval(env);
+    return ast;
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/syntax/LValue.java b/src/main/java/com/google/devtools/build/lib/syntax/LValue.java
index 22d686bf4e..ecc72073fe 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/LValue.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/LValue.java
@@ -14,6 +14,7 @@
 
 package com.google.devtools.build.lib.syntax;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.devtools.build.lib.events.Location;
 import com.google.devtools.build.lib.util.Preconditions;
 import java.io.Serializable;
@@ -73,6 +74,35 @@ public class LValue implements Serializable {
     }
   }
 
+  /**
+   *  Returns all names bound by this LValue.
+   *
+   *  Examples:
+   *  <ul>
+   *  <li><{@code x = ...} binds x.</li>
+   *  <li><{@code x, [y,z] = ..} binds x, y, z.</li>
+   *  <li><{@code x[5] = ..} does not bind any names.</li>
+   *  </ul>
+   */
+  public ImmutableSet<String> boundNames() {
+    ImmutableSet.Builder<String> result = ImmutableSet.builder();
+    collectBoundNames(expr, result);
+    return result.build();
+  }
+
+  private static void collectBoundNames(Expression lhs, ImmutableSet.Builder<String> result) {
+    if (lhs instanceof Identifier) {
+      result.add(((Identifier) lhs).getName());
+      return;
+    }
+    if (lhs instanceof ListLiteral) {
+      ListLiteral variables = (ListLiteral) lhs;
+      for (Expression expression : variables.getElements()) {
+        collectBoundNames(expression, result);
+      }
+    }
+  }
+
   private static void doAssign(
       Environment env, Location loc, Expression lhs, Object result)
       throws EvalException, InterruptedException {