zstd: Default to full zero frames

[klauspost]

Probably easiest to reference this: klauspost/stdgozstd#1

The decoder still accepts both.

Summary by CodeRabbit

• Bug Fixes
  • Improved encoder default configuration to properly handle zero-length inputs by generating complete frames, enhancing zstandard compression compatibility and ensuring consistent behavior across all input scenarios.

[coderabbitai]

📝 Walkthrough

Walkthrough

The change adds initialization of the fullZero field set to true in the default encoder options. This sets the default behavior for encoding zero-length input as complete zstandard frames within the setDefault() method of the encoderOptions struct.

Changes

Cohort / File(s)	Summary
Encoder Options Configuration zstd/encoder_options.go	Added fullZero: true initialization to the setDefault() method, enabling full frame encoding for zero-length input by default.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'zstd: Default to full zero frames' directly describes the main change: adding fullZero: true to encoder defaults for full zero frame encoding.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch zstd-full-zero-frames

📝 Coding Plan

• Generate coding plan for human review comments

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@zstd/encoder_options.go`:
- Line 45: The empty-frame fast path currently forces Checksum: false even
though fullZero (default true) and crc default may indicate checksums should be
emitted; update the empty branch in EncodeAll (the branch around the empty input
in encoder.go) to propagate the encoder option for crc/checksum instead of
hard-coding false — i.e., read the encoder's checksum/crc option (the same
setting controlled by fullZero/crc) and set Checksum accordingly when
constructing the empty frame response so the advertised checksum behavior
matches non-empty paths.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 9d96f758-617a-431d-a265-7aa57c35a8d9

📥 Commits

Reviewing files that changed from the base of the PR and between bcf0d12 and 3efde7b.

📒 Files selected for processing (1)

• zstd/encoder_options.go