[Entitlements] Fix PolicyUtils and PolicyUtilsTests on Windows (#126185)

This PR fixes 2 issues discovered around PolicyUtils (and PolicyUtilsTests) when running CI on Windows:
- in tests, absolute paths like always are different, this fix updates the tests to account for the difference.
- on Windows, Files.move was failing because we were parsing the Entitlement policy but not closing the stream in a timely manner. This causes plugin installation (and related CI tests) to fail 70% of the time. Fixed by closing the stream properly

Fixes #126176

Author: ldematte

libs/entitlement/src/main/java/org/elasticsearch/entitlement/runtime/policy/PolicyUtils.java

@@ -141,7 +141,9 @@ private static void validatePolicyScopes(String layerName, Policy policy, Set<St
     public static Policy parsePolicyIfExists(String pluginName, Path pluginRoot, boolean isExternalPlugin) throws IOException {
         Path policyFile = pluginRoot.resolve(POLICY_FILE_NAME);
         if (Files.exists(policyFile)) {
-            return new PolicyParser(Files.newInputStream(policyFile, StandardOpenOption.READ), pluginName, isExternalPlugin).parsePolicy();
+            try (var inputStream = Files.newInputStream(policyFile, StandardOpenOption.READ)) {
+                return new PolicyParser(inputStream, pluginName, isExternalPlugin).parsePolicy();
+            }
         }
         return new Policy(pluginName, List.of());
     }

libs/entitlement/src/main/java/org/elasticsearch/entitlement/runtime/policy/entitlements/FilesEntitlement.java

@@ -16,6 +16,7 @@
 import org.elasticsearch.entitlement.runtime.policy.Platform;
 import org.elasticsearch.entitlement.runtime.policy.PolicyValidationException;
 
+import java.nio.file.FileSystems;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.HashMap;
@@ -31,6 +32,8 @@
  */
 public record FilesEntitlement(List<FileData> filesData) implements Entitlement {
 
+    public static final String SEPARATOR = FileSystems.getDefault().getSeparator();
+
     public static final FilesEntitlement EMPTY = new FilesEntitlement(List.of());
 
     public enum Mode {
@@ -160,7 +163,7 @@ public FileData withPlatform(Platform platform) {
 
         @Override
         public String description() {
-            return Strings.format("[%s] <%s>/%s%s", mode, baseDir, relativePath, exclusive ? " (exclusive)" : "");
+            return Strings.format("[%s] <%s>%s%s%s", mode, baseDir, SEPARATOR, relativePath, exclusive ? " (exclusive)" : "");
         }
     }
 
@@ -192,7 +195,7 @@ public FileData withPlatform(Platform platform) {
 
         @Override
         public String description() {
-            return Strings.format("[%s] <%s>/<%s>%s", mode, baseDir, setting, exclusive ? " (exclusive)" : "");
+            return Strings.format("[%s] <%s>%s<%s>%s", mode, baseDir, SEPARATOR, setting, exclusive ? " (exclusive)" : "");
         }
     }
 

libs/entitlement/src/test/java/org/elasticsearch/entitlement/runtime/policy/PolicyUtilsTests.java

@@ -27,6 +27,7 @@
 import java.util.List;
 import java.util.Set;
 
+import static org.elasticsearch.entitlement.runtime.policy.entitlements.FilesEntitlement.SEPARATOR;
 import static org.elasticsearch.test.LambdaMatchers.transformedMatch;
 import static org.hamcrest.Matchers.both;
 import static org.hamcrest.Matchers.containsInAnyOrder;
@@ -317,6 +318,7 @@ public void testFormatPolicyWithMultipleScopes() {
     /** Test that we can format some simple files entitlement properly */
     public void testFormatFilesEntitlement() {
         var pathAB = Path.of("/a/b");
+        var pathCD = Path.of("c/d");
         var policy = new Policy(
             "test-plugin",
             List.of(
@@ -326,11 +328,7 @@ public void testFormatFilesEntitlement() {
                         new FilesEntitlement(
                             List.of(
                                 FilesEntitlement.FileData.ofPath(pathAB, FilesEntitlement.Mode.READ_WRITE),
-                                FilesEntitlement.FileData.ofRelativePath(
-                                    Path.of("c/d"),
-                                    FilesEntitlement.BaseDir.DATA,
-                                    FilesEntitlement.Mode.READ
-                                )
+                                FilesEntitlement.FileData.ofRelativePath(pathCD, FilesEntitlement.BaseDir.DATA, FilesEntitlement.Mode.READ)
                             )
                         )
                     )
@@ -353,7 +351,17 @@ public void testFormatFilesEntitlement() {
             )
         );
         Set<String> actual = PolicyUtils.getEntitlementsDescriptions(policy);
-        assertThat(actual, containsInAnyOrder("files [READ_WRITE] " + pathAB, "files [READ] <DATA>/c/d", "files [READ] <DATA>/<setting>"));
+        var pathABString = pathAB.toAbsolutePath().toString();
+        var pathCDString = SEPARATOR + pathCD.toString();
+        var pathSettingString = SEPARATOR + "<setting>";
+        assertThat(
+            actual,
+            containsInAnyOrder(
+                "files [READ_WRITE] " + pathABString,
+                "files [READ] <DATA>" + pathCDString,
+                "files [READ] <DATA>" + pathSettingString
+            )
+        );
     }
 
     /** Test that we can format some simple files entitlement properly */