[Web Components] Facet selection

[nick-nlb]

Description

The various web components contain props to control the data displayed, but until now did not contain the ability to indicate specific facets.

This PR implements the first round of facet-based filtering functionality: the ability to specify facets by ID.

There are three props available, depending on how you wish to apply the facet filtering:

• facetId: If you wish to apply a single facet across all variables, this is the simplest way to do this. It acts as a broadcast value for all variables in the component.
• facetIds: If you wish to apply multiple facet IDs across multiple variables, use facetIds. This takes a space-delimited list of facet IDs (matching the variable list), and applies each facet ID to the respective variable positionally.
• facetMapping: This takes a JSON string mapping variable DCIDs to facet IDs (e.g., '{"Count_Person": "123", "Median_Income_Household": "456"}'). This is the recommended approach for clarity and unambiguity, as it explicitly links a facet to a specific variable regardless of their order in the props.

Conflict Resolution

If a consumer provides multiple facet props simultaneously, the component resolves the facet for each variable using the following order of precedence:

1. facetMapping: The component first checks if the variable has an explicit mapping in this JSON object.
2. facetIds: If not found in the mapping, it checks for a facet ID at the matching index in the facetIds list.
3. facetId: If neither of the above provides a facet ID, it falls back to the global facetId.

Although the resolution order described above is deterministic, it is recommended only to use one of the three in any one component to avoid confusion

Behavior of facetIds (Multiple Variables)

• Single Value Broadcast: As a convenience, if facetIds contains exactly one ID (e.g., facetIds="123"), that ID will be applied to all variables, effectively behaving the same as facetId.
• Partial Lists: If facetIds contains more than one ID but fewer than the number of variables, variables at indices that exceed the list length will fall back to the global facetId (if provided) or default resolution.

Notes

Facet Ids are currently transient in that the same facet may not have the same id over time. This will change in upcoming schema changes. However, in the meantime, use of these props should take this transience into account.

• It is better not to use hard coded facet ids directly within an embedding [i.e., like what we do on the example page] until facet ids become fixed.
• However, you can use this to flexibly update web components, for example, via an external facet selector or via an agent-based tool that uses the web-component to display facet-scoped information, because in those cases, the use of the facet and web component is not permanent, but rather using a facet id that was immediately looked up.

Testing and Examples

There is a page available only on dev that demonstrates this functionality across the various web components.

When running the website locally, you can access this page at:

Dev Example Page

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the web components library by adding support for facet-based filtering. It allows consumers to precisely control which data facets are displayed for specific variables using a flexible set of configuration props. The changes include updates to the component interfaces, the underlying rendering logic, and a new utility function to handle the facet resolution logic consistently across all components.

Highlights

• Facet Filtering Support: Introduced new props (facetId, facetIds, facetMapping) across multiple web components to enable specific facet-based data filtering.
• Deterministic Resolution Logic: Implemented a priority-based resolution system for facet selection, prioritizing explicit mapping, followed by positional lists, and finally a global fallback.
• Developer Experience: Added a new development-only page to demonstrate and test the new facet filtering functionality across various components.

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[gemini-code-assist]

Code Review

This pull request introduces facet filtering capabilities to several web components, including Bar, Highlight, Line, Map, Ranking, and Scatter charts, by adding facetId, facetIds, and facetMapping properties. It also includes a new development route and template to demonstrate these features. A bug was identified in the getFacetId utility function where an early return prevents proper fallback logic when a variable is missing from the mapping. Additionally, it was suggested to optimize performance by parsing the mapping JSON once per render cycle rather than for every variable.

[keyurva]

Thanks Nick! This is very cool. Appreciate the super-fast turnaround!

[keyurva]

nit: Consider wrapping this in a util function like isProd() or isEnvironment('production'). Currently the FLASK_ENV var is accessed from multiple places and starting to keep it confined will be useful.

[nick-nlb]

Good call! There is already a similar util function for checking if we are in a testing environment. I added one in for production that matches, and used it here.

[keyurva]

Is the preference order of various facet parameters documented somewhere? If not, consider capturing it.

[nick-nlb]

Done!