work around path separator bug

src/main/java/com/styra/opa/OPAClient.java

@@ -82,7 +82,7 @@ public class OPAClient {
      * suitable value for most sidecar style deployments of OPA.
      */
     public OPAClient() {
-        this.sdk = OpaApiClient.builder().serverURL(sdkServerURL).build();
+        this.sdk = OpaApiClient.builder().client(new OPAHTTPClient()).serverURL(sdkServerURL).build();
     }
 
     /**
@@ -92,7 +92,7 @@ public OPAClient() {
      */
     public OPAClient(String opaURL) {
         this.sdkServerURL = opaURL;
-        this.sdk = OpaApiClient.builder().serverURL(opaURL).build();
+        this.sdk = OpaApiClient.builder().client(new OPAHTTPClient()).serverURL(opaURL).build();
     }
 
     /**

src/main/java/com/styra/opa/utils/OPAHTTPClient.java

@@ -14,6 +14,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.net.URI;
 
 import static java.net.http.HttpRequest.Builder;
 
@@ -53,7 +54,6 @@ public OPAHTTPClient() {
     public HttpResponse<InputStream> send(HttpRequest request)
             throws IOException, InterruptedException, URISyntaxException {
 
-
         // At this point, the HTTP request has already been built, so there
         // is no way to add a new header, see:
         //
@@ -62,7 +62,23 @@ public HttpResponse<InputStream> send(HttpRequest request)
         // Consequentially, we need to make a new builder and copy all of the
         // existing request data into it.
 
-        Builder b = HttpRequest.newBuilder(request.uri());
+        // Explicitly expand path separators in the URI, as the SE SDK
+        // sometimes escapes them as %2F. `/` is not a legal character to appear in
+        // a Rego package path or rule head, so we can simply re-expand those path
+        // elements.
+
+        URI oldURI = request.uri();
+        URI newURI = new URI(
+            oldURI.getScheme(),
+            oldURI.getUserInfo(),
+            oldURI.getHost(),
+            oldURI.getPort(),
+            oldURI.getPath().replaceAll("%2F", "/"),
+            oldURI.getQuery(),
+            oldURI.getFragment()
+        );
+
+        Builder b = HttpRequest.newBuilder(newURI);
         b.method(
                 request.method(),
                 request.bodyPublisher().orElse(HttpRequest.BodyPublishers.noBody()));