Fix support for File objects in proto.encode_text

Follow-up to bazelbuild@5a99b45, which had the effect of adding proto.encode_text
support for File objects - but encoding them very inconveniently (so that they
could not be used as elements of a map or list in the overall object to be
encoded).

Instead, let's use a structure as the encoding proxy object.

Note that this doesn't affect json encoding in any way.

PiperOrigin-RevId: 866110711
Change-Id: Ib4cb1a3df10767a38c5231c5410e5ba816f24151

Author: tetromino

src/main/java/com/google/devtools/build/lib/actions/Artifact.java

@@ -60,6 +60,8 @@
 import net.starlark.java.eval.Printer;
 import net.starlark.java.eval.Starlark;
 import net.starlark.java.eval.StarlarkSemantics;
+import net.starlark.java.eval.Structure;
+import net.starlark.java.lib.MapWrapperStructure;
 import net.starlark.java.lib.StarlarkEncodable;
 
 /**
@@ -717,14 +719,15 @@ public final String toString() {
   }
 
   @Override
-  public Object objectForEncoding(StarlarkSemantics semantics) {
-    return ImmutableMap.of(
-        "path",
-        getExecPathStringForStarlark(semantics),
-        "root",
-        getRootForStarlark(semantics).getExecPathString(),
-        "short_path",
-        getRunfilesPathString());
+  public Structure objectForEncoding(StarlarkSemantics semantics) {
+    return new MapWrapperStructure(
+        ImmutableMap.of(
+            "path",
+            getExecPathStringForStarlark(semantics),
+            "root",
+            getRootForStarlark(semantics).getExecPathString(),
+            "short_path",
+            getRunfilesPathString()));
   }
 
   /** Returns a string representing the complete artifact path information. */

src/main/java/com/google/devtools/build/lib/packages/NativeInfo.java

@@ -17,7 +17,6 @@
 
 import com.google.common.base.Objects;
 import com.google.common.collect.ImmutableMap;
-import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Ordering;
 import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
 import java.util.List;
@@ -29,6 +28,7 @@
 import net.starlark.java.eval.Starlark;
 import net.starlark.java.eval.StarlarkSemantics;
 import net.starlark.java.eval.Structure;
+import net.starlark.java.lib.MapWrapperStructure;
 import net.starlark.java.lib.StarlarkEncodable;
 import net.starlark.java.syntax.Location;
 
@@ -126,60 +126,12 @@ public int hashCode() {
    */
   @Override
   public void repr(Printer printer, StarlarkSemantics semantics) {
-    new EncodableStructure(this).repr(printer, semantics);
+    new MapWrapperStructure(getLegacyFields()).repr(printer, semantics);
   }
 
   @Override
-  public Object objectForEncoding(StarlarkSemantics semantics) {
-    return new EncodableStructure(this);
-  }
-
-  /**
-   * A {@link Structure} wrapper for a {@link NativeInfo}'s non-method fields; used for text
-   * encoding.
-   */
-  private static final class EncodableStructure implements Structure {
-    private final NativeInfo info;
-    private final ImmutableMap<String, Object> fields;
-
-    private EncodableStructure(NativeInfo info) {
-      this.info = info;
-      this.fields = info.getLegacyFields();
-    }
-
-    @Override
-    @Nullable
-    public Object getValue(String name) {
-      return fields.get(name);
-    }
-
-    @Override
-    @Nullable
-    public ImmutableSet<String> getFieldNames() {
-      return fields.keySet();
-    }
-
-    @Override
-    @Nullable
-    public String getErrorMessageForUnknownField(String field) {
-      return info.getProvider().getErrorMessageForUnknownField(field);
-    }
-
-    @Override
-    public void repr(Printer printer, StarlarkSemantics semantics) {
-      boolean first = true;
-      printer.append("struct(");
-      for (var field : fields.entrySet()) {
-        if (!first) {
-          printer.append(", ");
-        }
-        first = false;
-        printer.append(field.getKey());
-        printer.append(" = ");
-        printer.repr(field.getValue(), semantics);
-      }
-      printer.append(")");
-    }
+  public Structure objectForEncoding(StarlarkSemantics semantics) {
+    return new MapWrapperStructure(getLegacyFields());
   }
 
   @Override

src/main/java/net/starlark/java/lib/BUILD

@@ -19,5 +19,7 @@ java_library(
     visibility = ["//src/main/java/net/starlark/java:clients"],
     deps = [
         "//src/main/java/net/starlark/java/eval",
+        "//third_party:guava",
+        "//third_party:jsr305",
     ],
 )

src/main/java/net/starlark/java/lib/MapWrapperStructure.java

@@ -0,0 +1,66 @@
+// Copyright 2026 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 net.starlark.java.lib;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import java.util.Map;
+import javax.annotation.Nullable;
+import net.starlark.java.eval.Printer;
+import net.starlark.java.eval.StarlarkSemantics;
+import net.starlark.java.eval.Structure;
+
+/** A simple {@link Structure} implementation that wraps a map of fields. */
+public class MapWrapperStructure implements Structure {
+  protected final ImmutableMap<String, Object> fields;
+
+  public MapWrapperStructure(Map<String, Object> fields) {
+    this.fields = ImmutableMap.copyOf(fields);
+  }
+
+  @Override
+  @Nullable
+  public Object getValue(String name) {
+    return fields.get(name);
+  }
+
+  @Override
+  @Nullable
+  public ImmutableSet<String> getFieldNames() {
+    return fields.keySet();
+  }
+
+  @Override
+  @Nullable
+  public String getErrorMessageForUnknownField(String field) {
+    return null;
+  }
+
+  @Override
+  public void repr(Printer printer, StarlarkSemantics semantics) {
+    boolean first = true;
+    printer.append("struct(");
+    for (var field : fields.entrySet()) {
+      if (!first) {
+        printer.append(", ");
+      }
+      first = false;
+      printer.append(field.getKey());
+      printer.append(" = ");
+      printer.repr(field.getValue(), semantics);
+    }
+    printer.append(")");
+  }
+}

src/test/java/com/google/devtools/build/lib/starlark/StarlarkRuleClassFunctionsTest.java

@@ -2150,8 +2150,8 @@ public void testJsonInvalidStructure() throws Exception {
   }
 
   @Test
-  public void testJsonFileEncoding() throws Exception {
-    // Test that File objects can be encoded as JSON
+  public void testJsonAndProtoFileEncoding() throws Exception {
+    // Test that File objects can be encoded as JSON and proto.
     scratch.file(
         "test/BUILD",
         """
@@ -2166,20 +2166,30 @@ public void testJsonFileEncoding() throws Exception {
         "test/rule.bzl",
         """
         def _impl(ctx):
-            input = {"file": ctx.file.src, "other": True}
-            expected_output = {
+            json_input = {"file": ctx.file.src, "other": True}
+            json_expected_output = {
                 "file": {
                     "path": ctx.file.src.path,
                     "short_path": ctx.file.src.short_path,
                     "root": ctx.file.src.root.path,
                 },
                 "other": True
             }
-            encoded = json.encode(input)
-            decoded = json.decode(encoded)
+            json_encoded = json.encode(json_input)
+            json_decoded = json.decode(json_encoded)
 
-            if decoded != expected_output:
-                fail("JSON encode/decode of File did not round-trip. Expected: {}, actual: {}".format(expected_output, decoded))
+            if json_decoded != json_expected_output:
+                fail("JSON encode/decode of File did not round-trip. Expected: {}, actual: {}".format(repr(json_expected_output), repr(json_decoded)))
+
+            proto_input = struct(input = json_input)  # proto input must be wrapped in a struct
+            proto_expected_encoded = 'input {\\n  key: "file"\\n  value {\\n    path: "%s"\\n    root: "%s"\\n    short_path: "%s"\\n  }\\n}\\ninput {\\n  key: "other"\\n  value: true\\n}\\n' % (
+                ctx.file.src.path,
+                ctx.file.src.root.path,
+                ctx.file.src.short_path,
+            )
+            proto_encoded = proto.encode_text(proto_input)
+            if proto_encoded != proto_expected_encoded:
+                fail("Proto encoding of File failed. Expected: {}, actual: {}".format(repr(proto_expected_encoded), repr(proto_encoded)))
 
             return []