From 54a16f096141710c7cad256d9f715be9fceb71a9 Mon Sep 17 00:00:00 2001
From: Nathan Harmata <nharmata@google.com>
Date: Tue, 13 Dec 2016 17:49:27 +0000
Subject: Rephrase query transformation in terms of composition of
 QueryExpressionMappers.

--
PiperOrigin-RevId: 141904124
MOS_MIGRATED_REVID=141904124
---
 .../build/lib/query2/SkyQueryEnvironment.java      | 10 +--
 .../lib/query2/engine/QueryExpressionMapper.java   | 80 +++++++++++++++++++++-
 2 files changed, 84 insertions(+), 6 deletions(-)

(limited to 'src/main/java/com/google/devtools')

diff --git a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
index 78a850b8e7..9a52eba825 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
@@ -308,7 +308,8 @@ public class SkyQueryEnvironment extends AbstractBlazeQueryEnvironment<Target>
 
   @Override
   public final QueryExpression transformParsedQuery(QueryExpression queryExpression) {
-    QueryExpression transformedQueryExpression = getTransformedQueryExpression(queryExpression);
+    QueryExpressionMapper mapper = getQueryExpressionMapper();
+    QueryExpression transformedQueryExpression = queryExpression.getMapped(mapper);
     LOG.info(String.format(
         "transformed query [%s] to [%s]",
         Ascii.truncate(
@@ -318,14 +319,13 @@ public class SkyQueryEnvironment extends AbstractBlazeQueryEnvironment<Target>
     return transformedQueryExpression;
   }
 
-  protected QueryExpression getTransformedQueryExpression(QueryExpression queryExpression) {
+  protected QueryExpressionMapper getQueryExpressionMapper() {
     if (universeScope.size() != 1) {
-      return queryExpression;
+      return QueryExpressionMapper.identity();
     }
     TargetPattern.Parser targetPatternParser = new TargetPattern.Parser(parserPrefix);
     String universeScopePattern = Iterables.getOnlyElement(universeScope);
-    return queryExpression.getMapped(
-        new RdepsToAllRdepsQueryExpressionMapper(targetPatternParser, universeScopePattern));
+    return new RdepsToAllRdepsQueryExpressionMapper(targetPatternParser, universeScopePattern);
   }
 
   @Override
diff --git a/src/main/java/com/google/devtools/build/lib/query2/engine/QueryExpressionMapper.java b/src/main/java/com/google/devtools/build/lib/query2/engine/QueryExpressionMapper.java
index f04ed1ec4b..0a0336c8af 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/engine/QueryExpressionMapper.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/engine/QueryExpressionMapper.java
@@ -25,7 +25,7 @@ import com.google.devtools.build.lib.query2.engine.QueryEnvironment.Argument;
  * maintain reference-equality, as an optimization). Subclasses of {@link QueryExpressionMapper} can
  * override these methods in order to implement an arbitrary transformation.
  */
-public class QueryExpressionMapper {
+public abstract class QueryExpressionMapper {
   public QueryExpression map(TargetLiteral targetLiteral) {
     return targetLiteral;
   }
@@ -88,5 +88,83 @@ public class QueryExpressionMapper {
   public QueryExpression map(SetExpression setExpression) {
     return setExpression;
   }
+
+  public static QueryExpressionMapper identity() {
+    return IdentityMapper.INSTANCE;
+  }
+
+  public static QueryExpressionMapper compose(
+      QueryExpressionMapper outerMapper, QueryExpressionMapper innerMapper) {
+    return new ComposedQueryExpressionMapper(outerMapper, innerMapper);
+  }
+
+  private static class ComposedQueryExpressionMapper extends QueryExpressionMapper {
+    private QueryExpressionMapper outerMapper;
+    private QueryExpressionMapper innerMapper;
+
+    private ComposedQueryExpressionMapper(
+        QueryExpressionMapper outerMapper,
+        QueryExpressionMapper innerMapper) {
+      this.outerMapper = outerMapper;
+      this.innerMapper = innerMapper;
+    }
+
+    @Override
+    public QueryExpression map(TargetLiteral targetLiteral) {
+      return innerMapper.map(targetLiteral).getMapped(outerMapper);
+    }
+
+    @Override
+    public QueryExpression map(BinaryOperatorExpression binaryOperatorExpression) {
+      return innerMapper.map(binaryOperatorExpression).getMapped(outerMapper);
+    }
+
+    @Override
+    public QueryExpression map(FunctionExpression functionExpression) {
+      return innerMapper.map(functionExpression).getMapped(outerMapper);
+    }
+
+    @Override
+    public QueryExpression map(LetExpression letExpression) {
+      return innerMapper.map(letExpression).getMapped(outerMapper);
+    }
+
+    @Override
+    public QueryExpression map(SetExpression setExpression) {
+      return innerMapper.map(setExpression).getMapped(outerMapper);
+    }
+  }
+
+  private static class IdentityMapper extends QueryExpressionMapper {
+    private static final IdentityMapper INSTANCE = new IdentityMapper();
+
+    private IdentityMapper() {
+    }
+
+    @Override
+    public QueryExpression map(TargetLiteral targetLiteral) {
+      return targetLiteral;
+    }
+
+    @Override
+    public QueryExpression map(BinaryOperatorExpression binaryOperatorExpression) {
+      return binaryOperatorExpression;
+    }
+
+    @Override
+    public QueryExpression map(FunctionExpression functionExpression) {
+      return functionExpression;
+    }
+
+    @Override
+    public QueryExpression map(LetExpression letExpression) {
+      return letExpression;
+    }
+
+    @Override
+    public QueryExpression map(SetExpression setExpression) {
+      return setExpression;
+    }
+  }
 }
 
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