Enum PdfLegStatus 

#[non_exhaustive]
pub enum PdfLegStatus {
    Fetched,
    NoOaUrl,
    Blocked {
        code: ErrorCode,
        message: String,
        denial: Option<DenialContext>,
        suggested_arxiv_id: Option<String>,
    },
    PreprintFallback {
        arxiv_id: String,
        original_block: String,
        found_by: FoundBy,
    },
    PreprintDoiFallback {
        preprint_doi: Doi,
        platform: Option<String>,
        original_block: String,
        found_by: FoundBy,
    },
    TdmFetched {
        source: String,
        original_block: String,
    },
}

Outcome of a successful fetch_paper call.

Wire shape mirrors docs/MCP_TOOLS.md §5 FetchResult minus the envelope chrome the MCP server wraps it in (ok: true, ref, optional error).

path is the absolute path of the resource the orchestrator wrote to the store. For arXiv refs and successful DOI OA-PDF fetches this is <root>/<safekey>.pdf; for the DOI metadata-only fallback (OA URL host off the oa-publisher allowlist, or PDF leg failed for another transport reason — docs/REDIRECT_ALLOWLIST.md §3 informed-best- effort posture) this is <root>/.metadata/<safekey>.toml. Outcome of the DOI OA-PDF leg, carried on FetchPaperOutcome so a caller can NEVER silently report a blocked PDF as a plain “metadata-only” success (issue #118). The product promise is “immediately explain WHY a paper can’t be fetched” — the distinction between “there was no OA PDF to fetch” and “an OA PDF existed but we were blocked, and here is the reason” is exactly that explanation.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Fetched

A PDF was fetched and written to disk (arXiv always; DOI when the OA-publisher leg succeeded).

NoOaUrl

No OA URL was discovered (Unpaywall reported no best_oa_location). Metadata-only is the correct, expected result here — not a failure.

Blocked

An OA URL was discovered but the PDF could not be retrieved (host outside the oa-publisher allowlist, not-a-PDF body, transport failure, …). Metadata was still written, but the caller MUST surface this reason rather than pretending the fetch was a clean metadata-only success.

Fields

code: ErrorCode

Closed-set code, mapped from the underlying transport error via the canonical From<FetchError> for ErrorCode.

message: String

Human-readable one-line reason (the FetchError display).

denial: Option<DenialContext>

Structured denial side-channel (ADR-0023) when the failure was an allowlist / scheme denial; None otherwise.

suggested_arxiv_id: Option<String>

Actionable suggested arXiv ID for the same paper when Unpaywall metadata includes an arXiv alternative but the PDF leg was blocked.

PreprintFallback

The OA publisher PDF was blocked (403, allowlist denial, etc.) but the suggested_arxiv_id pointed to an arXiv preprint that was successfully fetched and stored under the DOI entry (issue #325). The stored PDF came from arXiv, not the publisher; callers SHOULD surface a note so the user knows the file is a preprint.

Fields

arxiv_id: String

The arXiv ID that was successfully fetched as fallback.

original_block: String

The OA-publisher error that triggered the fallback (for logs and audit trail context).

found_by: FoundBy

Who named the preprint: Unpaywall (#325), or the finder that found it when Unpaywall named none (ADR-0062).

PreprintDoiFallback

Nothing open for the DOI itself, and no arXiv preprint: a non-arXiv preprint (bioRxiv, medRxiv, Research Square, OSF, …) was found and fetched through the OA location its own DOI reports (#640).

Fields

preprint_doi: Doi

The preprint’s DOI.

platform: Option<String>

The platform, when the finder named one.

original_block: String

What the DOI’s own content leg ended with.

found_by: FoundBy

Who named the preprint.

TdmFetched

The OA chain was blocked and a Tier-3 TDM source served the publisher’s own copy under the user’s TDM agreement (#458).

Distinct from Self::Fetched on purpose. The bytes did not come from an OA host, they are not necessarily openly licensed, and the user obtained them under an agreement they signed — provenance that says oa-publisher here would be wrong in all three respects.

Fields

source: String

The Tier-3 source that served it ("tdm-aps", …). Matches crate::source::Source::name.

original_block: String

The OA-chain error that triggered the fallback, kept for the audit trail — the user still needs to know the open route failed even though the fetch succeeded.

Trait Implementations

impl Clone for PdfLegStatus

fn clone(&self) -> PdfLegStatus

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PdfLegStatus

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.