What causes "{context}: missing parse arm for {variant}" in Hmbown/CodeWhale?

Add the missing arm to the enum's parse function: `"the-id" | "alias" => Some(Self::Variant)` (for ProviderKind this lives in crates/config/src/provider_kind.rs)

Hmbown/CodeWhale · error · ValueError

{context}: missing parse arm for {variant}

Error message

{context}: missing parse arm for {variant}

What it means

parse_aliases_for_variant could not find a parse arm mapping string literals to the requested enum variant: neither a `"..." => Some(Self::Variant)` pattern inside the enum's `parse` match, nor (for ProviderKind/ApiProvider) a matching provider!() macro invocation in crates/config/src/provider.rs. The checker uses these arms to verify documented aliases, so a variant without a string-parseable identity is treated as a registry inconsistency.

Source

Thrown at scripts/check-provider-registry.py:136

    match_arm = re.search(
        rf'((?:"[^"]+"\s*\|\s*)*"[^"]+")\s*=>\s*Some\(Self::{variant}\)',
        block,
    )
    if match_arm:
        return set(re.findall(r'"([^"]+)"', match_arm.group(1)))
    if enum_name in {"ProviderKind", "ApiProvider"}:
        provider_rs = read(PROVIDER_RS)
        provider_macro = re.search(
            rf'provider!\(\s*\n\s*\w+,\s*\n\s*{variant},\s*\n\s*"([^"]+)".*?'
            r"aliases:\s*\[(.*?)\]\s*\);",
            provider_rs,
            re.DOTALL,
        )
        if provider_macro:
            return {provider_macro.group(1)} | set(
                re.findall(r'"([^"]+)"', provider_macro.group(2))
            )
    raise ValueError(f"{context}: missing parse arm for {variant}")


def provider_kind_ids(config_rs: str) -> dict[str, str]:
    provider_rs = read(PROVIDER_RS)
    pairs = re.findall(
        r"provider!\(\s*\n\s*\w+,\s*\n\s*(\w+),\s*\n\s*\"([^\"]+)\"",
        provider_rs,
    )
    ids: dict[str, str] = {variant: provider_id for variant, provider_id in pairs}
    # Providers with non-fixed wire policy or custom auth behavior use manual
    # impls rather than the provider!() macro.
    for variant_name, id_literal in [
        ("Deepseek", "deepseek"),
        ("DeepseekAnthropic", "deepseek-anthropic"),
        ("OpenaiCodex", "openai-codex"),
        ("Anthropic", "anthropic"),
        ("Openmodel", "openmodel"),
        ("MinimaxAnthropic", "minimax-anthropic"),

View on GitHub (pinned to 8880682c63)

Solutions

Add the missing arm to the enum's parse function: `"the-id" | "alias" => Some(Self::Variant)` (for ProviderKind this lives in crates/config/src/provider_kind.rs)
Or add a provider!() invocation for the variant in crates/config/src/provider.rs with the id string and aliases list, which the checker also reads
Keep arms as plain string-literal patterns — guards or `_ =>` fallbacks are invisible to the check
Update the regexes in parse_aliases_for_variant if the macro shape legitimately changed

Example fix

// before: ProviderKind::Newprovider exists but parse() has no arm for it
// after (crates/config/src/provider_kind.rs, inside parse)
"newprovider" | "new-provider" => Some(Self::Newprovider),

Defensive patterns

Strategy: try-catch

Validate before calling

assert re.search(r'=>\s*Some\(Self::Newprovider\)', provider_kind_rs), 'missing parse arm for Newprovider'

Try / catch

try:
    aliases = parse_aliases_for_variant(...)
except ValueError as e:
    if 'missing parse arm' in str(e):
        add_parse_arm(e)
    raise

Prevention

Every new enum variant needs a string-literal parse arm
Onboard providers through provider!() so the checker sees id and aliases
Run the drift check in CI on changes to config and agent crates

When it happens

Trigger: Adding a new ProviderKind/ApiProvider variant without a parse arm; renaming a variant without updating parse; writing the arm with match guards, wildcards, or intermediate bindings the regex cannot match; changing the provider!() macro's argument shape so the fallback lookup misses too.

Common situations: New-provider onboarding done in the registry but not the parser; refactors of the parse function to data-driven lookups.

Related errors

AI-assisted analysis of Hmbown/CodeWhale@8880682c63 (2026-08-16). Data as JSON: /api/errors/49797669f7b6ec2b. Report an issue: GitHub.