Add expand_if_equal crosstool.proto message

This will be used by LibrariesToLinkValue to switch on many different types of
libraries.

--
PiperOrigin-RevId: 143438434
MOS_MIGRATED_REVID=143438434

3 files changed, 55 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java
index 2c3a139b7c..4e763cb538 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeatures.java
@@ -331,6 +331,17 @@ public class CcToolchainFeatures implements Serializable {
     }
   }
 
+  @Immutable
+  private static class VariableWithValue {
+    public final String variable;
+    public final String value;
+
+    public VariableWithValue(String variable, String value) {
+      this.variable = variable;
+      this.value = value;
+    }
+  }
+
   /**
    * A group of flags. When iterateOverVariable is specified, we assume the variable is a sequence
    * and the flag_group will be expanded repeatedly for every value in the sequence.
@@ -343,6 +354,7 @@ public class CcToolchainFeatures implements Serializable {
     private final ImmutableSet<String> expandIfAllAvailable;
     private final String expandIfTrue;
     private final String expandIfFalse;
+    private final VariableWithValue expandIfEqual;
 
     /**
      * TODO(b/32655571): Cleanup and get rid of usedVariables field once implicit iteration is not
@@ -380,6 +392,13 @@ public class CcToolchainFeatures implements Serializable {
       this.expandIfAllAvailable = ImmutableSet.copyOf(flagGroup.getExpandIfAllAvailableList());
       this.expandIfTrue = Strings.emptyToNull(flagGroup.getExpandIfTrue());
       this.expandIfFalse = Strings.emptyToNull(flagGroup.getExpandIfFalse());
+      if (flagGroup.hasExpandIfEqual()) {
+        this.expandIfEqual = new VariableWithValue(
+            flagGroup.getExpandIfEqual().getVariable(),
+            flagGroup.getExpandIfEqual().getValue());
+      } else {
+        this.expandIfEqual = null;
+      }
     }
     
     @Override
@@ -421,6 +440,14 @@ public class CcToolchainFeatures implements Serializable {
           && variables.getVariable(expandIfFalse).isTruthy()) {
         return false;
       }
+      if (expandIfEqual != null
+          && (!variables.isAvailable(expandIfEqual.variable)
+              || !variables
+                .getVariable(expandIfEqual.variable)
+                .getStringValue(expandIfEqual.variable)
+                .equals(expandIfEqual.value))) {
+        return false;
+      }
       return true;
     }
 
diff --git a/src/main/protobuf/crosstool_config.proto b/src/main/protobuf/crosstool_config.proto
index 190c3f546e..88d280d233 100644
--- a/src/main/protobuf/crosstool_config.proto
+++ b/src/main/protobuf/crosstool_config.proto
@@ -104,6 +104,14 @@ message CToolchain {
     optional string expand_if_true = 5;
 
     optional string expand_if_false = 6;
+
+    optional VariableWithValue expand_if_equal = 7;
+  }
+
+  message VariableWithValue {
+    required string variable = 1;
+
+    required string value = 2;
   }
 
   // A key/value pair to be added as an environment variable. The value of
diff --git a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeaturesTest.java b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeaturesTest.java
index 9efbb6229d..949aa4297b 100644
--- a/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeaturesTest.java
+++ b/src/test/java/com/google/devtools/build/lib/rules/cpp/CcToolchainFeaturesTest.java
@@ -572,6 +572,26 @@ public class CcToolchainFeaturesTest {
   }
 
   @Test
+  public void testExpandIfEqual() throws Exception {
+    assertThat(
+        getCommandLineForFlagGroups(
+            "flag_group {"
+                + "  expand_if_equal: { variable: 'var' value: 'equal_value' }"
+                + "  flag: '-foo_%{var}'"
+                + "}"
+                + "flag_group {"
+                + "  expand_if_equal: { variable: 'var' value: 'non_equal_value' }"
+                + "  flag: '-bar_%{var}'"
+                + "}"
+                + "flag_group {"
+                + "  expand_if_equal: { variable: 'non_existing_var' value: 'non_existing' }"
+                + "  flag: '-baz_%{non_existing_var}'"
+                + "}",
+            createVariables("var", "equal_value")))
+        .containsExactly("-foo_equal_value");
+  }
+
+  @Test
   public void testLegacyListVariableExpansion() throws Exception {
     assertThat(getCommandLineForFlag("%{v}", createVariables("v", "1", "v", "2")))
         .containsExactly("1", "2");