fix: let union-variant flags whose field is an object take JSON

[Bradenream]

Summary

Some commands expand a union variant into one flag per field (--body-param.<variant>.<field>). The generated metadata declares some of those flags as plain strings although their fields are objects or nullable strings. setFieldByPath cannot store text in those fields, so each failed with cannot convert string to … whatever value it was given; only --body, or the variant's whole-JSON flag, could set them. A survey of all 38 expanded variant fields found 11:

• test turn create --body-param.agent.payload (an object)
• integration connect --body-param.<provider>.credentials, for twilio, ujet, genesys, kustomer, dixa, sunshine and custom-handoff (objects)
• evaluation create --body-param.<type>.description, for boolean, number and string (nullable strings, so plain text failed too)

buildStringField now hands such a flag to buildJSONField, the builder that JSON flags use (internal/flagutil/stringflag.go). An object takes JSON, and a nullable string takes plain text or null. Flags whose field holds text are unchanged.

Before and after

	master	this PR
The 11 flags, run on the built binary	11 fail with cannot convert string to …	11 send their value
--body-param.agent.payload sequential (text for an object)	cannot convert …	invalid value … expected a JSON value, with an example

Test plan

• gofmt, go vet ./... and go test ./... pass; go.mod is unchanged.

• internal/flagutil/stringflag_test.go covers the type rule and the builder:

  • an object;
  • a nullable string, as text and as null;
  • text that stays text;
  • text rejected for an object.

  Without the change, 3 of them fail.

• test/union-variant-flags.test.ts covers the turn payload, Twilio credentials, an evaluation description (text and null) and a bad value. All 4 fail on master.

  • Most cases read the --dry-run body. The credentials case sends its request to a local server instead, because fix: hide camelCase secrets in --dry-run and --debug output #42 hides credentials in the preview.
  • The exit code is not asserted, since fix: stop --dry-run reporting an API error on commands that return 201 #39 fixes dry runs of operations that return 201.

• Full suite with fix: restore vf docs search, and make the test suite hermetic and green #37 applied: 82/82. With fix: restore vf docs search, and make the test suite hermetic and green #37, fix: stop waiting on the silent stdin an agent's shell hands vf #38 and the other three fixes from this batch: 101/101.

• CI: CLI behaviour shows master's 4 existing failures until fix: restore vf docs search, and make the test suite hermetic and green #37 merges.

[Copilot]

Copilot review overview

🟡 Changes recommended

Explicitly supplied empty nullable strings are omitted instead of being sent as empty values.

Review effort: Balanced
Findings: 1

Open (1)

• Preserve explicitly empty descriptions in JSON requests · New

What changed in this PR

Fixes expanded union-variant flags so object and nullable-string fields use the CLI’s existing JSON handling.

Changes:

• Routes non-text targets through the JSON builder, preserving ordinary string behavior.
• Adds unit and CLI regression tests for objects, nullable strings, and invalid input.

File	Description
test/​union-variant-flags.test.ts	Tests request bodies and invalid-value errors.
internal/​flagutil/​stringflag.go	Detects fields that can hold plain text.
internal/​flagutil/​stringflag_test.go	Tests detection and string-builder behavior.
internal/​flagutil/​metadata.go	Delegates non-text string flags to JSON handling.

Files not reviewed (1)

• internal/flagutil/metadata.go: Generated file

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[effervescentia]

Merge activity

• Oct 2, 6:38 PM UTC: The merge label 'merge' was detected. This PR will be added to the Graphite merge queue once it meets the requirements.
• Oct 2, 6:39 PM UTC: effervescentia added this pull request to the Graphite merge queue.
• Oct 2, 6:39 PM UTC: CI is running for this pull request on a draft pull request (#48) due to your merge queue CI optimization settings.
• Oct 2, 6:40 PM UTC: Merged by the Graphite merge queue via draft PR: #48.