apollo-client Network error if field is null - graphql

Question

This particular code has been now running without issues for months, this morning, without any relevant change I can pinpoint in our setup or our code I started receiving
ERROR Error: Uncaught (in promise): Error: Network error: Cannot convert undefined or null to object Error: Network error: Cannot convert undefined or null to object
at new ApolloError (ApolloError.js:43)
at eval (QueryManager.js:324)
at eval (QueryManager.js:755)
at Array.forEach (<anonymous>)
at eval (QueryManager.js:754)
at Map.forEach (<anonymous>)
at QueryManager.broadcastQueries (QueryManager.js:749)
at eval (QueryManager.js:251)
at ZoneDelegate.invoke (zone.js:388)
at Object.onInvoke (core.js:4733)
at new ApolloError (ApolloError.js:43)
at eval (QueryManager.js:324)
at eval (QueryManager.js:755)
at Array.forEach (<anonymous>)
...
inline.bundle.js:26 (anonymous) # main.bundle.js:1
This happens because of an error at Object.keys(src).forEach:
var hasOwn = Object.prototype.hasOwnProperty;
export function merge(dest, src) {
Object.keys(src).forEach(function (key) {
var srcVal = src[key];
if (!hasOwn.call(dest, key)) {
dest[key] = srcVal;
}
else if (srcVal && typeof srcVal === 'object') {
merge(dest[key], srcVal);
}
});
}
The error is:
"Cannot convert undefined or null to object"
merge is called from here:
function executeSelectionSet(selectionSet, rootValue, execContext) {
var fragmentMap = execContext.fragmentMap, contextValue = execContext.contextValue, variables = execContext.variableValues;
var result = {};
selectionSet.selections.forEach(function (selection) {
if (!shouldInclude(selection, variables)) {
// Skip this entirely
return;
}
if (isField(selection)) {
var fieldResult = executeField(selection, rootValue, execContext);
var resultFieldKey = resultKeyNameFromField(selection);
if (fieldResult !== undefined) {
if (result[resultFieldKey] === undefined) {
result[resultFieldKey] = fieldResult;
}
else {
merge(result[resultFieldKey], fieldResult);
}
}
}
else {
var fragment = void 0;
if (isInlineFragment(selection)) {
fragment = selection;
}
else {
// This is a named fragment
fragment = fragmentMap[selection.name.value];
if (!fragment) {
throw new Error("No fragment named " + selection.name.value);
}
}
var typeCondition = fragment.typeCondition.name.value;
if (execContext.fragmentMatcher(rootValue, typeCondition, contextValue)) {
var fragmentResult = executeSelectionSet(fragment.selectionSet, rootValue, execContext);
merge(result, fragmentResult);
}
}
});
if (execContext.resultMapper) {
return execContext.resultMapper(result, rootValue);
}
return result;
}
After I identified the field that was being parsed and the fact the it was null valued in the backend I tried to change the value and then the error moved to the next null valued field for the same node. I tried also with other queries and we have the same result.
We are using django and graphene at the backend and apollo-client at the frontend.
I would be grateful for any insight here, I am still trying to understand what has changed between 23:00 yesterday (latest time I tested the code that is now bombing and it all worked) and 1am tonight (time of the automated deployment on our dev server).

Answer 1

I got a similar error last night and for me, I was able to track it down to a change in the graphql-anywhere package from version 4.1.8 to 4.1.9 (updated 2 days ago).
Here is the changelog: https://github.com/apollographql/apollo-client/blob/master/packages/graphql-anywhere/CHANGELOG.md
Adding "graphql-anywhere": "4.1.8", to my package.json file has solved the issue for my app.