They way SN is doing this, is rather than just using the EVAM Data Resource which just pulls the data directly based on the definition, they first use the the Fetch EVAM Metadata data resource which pulls the underlying EVAM metadata for a specific definition. This lets us manipulate the EVAM definition within a client script or data broker at runtime, enabling dynamic queries based on things like page properties or user interactions.
After pulling the EVAM Metadata, SN is adding a query to each of the data resources with a scriplet data resource. Create your own data resource of type scriptlet, with inputs for the EVAM Metadata and the query to be used. The output of the Fetch EVAM Metadata will be the input for this resource along with the query. In the SN SOW implementation, source of the query is a little more complex as it depends on the vizualization the user has interacted with, but any encoded query will work, in my case I just have a single state parameter that gets updated based on a field value.
Manipulate EVAM Properties:
[
{
"name": "evam_metadata",
"label": "EVAM Metadata",
"description": "Output of fetch EVAM metadata",
"readOnly": false,
"fieldType": "object",
"mandatory": true,
"defaultValue": ""
},
{
"name": "query",
"label": "Query",
"description": "Query to be updated as template predicate",
"readOnly": false,
"fieldType": "string",
"mandatory": true,
"defaultValue": ""
}
]
Manipulate EVAM Script:
function transform(input) {
var dynamicQuery = input.query.endsWith('^EQ') ? input.query : input.query + '^EQ';
var datasources = input.evam_metadata.datasources;
for (var index in datasources) {
datasources[index].query = dynamicQuery;
}
input.evam_metadata.datasources = datasources;
return input.evam_metadata;
}
The output of the manipulation, which tweaks the EVAM definition with the query, can then be the input for a Fetch EVAM Data type data resource instance, not to be confused with the EVAM Data Resource. Fetch EVAM data has an input for EVAM Metadata which can be set to the output of the manipulate EVAM scriptlet. Cursor, page size, page number and evam filter preference inputs can all be treated like they were with a EVAM Data Resource. FYI, the input data binding will need to be dotwalked to just the definition object; in my case .output.data.GlideCompositeDataMetadata_Query.getMetadata
At this point, we are almost there, we have requested the EVAM data with out dynamically defined EVAM Definition, but it still can't used in a data set component just yet. There is a final step, using the Bind Data to Component data resource on the Fetch EVAM Data output. Its input, GraphQL data should be the output of the fetch. This data resource already exists and basically resolves the items and actions, which is necessary before its usage in a data set components Or in their words:
View Template resolver block of EVAM. Performs following key activities -
a) retrieves the actual view component prop-field map, prop-action map corresponding to each data-item that it gets as input from EVAM Data Fetcher
b) runs over each data-item to
 - resolve values for view component props using prop-field lookup
 - translate or sanitize static values for view component prop
 - resolve view component action from prop-action lookup
c) returns list of component with resolved propValues to render each data-item
At this point, you should be getting EVAM just like you were before, but with an additional layer of query added before the EVAM is run.
@Vegard S Thank you so much for the tip on Service Operations Workspace, I just didn't have the time to dig through different ServiceNow implementations of the EVAM to find one that filters beforehand. If your looking for an example for this working in the wild, you can install the Service Operations Workspace ITSM Applications plugin in a dev environment and check out the Service Operations Workspace experience within UI builder. If you navigate to the Home page, Service desk landing page SNC variant, Overview subpage, you can find the functionality discussed above, check out the data resources.
