ref(auth): remove unused code

[nora-shap]

TL;DR

The ConfirmEmail pipeline view contains a returning-user "email override" and an "enter your email" form (ConfirmEmailForm). Both are vestigial.

The ConfirmEmail form began as "let users type an email when GitHub gives none" idea (2015-07), but the /user/emails fallback (2015-09) covered that case before the form even shipped (2015-10). What remained was a returning-user override that (a) never persisted and (b) fed a login path that ignores the email. It has been effectively inert for its entire ~11-year life, which is why nobody noticed: returning users are matched by GitHub id, so the email value never mattered.

Net: this code does not do the thing its shape implies. Removing the override and the form changes no real behavior. This document traces exactly how it got here.

What the code looks like today

class ConfirmEmail(AuthView):
    def handle(self, request, pipeline):
        user = pipeline.fetch_state("user")
        assert user is not None

        # TODO(dcramer): this isn't ideal, but our current flow doesnt really
        # support this behavior;
        try:
            auth_identity = AuthIdentity.objects.select_related("user").get(
                auth_provider=pipeline.provider_model, ident=user["id"]
            )
        except AuthIdentity.DoesNotExist:
            pass
        else:
            user["email"] = auth_identity.user.email      # (A) local-only mutation, never bind_state'd

        if user.get("email"):
            return pipeline.next_step()

        form = ConfirmEmailForm(request.POST or None)     # (B) reachable only if (A) set email to ""
        if form.is_valid():
            user["email"] = form.cleaned_data["email"]
            pipeline.bind_state("user", user)
            return pipeline.next_step()
        return self.respond("sentry_auth_github/enter-email.html", {"form": form})

Why it doesn't do what it looks like

1. FetchUser already guarantees an email. The SSO pipeline steps are [OAuth2Login, OAuth2Callback, FetchUser, ConfirmEmail]. The preceding step, FetchUser, returns pipeline.error(...) if it finds 0 or >1 primary emails. So by the time ConfirmEmail runs, user["email"] is never empty.

2. The override is not persisted. The else branch mutates the local copy but never calls bind_state, so the write never reaches Redis. The next reader (build_identity via finish_pipeline) re-reads the original FetchUser email from the pipeline state.

3. Even then, the collected email is discarded. A returning user resolves to AuthIdentityHandler.handle_existing_identity, which updates and logs in auth_identity.user by id. It never reads identity["email"] or writes user.email. So the form throws away FetchUser's valid GitHub email, prompts for a replacement, and then that replacement goes nowhere.

How we got here (archaeology)

All original logic predates the sentry monorepo — it was authored in the now-archived getsentry/sentry-auth-github plugin.

• a454f01 2015-07-20 — Initial commit. FetchUser binds user data; no email logic, no ConfirmEmail.
• 28c885c 2015-09-20 — "handling hidden emails." Adds the /user/emails primary-email fallback to FetchUser. From here on, FetchUser yields an email or hard-errors.
• 0e8b604 2015-10-15 — "Handle hidden email addresses / Cleanup forms" Introduces ConfirmEmail exactly as it exists today. Because the /user/emails fallback had shipped 3 weeks earlier, the form was only reachable via the blank-email-returning-user edge, and the override was a non-persisting local mutation.

Why removal is safe

• New users: never reach the form (FetchUser guarantees an email or errors). Unaffected.
• Returning users (active): matched by id in handle_existing_identity; identity email ignored. Without the override they keep FetchUser's GitHub email (still ignored) and log in identically.
• Returning users with blank User.email: today they're shown a pointless form whose result is discarded; after removal they simply log in by id. Strictly no worse.
• Returning-but-inactive users (the one path where identity email is consumed, via handle_unknown_identity): removal is actually better — resolution uses FetchUser's real GitHub email instead of a form-typed one.

[linear-code]

ID-1752

[nora-shap]

bugbot run

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[nora-shap]

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