From 399e6cdb29cade0e43c7131eff0053a5b6c21037 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Franz=20P=C3=B6schel?= <franz.poeschel@gmail.com>
Date: Tue, 30 May 2023 14:37:48 +0200
Subject: [PATCH] JSON backend: Fail when trying to open non-existing groups

---
 include/openPMD/IO/JSON/JSONIOHandlerImpl.hpp |  2 +-
 src/IO/JSON/JSONIOHandlerImpl.cpp             | 55 +++++++++++++++----
 2 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/include/openPMD/IO/JSON/JSONIOHandlerImpl.hpp b/include/openPMD/IO/JSON/JSONIOHandlerImpl.hpp
index 7f10f62cd9..a6ec202c56 100644
--- a/include/openPMD/IO/JSON/JSONIOHandlerImpl.hpp
+++ b/include/openPMD/IO/JSON/JSONIOHandlerImpl.hpp
@@ -284,7 +284,7 @@ class JSONIOHandlerImpl : public AbstractIOHandlerImpl
 
     // make sure that the given path exists in proper form in
     // the passed json value
-    static void ensurePath(nlohmann::json *json, std::string path);
+    static void ensurePath(nlohmann::json *json, std::string path, Access);
 
     // In order not to insert the same file name into the data structures
     // with a new pointer (e.g. when reopening), search for a possibly
diff --git a/src/IO/JSON/JSONIOHandlerImpl.cpp b/src/IO/JSON/JSONIOHandlerImpl.cpp
index e17e4929eb..7527acd04e 100644
--- a/src/IO/JSON/JSONIOHandlerImpl.cpp
+++ b/src/IO/JSON/JSONIOHandlerImpl.cpp
@@ -23,6 +23,8 @@
 #include "openPMD/Datatype.hpp"
 #include "openPMD/DatatypeHelpers.hpp"
 #include "openPMD/Error.hpp"
+#include "openPMD/IO/Access.hpp"
+#include "openPMD/ThrowError.hpp"
 #include "openPMD/auxiliary/Filesystem.hpp"
 #include "openPMD/auxiliary/Memory.hpp"
 #include "openPMD/auxiliary/StringManip.hpp"
@@ -165,13 +167,13 @@ void JSONIOHandlerImpl::createPath(
         auto filepos = setAndGetFilePosition(writable, false);
 
         jsonVal = &(*jsonVal)[filepos->id];
-        ensurePath(jsonVal, path);
+        ensurePath(jsonVal, path, m_handler->m_backendAccess);
         path = filepos->id.to_string() + "/" + path;
     }
     else
     {
 
-        ensurePath(jsonVal, path);
+        ensurePath(jsonVal, path, m_handler->m_backendAccess);
     }
 
     m_dirty.emplace(file);
@@ -570,7 +572,10 @@ void JSONIOHandlerImpl::openPath(
             std::make_shared<JSONFilePosition>(json::json_pointer(path));
     }
 
-    ensurePath(j, removeSlashes(parameters.path));
+    ensurePath(
+        j,
+        removeSlashes(parameters.path),
+        /* Must not modify j */ Access::READ_ONLY);
 
     writable->written = true;
 }
@@ -1110,18 +1115,46 @@ bool JSONIOHandlerImpl::hasKey(nlohmann::json &j, KeyT &&key)
     return j.find(std::forward<KeyT>(key)) != j.end();
 }
 
-void JSONIOHandlerImpl::ensurePath(nlohmann::json *jsonp, std::string path)
+void JSONIOHandlerImpl::ensurePath(
+    nlohmann::json *jsonp, std::string path, Access access)
 {
     auto groups = auxiliary::split(path, "/");
-    for (std::string &group : groups)
+    if (access::readOnly(access))
     {
-        // Enforce a JSON object
-        // the library will automatically create a list if the first
-        // key added to it is parseable as an int
-        jsonp = &(*jsonp)[group];
-        if (jsonp->is_null())
+        for (std::string const &group : groups)
         {
-            *jsonp = nlohmann::json::object();
+            if (!jsonp->contains(group))
+            {
+                throw error::ReadError(
+                    error::AffectedObject::Group,
+                    error::Reason::NotFound,
+                    "JSON",
+                    "Required group '" + path + "' not present.");
+            }
+            jsonp = &(*jsonp).at(group);
+            if (!jsonp->is_object())
+            {
+                throw error::ReadError(
+                    error::AffectedObject::Group,
+                    error::Reason::UnexpectedContent,
+                    "JSON",
+                    "Required group '" + path +
+                        "' is present, but not a JSON object.");
+            }
+        }
+    }
+    else
+    {
+        for (std::string const &group : groups)
+        {
+            // Enforce a JSON object
+            // the library will automatically create a list if the first
+            // key added to it is parseable as an int
+            jsonp = &(*jsonp)[group];
+            if (jsonp->is_null())
+            {
+                *jsonp = nlohmann::json::object();
+            }
         }
     }
 }