Add JSON conversion for Skylark structs.

This change adds a to_json method on Skylark structs, paralleling the
existing to_proto built-in.

RELNOTES[NEW]: Adds a to_json method to Skylark structs, providing conversion to JSON format.

--
MOS_MIGRATED_REVID=115873229

1 files changed, 44 insertions, 0 deletions

diff --git a/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleClassFunctionsTest.java b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleClassFunctionsTest.java
index 20c9a4c356..dd2bcdcf1a 100644
--- a/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleClassFunctionsTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skylark/SkylarkRuleClassFunctionsTest.java
@@ -571,6 +571,50 @@ public class SkylarkRuleClassFunctionsTest extends SkylarkTestCase {
         "struct(a=DATA_CFG).to_proto()");
   }
 
+  private void checkJson(String from, String expected) throws Exception {
+    Object result = evalRuleClassCode(from);
+    assertEquals(expected, result);
+  }
+
+  @Test
+  public void testJsonBooleanFields() throws Exception {
+    checkJson("struct(name=True).to_json()", "{\"name\":true}");
+    checkJson("struct(name=False).to_json()", "{\"name\":false}");
+  }
+
+  @Test
+  public void testJsonEncoding() throws Exception {
+    checkJson("struct(name='value').to_json()", "{\"name\":\"value\"}");
+    checkJson("struct(name=['a', 'b']).to_json()", "{\"name\":[\"a\",\"b\"]}");
+    checkJson("struct(name=123).to_json()", "{\"name\":123}");
+    checkJson("struct(name=[1, 2, 3]).to_json()", "{\"name\":[1,2,3]}");
+    checkJson("struct(a=struct(b='b')).to_json()", "{\"a\":{\"b\":\"b\"}}");
+    checkJson("struct(a=[struct(b='x'), struct(b='y')]).to_json()",
+        "{\"a\":[{\"b\":\"x\"},{\"b\":\"y\"}]}");
+    checkJson("struct(a=struct(b=struct(c='c'))).to_json()",
+        "{\"a\":{\"b\":{\"c\":\"c\"}}}");
+  }
+
+  @Test
+  public void testJsonEscapes() throws Exception {
+    checkJson("struct(name='a\"b').to_json()", "{\"name\":\"a\\\"b\"}");
+    checkJson("struct(name='a\\'b').to_json()", "{\"name\":\"a'b\"}");
+    checkJson("struct(name='a\\nb').to_json()", "{\"name\":\"a\\nb\"}");
+  }
+
+  @Test
+  public void testJsonNestedListStructure() throws Exception {
+    checkJson("struct(a=[['b']]).to_json()", "{\"a\":[[\"b\"]]}");
+  }
+
+  @Test
+  public void testJsonInvalidStructure() throws Exception {
+    checkErrorContains(
+        "Invalid text format, expected a struct, a string, a bool, or an int but got a "
+        + "ConfigurationTransition for struct field 'a'",
+        "struct(a=DATA_CFG).to_json()");
+  }
+
   @Test
   public void testLabelAttrWrongDefault() throws Exception {
     checkErrorContains(