Always use exactly two components in Xcode version featureHEADmaster

When setting the standard Xcode version feature (see
commit eb952d08f76afa907bb34eaf7e1a69899102c523), always use exactly two
components for the version number. Grouping all point releases together
simplifies writing CROSSTOOLs.

Also fix a bug in MockObjcSupport that prevented Xcode version selection
in tests from working properly.

RELNOTES:
The standard `xcode_VERSION` feature now always uses exactly two
components in the version, even if you specify `--xcode_version` with
more or fewer than two.
PiperOrigin-RevId: 208877588

2 files changed, 31 insertions, 9 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/apple/DottedVersion.java b/src/main/java/com/google/devtools/build/lib/rules/apple/DottedVersion.java
index 9919ff757d..e063f3e085 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/apple/DottedVersion.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/apple/DottedVersion.java
@@ -15,6 +15,7 @@
 package com.google.devtools.build.lib.rules.apple;
 
 import com.google.common.base.Joiner;
+import com.google.common.base.Preconditions;
 import com.google.common.base.Splitter;
 import com.google.common.base.Strings;
 import com.google.common.collect.ComparisonChain;
@@ -169,6 +170,31 @@ public final class DottedVersion implements DottedVersionApi<DottedVersion> {
   }
 
   /**
+   * Returns the string representation of this dotted version, padded or truncated to the specified
+   * number of components.
+   *
+   * <p>For example, a dotted version of "7.3.0" will return "7" if one is requested, "7.3" if two
+   * are requested, "7.3.0" if three are requested, and "7.3.0.0" if four are requested.
+   *
+   * @param numComponents a positive number of dot-separated numbers that should be present in the
+   *     returned string representation
+   */
+  public String toStringWithComponents(int numComponents) {
+    Preconditions.checkArgument(numComponents > 0,
+        "Can't serialize as a version with %s components", numComponents);
+    ImmutableList.Builder<Component> stringComponents = ImmutableList.builder();
+    if (numComponents <= components.size()) {
+      stringComponents.addAll(components.subList(0, numComponents));
+    } else {
+      stringComponents.addAll(components);
+      for (int i = components.size(); i < numComponents; i++) {
+        stringComponents.add(ZERO_COMPONENT);
+      }
+    }
+    return Joiner.on('.').join(stringComponents.build());
+  }
+
+  /**
    * Returns the string representation of this dotted version, padded to a minimum number of
    * components if the string representation does not already contain that many components.
    *
@@ -183,14 +209,7 @@ public final class DottedVersion implements DottedVersionApi<DottedVersion> {
    *     the returned string representation
    */
   public String toStringWithMinimumComponents(int numMinComponents) {
-    ImmutableList.Builder<Component> stringComponents = ImmutableList.builder();
-    stringComponents.addAll(components);
-    int numComponents = Math.max(this.numOriginalComponents, numMinComponents);
-    int zeroesToPad = numComponents - components.size();
-    for (int i = 0; i < zeroesToPad; i++) {
-      stringComponents.add(ZERO_COMPONENT);
-    }
-    return Joiner.on('.').join(stringComponents.build());
+    return toStringWithComponents(Math.max(this.numOriginalComponents, numMinComponents));
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java b/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
index f7e7a4a401..40938048a1 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/CompilationSupport.java
@@ -553,8 +553,11 @@ public class CompilationSupport {
     // next release.
     activatedCrosstoolSelectables.add(NO_DSYM_ZIPS_FEATURE_NAME);
 
+    // Add a feature identifying the Xcode version so CROSSTOOL authors can enable flags for
+    // particular versions of Xcode. To ensure consistency across platforms, use exactly two
+    // components in the version number.
     activatedCrosstoolSelectables.add(XCODE_VERSION_FEATURE_NAME_PREFIX
-        + XcodeConfig.getXcodeVersion(ruleContext).toStringWithMinimumComponents(2));
+        + XcodeConfig.getXcodeVersion(ruleContext).toStringWithComponents(2));
 
     activatedCrosstoolSelectables.addAll(ruleContext.getFeatures());