Ignore '--no-limit' query changes option for anonymous users

Setting 'maxPages' is not enough to limit resources consumed by the
anonymous users as one can still request low page number with unlimited
result set (adding 'no-limit' option to REST API query changes call).

In order to solve it make 'no-limit' not applicable for anonymous users.
Notes:
* one can still configure them to request unlimited results by setting
  'Query Limit' Global Capability to Integer.MAX_VALUE for 'Anonymous
  Users' group
* 'no-limit' option is only a part of query changes API hence accounts,
  groups and projects are not affected by this change

Release-Notes: Ignore '--no-limit' for anonymous users change queries
Bug: Issue 15563
Change-Id: Ic789690ffd2f94f02989c2906fcd75e442df86f8

Documentation/rest-api-changes.txt

diff --git a/Documentation/rest-api-changes.txt b/Documentation/rest-api-changes.txt
index 2bfb5d5..32bfc6b 100644
--- a/Documentation/rest-api-changes.txt
+++ b/Documentation/rest-api-changes.txt
@@ -74,8 +74,8 @@
 link:user-search.html#_search_operators[query string] must be provided
 by the `q` parameter. The `n` parameter can be used to limit the
 returned results. The `no-limit` parameter can be used remove the default
-limit on queries and return all results. This might not be supported by
-all index backends.
+limit on queries and return all results (does not apply to anonymous requests).
+This might not be supported by all index backends.
 
 As result a list of link:#change-info[ChangeInfo] entries is returned.
 The change output is sorted by the last update time, most recently

java/com/google/gerrit/server/restapi/change/QueryChanges.java

diff --git a/java/com/google/gerrit/server/restapi/change/QueryChanges.java b/java/com/google/gerrit/server/restapi/change/QueryChanges.java
index 3c8157b..7df74f8 100644
--- a/java/com/google/gerrit/server/restapi/change/QueryChanges.java
+++ b/java/com/google/gerrit/server/restapi/change/QueryChanges.java
@@ -27,6 +27,7 @@
 import com.google.gerrit.index.query.QueryParseException;
 import com.google.gerrit.index.query.QueryRequiresAuthException;
 import com.google.gerrit.index.query.QueryResult;
+import com.google.gerrit.server.AnonymousUser;
 import com.google.gerrit.server.CurrentUser;
 import com.google.gerrit.server.DynamicOptions;
 import com.google.gerrit.server.change.ChangeJson;
@@ -95,7 +96,9 @@
     this.start = start;
   }
 
-  @Option(name = "--no-limit", usage = "Return all results, overriding the default limit")
+  @Option(
+      name = "--no-limit",
+      usage = "Return all results, overriding the default limit. Ignored for anonymous users.")
   public void setNoLimit(boolean on) {
     this.noLimit = on;
   }
@@ -168,7 +171,7 @@
     if (start != null) {
       queryProcessor.setStart(start);
     }
-    if (noLimit != null) {
+    if (noLimit != null && !AnonymousUser.class.isAssignableFrom(userProvider.get().getClass())) {
       queryProcessor.setNoLimit(noLimit);
     }
     if (skipVisibility != null) {

javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java

diff --git a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
index 0c30ef5..7c504b8 100644
--- a/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
+++ b/javatests/com/google/gerrit/acceptance/api/change/ChangeIT.java
@@ -2618,7 +2618,7 @@
   }
 
   @Test
-  public void queryChangesNoLimit() throws Exception {
+  public void queryChangesNoLimitRegisteredUser() throws Exception {
     projectOperations
         .allProjectsForUpdate()
         .add(
@@ -2636,6 +2636,26 @@
   }
 
   @Test
+  public void queryChangesNoLimitIgnoredForAnonymousUser() throws Exception {
+    int limit = 2;
+    projectOperations
+        .allProjectsForUpdate()
+        .add(
+            allowCapability(GlobalCapability.QUERY_LIMIT)
+                .group(SystemGroupBackend.ANONYMOUS_USERS)
+                .range(0, limit))
+        .update();
+    for (int i = 0; i < 3; i++) {
+      createChange();
+    }
+    requestScopeOperations.setApiUserAnonymous();
+    List<ChangeInfo> resultsWithDefaultLimit = gApi.changes().query().get();
+    List<ChangeInfo> resultsWithNoLimit = gApi.changes().query().withNoLimit().get();
+    assertThat(resultsWithDefaultLimit).hasSize(limit);
+    assertThat(resultsWithNoLimit).hasSize(limit);
+  }
+
+  @Test
   public void queryChangesStart() throws Exception {
     PushOneCommit.Result r1 = createChange();
     createChange();