fix(pdf): reach deterministic output from the multi-section path, harden the /ID#364
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…den the /ID
Three follow-ups to the deterministic() backend option:
- MultiSectionDocument hard-wired its own default backend, so a configured
PdfFixedLayoutBackend could not reach the section path through the public
API. Add toPdfBytes(FixedLayoutRenderer) and
writePdf(FixedLayoutRenderer, OutputStream) overloads — the multi-section
counterpart of DocumentSession.render(backend); the no-arg methods delegate
to them with the built-in default.
- The /ID seed only covered five info fields joined with spaces, so keywords
and custom metadata were ignored and shifted field boundaries could collide
("A B"+"" vs "A"+"B"). Derive it from the complete info dictionary as
sorted, length-prefixed key/value frames hashed with SHA-256 (first 16
bytes).
- deterministic(Instant) now truncates to whole seconds up front — PDF dates
carry second precision, so a sub-second instant previously pinned a
second-precision date while the /ID used the full-precision value.
New coverage: multi-section byte-identity through GraphCompose.documents(),
sub-second truncation equivalence, field-boundary collision and
keywords/custom-field participation in the /ID.
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Why
Review follow-ups to the reproducible-output option (#363):
MultiSectionDocumentbuilds its own default backend internally, so a user could notpass
PdfFixedLayoutBackend.builder().deterministic(true).build()to the section path —the internal wiring existed, but the public
GraphCompose.documents()surface had no wayto reach it.
/IDseed covered only five info fields joined with spaces: keywords and custommetadata did not participate, and shifted field boundaries collided
(
title="A B", author=""vstitle="A", author="B").deterministic(Instant)kept sub-second precision: PDF dates serialize to whole seconds,so a sub-second instant pinned a second-precision CreationDate while the
/IDwas derivedfrom the full-precision value.
What
MultiSectionDocument.toPdfBytes(FixedLayoutRenderer)andwritePdf(FixedLayoutRenderer, OutputStream)— the multi-section counterpart ofDocumentSession.render(backend); the existing no-arg methods delegate to them with thebuilt-in default, so current callers are unchanged. PDF-specific configuration stays out of
the core API (the parameter is the existing
FixedLayoutRendererseam).PdfDeterminismWriter.documentIdnow canonicalizes the complete info dictionary —every entry participates, as sorted, length-prefixed key/value frames — hashed with
SHA-256, truncated to the 16 bytes a PDF
/IDcarries.Builder.deterministic(Instant)truncates to whole seconds up front, so the serializeddates and the
/IDderive from the same value.Tests
PdfDeterministicOutputTest(6): + multi-section byte-identity through the publicGraphCompose.documents()path, + sub-second instant renders byte-identically to itswhole-second truncation.
PdfDeterminismWriterTest(6): + field-boundary collision stays distinct, + keywords andcustom metadata fields participate in the
/ID../mvnw -f aggregator/pom.xml verify -pl :graph-compose-qa -am— full compile + javadocgate + the qa visual/parity suite (643): green.
The
/IDscheme change is safe pre-release:deterministic(...)is@Betaand unpublished.