THRIFT-6140: Reject malformed short JSON UUID values

[kpumuk]

Ruby JSONProtocol raised EOFError after reading a complete UUID string shorter than 36 characters. Unlike an actual truncated transport value, this represented malformed protocol data, so the exception escaped SimpleServer's per-connection Thrift exception boundary and stopped the serving loop.

This change lets the existing UUID validator classify complete malformed UUID strings as ProtocolException::INVALID_DATA. SimpleServer can then reject the malformed connection and continue accepting clients. Actual truncated JSON input retains its existing EOFError behavior, and valid UUID values continue to round-trip.

Benchmarks

Ruby 4.0.6, pure-Ruby implementation, 200,000 valid JSON UUID decodes per trial, seven trials:

ruby -Ilib -rthrift -e 'payload = %q("550e8400-e29b-41d4-a716-446655440000"); iterations = 200000; times = 7.times.map do; GC.start; started = Process.clock_gettime(Process::CLOCK_MONOTONIC); iterations.times { Thrift::JsonProtocol.new(Thrift::MemoryBufferTransport.new(payload.dup)).read_uuid }; Process.clock_gettime(Process::CLOCK_MONOTONIC) - started; end; sorted = times.sort; puts sorted[times.length / 2]'

Revision	Median
master a9663bc6661a5dd1d99d629e1f269c1907592a1a	3.007022 s
this change	2.908533 s (-3.28%)

The microbenchmark includes transport and protocol object allocation, so small deltas should be treated as noise. It shows no regression in the valid-UUID path.

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Pull request overview

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This PR fixes Ruby JsonProtocol#read_uuid behavior so that complete-but-malformed short UUID strings are rejected as Thrift::ProtocolException::INVALID_DATA (instead of incorrectly surfacing as EOFError), allowing SimpleServer to close just the bad connection and continue serving.

Changes:

• Remove the EOFError length check from JsonProtocol#read_uuid and rely on UUID validation to classify malformed values as INVALID_DATA.
• Restructure/expand UUID validation specs to distinguish fixed-width protocol truncation (EOFError) from JSON malformed-vs-truncated behavior.
• Extend server specs to include a malformed short JSON UUID request to ensure the server loop continues after rejecting it.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
lib/rb/lib/thrift/protocol/json_protocol.rb	Removes the short-UUID EOFError guard so malformed complete UUID strings are handled as protocol invalid data.
lib/rb/spec/uuid_validation_spec.rb	Refactors protocol grouping and adds targeted specs for fixed-width truncation and JSON malformed/truncated UUID cases.
lib/rb/spec/server_spec.rb	Adds a regression test case ensuring malformed short JSON UUID requests don’t stop the server loop.

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