Incorrect cached active tax zone

[hans-rollingridges-dev]

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Describe the bug
In a multi-channel setup, an incorrect cached active tax zone is applied.

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To Reproduce
Steps to reproduce the behavior:

1. npx @vendure/create my-shop-issue-3681

2. Given Default channel

3. Create Demo channel and set default tax and shipping zone to Asia

4. Given Standard Tax Asia

4. Update Standard Tax Europe and set rate to 21%

5. Add product to demo-channel

6. Rebuild products search index

7. Query default-channel shop-api search and note the price with tax is correct

8. Query demo-channel shop-api search and note the price with tax is incorrect

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Expected behavior
It is expected that the indexed products will have a tax rate applied that conforms to the channel's tax zone.

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Test Environment:

• @vendure/core version: 3.3.7
• Nodejs version: v20.19.0
• Database: postgres:16-alpine

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Additional context
I believe the Active Tax Zone request cache key is not integrity safe. This causes integrity to depend on cache invalidation, for example, when looping through channels during product reindexation.

In the short term, I believe the Active Tax Zone cache keys for both ProductPriceApplicator applyChannelPriceAndTax and OrderCalculator applyPriceAdjustments could be as follows to resolve the issue:

private getCacheKey(channel: Channel, order?: Order) {
        return {
            code: 'ActiveTaxZone',
            integrity: {
                channelId: channel.id,
                countryCode: order?.shippingAddress?.countryCode,
            },
        };
    }

In the long term, I believe it would be beneficial for the implemented Tax Zone Strategy itself to be responsible for its caching logic. I believe it's good practice for the consumers of the strategy to be able to clear the cache, and even to disable caching entirely.

The approach used in this repository might be of interest in designing the cache logic: https://github.com/joshuaslate/type-cacheable

[hans-rollingridges-dev]

Updated issue using latest Vendure version 3.3.7

[hans-rollingridges-dev]

Updated issue using a product with only one variant.

[michaelbromley]

Are you using DefaultSearchPlugin or ElasticsearchPlugin?

[hans-rollingridges-dev]

While the issue's reproduction steps use the DefaultSearchPlugin, I've confirmed similar problems occur with a custom ES plugin. The core issue is related to the use of methods like applyChannelPriceAndTax when looping through multiple channels in a single request.