Add nullable and discriminated_union field encoding coercion

[jar-stripe]

Why?

The sdk-codegen now emits V2RuntimeSchema field encoding descriptors with two new composite kinds — nullable and discriminated_union — that the Ruby runtime's RequestParams coercion layer didn't yet handle. Without these cases, fields wrapped in a nullable or behind a discriminated union would be passed through uncoerced, silently dropping int64_string / decimal_string conversions on nested fields.

What?

• Adds :nullable handling to coerce_composite: defers nil to the existing early-return in coerce_value, then recurses with encoding[:inner] for non-nil values.
• Adds :discriminated_union handling to coerce_composite: reads the discriminator field value from the hash (handles both symbol and string hash keys), looks up the matching variant schema by symbol key, and coerces the entire hash using that variant's schema. Returns the value unchanged if the discriminator field is absent or no variant matches.
• Adds a private coerce_discriminated_union class method to keep the logic self-contained.
• Adds 11 new unit tests covering: nil passthrough, inner-schema recursion, discriminator key lookup with both symbol and string hash keys, missing discriminator, unknown variant, array wrapping discriminated unions, and nullable wrapping discriminated unions.

See Also

Changelog

• Adds support for nullable and discriminated_union field encoding kinds in RequestParams coercion, enabling correct int64_string/decimal_string serialization for fields nested inside nullable wrappers or discriminated unions.

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Pull request overview

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Suppressed comments (2)

test/stripe/discriminated_union_test.rb:71

• This test claims to cover the case where the discriminator is not explicitly supplied, but it passes model: "rgb", so it isn't exercising the behavior described in the comment. Either omit model: and assert it’s not serialized, or change the test name/comment to reflect explicit passing.

      should "default discriminator to the variant name when not explicitly supplied" do
        # When the caller omits `model:`, the initialize default sets @model but
        # the explicit-key tracker does not include it.  Callers who rely on the
        # default must pass the discriminator explicitly for it to appear in the
        # serialized hash; this test documents that expectation.

test/stripe/discriminated_union_test.rb:14

• The fixture comment says callers only need to supply variant-specific fields because the discriminator defaults, but RequestParams#to_h only includes keys that were explicitly set. With the current initialize using @model = model, omitting model: will not serialize the discriminator, so this comment is misleading.

This issue also appears on line 67 of the same file.

    # A standalone union where each variant is a distinct RequestParams class.
    # The discriminator field (model) defaults to the variant name so callers
    # only need to supply the variant-specific fields.