Merge ComposingSplitTransition and ComposingPatchTransition.

Part of https://docs.google.com/document/d/1_UJKmAQ9EE8i3Pl0il3YLTYr-Q9EKYYyLatt2zohfyM/edit#

PiperOrigin-RevId: 198420365

2 files changed, 20 insertions, 110 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/transitions/ComposingPatchTransition.java b/src/main/java/com/google/devtools/build/lib/analysis/config/transitions/ComposingPatchTransition.java
deleted file mode 100644
index 1fec601858..0000000000
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/transitions/ComposingPatchTransition.java
+++ /dev/null
@@ -1,72 +0,0 @@
-// Copyright 2017 The Bazel Authors. All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//    http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package com.google.devtools.build.lib.analysis.config.transitions;
-
-import com.google.common.base.Preconditions;
-import com.google.common.collect.Iterables;
-import com.google.devtools.build.lib.analysis.config.BuildOptions;
-import com.google.devtools.build.lib.skyframe.serialization.autocodec.AutoCodec;
-
-/**
- * A {@link ComposingSplitTransition} that only supports {@link PatchTransition}s
- *
- * <p>Calling code that doesn't want to have to handle splits should prefer this version.
- */
-@AutoCodec
-public class ComposingPatchTransition implements PatchTransition {
-  private final ComposingSplitTransition delegate;
-
-  /**
-   * Creates a {@link ComposingPatchTransition} that applies the sequence: {@code fromOptions ->
-   * transition1 -> transition2 -> toOptions }.
-   *
-   * <p>Note that it's possible to create silly transitions with this constructor (e.g., if one or
-   * both of the transitions is NoTransition). Use composePatchTransitions instead, which checks for
-   * these states and avoids instantiation appropriately.
-   *
-   * @see TransitionResolver#composePatchTransitions
-   */
-  public ComposingPatchTransition(PatchTransition transition1, PatchTransition transition2) {
-    this(new ComposingSplitTransition(transition1, transition2));
-  }
-
-  @AutoCodec.Instantiator
-  ComposingPatchTransition(ComposingSplitTransition delegate) {
-    Preconditions.checkArgument(delegate.isPatchOnly());
-    this.delegate = delegate;
-  }
-
-  @Override
-  public BuildOptions patch(BuildOptions options) {
-    return Iterables.getOnlyElement(delegate.split(options));
-  }
-
-  @Override
-  public String getName() {
-    return delegate.getName();
-  }
-
-  @Override
-  public int hashCode() {
-    return delegate.hashCode();
-  }
-
-  @Override
-  public boolean equals(Object other) {
-    return other instanceof ComposingPatchTransition
-        && ((ComposingPatchTransition) other).delegate.equals(this.delegate);
-  }
-}
-
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/transitions/ComposingSplitTransition.java b/src/main/java/com/google/devtools/build/lib/analysis/config/transitions/ComposingTransition.java
index 4eb6ae0e89..9e0f770a1f 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/transitions/ComposingSplitTransition.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/config/transitions/ComposingTransition.java
@@ -28,42 +28,32 @@ import java.util.Objects;
  * <pre>
  *   transition1: { someSetting = $oldVal + " foo" }
  *   transition2: { someSetting = $oldVal + " bar" }
- *   ComposingSplitTransition(transition1, transition2): { someSetting = $oldVal + " foo bar" }
+ *   ComposingTransition(transition1, transition2): { someSetting = $oldVal + " foo bar" }
  * </pre>
- *
- * <p>Child transitions can be {@link SplitTransition}s, {@link PatchTransition}s, or any
- * combination thereof. We implement this class as a {@link SplitTransition} since that abstraction
- * captures all possible combinations.
  */
 @AutoCodec
-public class ComposingSplitTransition implements SplitTransition {
+public class ComposingTransition implements ConfigurationTransition {
   private ConfigurationTransition transition1;
   private ConfigurationTransition transition2;
 
-  @Override
-  public String getName() {
-    return "(" + transition1.getName() + " + " + transition2.getName() + ")";
-  }
-
   /**
-   * Creates a {@link ComposingSplitTransition} that applies the sequence: {@code fromOptions ->
+   * Creates a {@link ComposingTransition} that applies the sequence: {@code fromOptions ->
    * transition1 -> transition2 -> toOptions }.
    *
    * <p>Note that it's possible to create silly transitions with this constructor (e.g., if one or
-   * both of the transitions is NoTransition). Use composeTransitions instead, which checks for
-   * these states and avoids instantiation appropriately.
-   *
-   * @see TransitionResolver#composeTransitions
+   * both of the transitions is {@link NoTransition}). Use
+   * {@link com.google.devtools.build.lib.analysis.config.TransitionResolver#composeTransitions}
+   * for these cases - it checks for for these states and avoids instantiation appropriately.
    */
   @AutoCodec.Instantiator
-  public ComposingSplitTransition(
+  public ComposingTransition(
       ConfigurationTransition transition1, ConfigurationTransition transition2) {
     this.transition1 = transition1;
     this.transition2 = transition2;
   }
 
   @Override
-  public List<BuildOptions> split(BuildOptions buildOptions) {
+  public List<BuildOptions> apply(BuildOptions buildOptions) {
     ImmutableList.Builder<BuildOptions> toOptions = ImmutableList.builder();
     for (BuildOptions transition1Options : transition1.apply(buildOptions)) {
       toOptions.addAll(transition2.apply(transition1Options));
@@ -72,32 +62,24 @@ public class ComposingSplitTransition implements SplitTransition {
   }
 
   @Override
-  public int hashCode() {
-    return Objects.hash(transition1, transition2);
+  public String reasonForOverride() {
+    return "Basic abstraction for combining other transitions";
   }
 
   @Override
-  public boolean equals(Object other) {
-    return other instanceof ComposingSplitTransition
-        && ((ComposingSplitTransition) other).transition1.equals(this.transition1)
-        && ((ComposingSplitTransition) other).transition2.equals(this.transition2);
+  public String getName() {
+    return "(" + transition1.getName() + " + " + transition2.getName() + ")";
   }
 
-  /**
-   * Returns whether this transition contains only patches (and is thus suitable as a delegate
-   * for {@link ComposingPatchTransition}).
-   */
-  public boolean isPatchOnly() {
-    return transition1 instanceof PatchTransition && transition2 instanceof PatchTransition;
+  @Override
+  public int hashCode() {
+    return Objects.hash(transition1, transition2);
   }
 
-  /**
-   * Allows this transition to be used in patch-only contexts if it contains only
-   * {@link PatchTransition}s.
-   *
-   * <p>Can only be called if {@link #isPatchOnly()} returns true.
-   */
-  public ComposingPatchTransition asPatch() {
-    return new ComposingPatchTransition(this);
+  @Override
+  public boolean equals(Object other) {
+    return other instanceof ComposingTransition
+        && ((ComposingTransition) other).transition1.equals(this.transition1)
+        && ((ComposingTransition) other).transition2.equals(this.transition2);
   }
 }