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80 lines
2.1 KiB
Markdown
80 lines
2.1 KiB
Markdown
---
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name: runtime-sink-file-path-or-none
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group: api
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category: runtime
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update-time: 20260707
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description: Read the effective file path from a RuntimeSink only when it is actually file-backed.
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key-word:
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- runtime
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- sink
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- file
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- truthful
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---
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## Runtime-sink-file-path-or-none
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Read the effective file path from a `RuntimeSink` only when it is actually file-backed.
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This is the truthful companion to `file_path()`. Prefer it for diagnostics, branching, and recovery logic that must distinguish “not file-backed” from compatibility fallbacks.
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### Interface
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```moonbit
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pub fn RuntimeSink::file_path_or_none(self : RuntimeSink) -> String? {
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```
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#### input
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- `self : RuntimeSink` - Runtime sink whose file path should be inspected.
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#### output
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- `String?` - `Some(path)` when the runtime sink is file-backed, otherwise `None`.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- Plain `File` runtime variants return `Some(path)`.
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- `QueuedFile` runtime variants forward the wrapped inner file sink path as `Some(path)`.
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- Non-file runtime variants return `None`.
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- This helper is observation-only and does not mutate runtime state.
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### How to Use
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Here are some specific examples provided.
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#### When Need Truthful File-backed Detection
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When code should branch only if file semantics really exist:
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```moonbit
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match sink.file_path_or_none() {
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Some(path) => println(path)
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None => ()
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}
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```
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In this example, `None` means the runtime sink is not file-backed.
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#### When Need Path Diagnostics Without Fallback Values
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When support output should avoid compatibility placeholders:
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```moonbit
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let maybe_path = sink.file_path_or_none()
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```
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In this example, callers can keep “no file semantics” distinct from a real path.
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### Error Case
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e.g.:
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- If the runtime sink is not file-backed, the method returns `None`.
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- If callers need the broader file snapshot or queue context, prefer `file_state_or_none()` or `file_runtime_state()`.
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### Notes
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1. Prefer this helper over `file_path()` for truthful runtime diagnostics.
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2. `file_path()` remains available as the compatibility fallback API.
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