Generated multipart commands cannot upload binary fields other than the payload (e.g. pages deployments create _worker.js) #177

Problem

Generated multipart commands send --file to the payload field only. No other format: binary field in the multipart schema gets a flag, so those fields cannot be sent.

cf pages deployments create shows the problem. Its payload field resolves to _headers, so a Pages Direct Upload cannot include _worker.js, _routes.json, _redirects, _worker.bundle or functions-filepath-routing-config.json. cf pages deploy sends legacy Pages projects to npx wrangler pages deploy, so cf has no way to make an advanced-mode Pages deployment. One case that needs it is keeping a published *.pages.dev hostname while serving the content from a Worker. That needs a _worker.js that forwards to a service binding.

Reproduce (cf 1.0.0-beta.10)

cf pages deployments create my-project --manifest '{}' --branch main --help
# options: --body, --file, --branch, --commit-*, --manifest, --pages-build-output-dir, --wrangler-config-hash
# there is no way to send _worker.js

--file ./_worker.js uploads the file under the _headers field instead.

Proposed fix (ready to merge)

PR creation in this repository is limited to collaborators, so I could not open a pull request. The fix is on this branch:

• Branch: https://github.com/nahwan-kim/cf/tree/fix/multipart-binary-file-flags
• Compare: main...nahwan-kim:cf:fix/multipart-binary-file-flags
• Commit: a single commit, fix: give every binary multipart field its own file flag, with a cf: patch changeset.

What it changes:

• deriveArgsFromOp returns multipartFileFields: one path-valued flag for each binary field other than the payload. Leading _/. are dropped so the names parse as options: --worker-js, --routes-json, --redirects, --worker-bundle, --functions-filepath-routing-config-json. A name that would shadow --file, --body, a global flag, or another derived flag is skipped.
• The flags are wired through the builder, the multipart handler (readFileForFlag + FormData.append with the file name), the dry-run preview (the flags appear in the body and set bodyKind to multipart), and _meta/commands.json.
• pnpm generate changes two commands: pages deployments create and cloudforce-one requests assets upload, which gains --source.

Verification:

• pnpm check passes.
• New MSW test commands/multipart-file-fields.test.ts checks three things: each file reaches its own form field and _headers is not sent; the dry-run preview shows the file flags; an empty file is rejected before any request is made.
• generator/arg-derivation.test.ts covers flag naming and the skipped collisions.
• Live check against a real account: pages deployments create <p> --manifest '{}' --branch main --worker-js ./_worker.js deployed, and <p>.pages.dev served the uploaded worker's response.

Two unrelated test results from the full CLI suite on my machine: commands/auth/profiles.test.ts ("warns that login and logout target default in a bound directory") fails with a snapshot mismatch on unmodified main (45f8332) as well. The two lib/telemetry/dispatcher.test.ts agent tests fail only when an agent environment variable such as AI_AGENT is set.