mirror of
https://github.com/denizsafak/abogen.git
synced 2026-07-18 05:40:26 +02:00
Artem Akymenko
780e9bd780
Delete legacy backend infrastructure: - abogen/tts_backend.py (TTSBackend protocol, TTSBackendMetadata) - abogen/tts_backend_registry.py (TTSBackendRegistry, global singleton, register_backend) - abogen/tts_backends/ (kokoro.py, supertonic.py, __init__.py) Delete legacy tests: - tests/test_tts_backend.py - tests/test_kokoro_backend.py - tests/test_voice_formula_resolution.py - tests/test_tts_supertonic_unsupported_chars.py Production code now uses only Plugin Architecture via create_pipeline(). All contract, behavioral, and integration tests pass. 2 pre-existing failures in test_supertonic_plugin.py (mock engine mismatch).
90 lines
3.6 KiB
Markdown
90 lines
3.6 KiB
Markdown
# Architecture Amendment #1: EngineConfig — `lang_code` field
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**Date:** 2026-07-12
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**Status:** Accepted
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**PR:** #12 (Normalize Pipeline Public API)
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## Summary
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Add `lang_code: str = "a"` to `EngineConfig` and update its definition to clarify the architectural contract.
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## Background
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During migration from the old `KokoroBackend` to the Plugin Architecture, the `lang_code` parameter became a dead argument. The old backend read it from `**kwargs` and passed it to `KPipeline(lang_code=...)`. The new `KokoroPlugin.create_engine()` hardcodes `lang_code="a"`, ignoring the config entirely. Callers continued passing `lang_code` to `create_pipeline()`, unaware it had no effect.
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This is a functional regression relative to the pre-Plugin Architecture behavior.
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## Decision
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### 1. Updated EngineConfig definition
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**Before:**
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```
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Immutable value object for engine initialization settings.
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Contains only engine-specific settings, no resource references.
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```
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**After:**
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```
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Immutable configuration of an Engine instance.
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Contains parameters that define how a particular Engine instance is
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created and that remain constant throughout the lifetime of that Engine.
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Plugin implementations may ignore fields that are not applicable to them.
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```
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### 2. New field
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```python
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@dataclass(frozen=True)
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class EngineConfig:
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device: str = "cpu"
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lang_code: str = "a"
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```
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### 3. Architectural rules
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- **Fields in EngineConfig are optional unless explicitly required by a plugin.**
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- **Plugins MUST ignore unsupported EngineConfig fields.**
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- **All parameters that may vary between individual synthesis requests must remain in `SynthesisRequest.parameters`.**
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## Rationale
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Analysis of real TTS engines (Kokoro, Piper, XTTS, Coqui, StyleTTS2, Fish Speech) confirmed:
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| Parameter type | Where it belongs | Example |
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|---------------|-----------------|---------|
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| Engine instance config (immutable) | `EngineConfig` | `device`, `lang_code` |
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| Synthesis parameters (per-request) | `SynthesisRequest.parameters` | `speed`, `split_pattern`, `total_steps` |
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`lang_code` determines the engine's behavior at creation time and cannot be changed during the engine's lifetime. It is not a synthesis parameter.
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## Impact on existing plugins
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| Plugin | `device` | `lang_code` | Notes |
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|--------|----------|-------------|-------|
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| Kokoro | Reads ✓ | Reads ✓ (was hardcoded, now from config) | Regression fixed |
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| SuperTonic | Ignores | Ignores | No change — no language concept |
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| Future plugins | May read | May ignore | Field-ignoring rule applies |
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## Contract tests added
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```python
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class TestEngineConfigContract:
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def test_default_lang_code(self) # EngineConfig().lang_code == "a"
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def test_custom_lang_code(self) # EngineConfig(lang_code="j").lang_code == "j"
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def test_immutability_lang_code(self) # frozen — cannot reassign
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def test_plugins_may_ignore_irrelevant_fields(self) # field-ignoring rule
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def test_engine_config_contains_engine_instance_configuration(self) # definition
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```
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## Files changed
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| File | Change |
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|------|--------|
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| `abogen/tts_plugin/types.py` | Updated docstring, added `lang_code: str = "a"` |
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| `plugins/kokoro/__init__.py` | Reads `config.lang_code` instead of hardcoded `"a"` |
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| `abogen/tts_plugin/utils.py` | `create_pipeline()` passes `lang_code` to `EngineConfig` |
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| `tests/contracts/test_types_contract.py` | 5 new contract tests |
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| `tests/contracts/test_plugin_manager_contract.py` | Updated assertion for `lang_code` |
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| `tests/test_behavioral_regression.py` | Updated `test_engine_config_defaults` |
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