fix(yang-push): resolve xpath-filter target modules by prefix

[rodonile]

Summary

YANG-Push cache misses that fall back to fetch-by-subscription-id failed for
devices sending an inline datastore-xpath-filter without xmlns prefix
bindings (e.g. Cisco IOS-XR, where the path prefix is the YANG module name,
like Cisco-IOS-XR-procmem-oper:...). Module resolution only consulted
declared namespace prefixes, so the subscription's own target module was
never considered for the NETCONF get-schema set.

Devices that declare xmlns bindings on their filters (e.g. Huawei) were
unaffected.

Root cause

Per RFC 8641, the XPath context for datastore-xpath-filter is built by
combining two prefix-resolution mechanisms:

1. Implicit: the prefix is the YANG module name for every module the
   server implements (no xmlns needed) — this is what Cisco IOS-XR uses.
2. Additive: xmlns declarations on the leaf element, which override on
   conflict — this is what Huawei uses.

The fetcher only supported mechanism (2), so inline Cisco filters resolved to
zero modules and the fetch "succeeded" with an incomplete library.

Changes

• Resolve xpath-filter modules per the full RFC 8641 context: try the
  declared xmlns binding first, then fall back to treating the path prefix
  as the YANG module name. Subtree and stream filters keep namespace-based
  lookup.
• Hard-fail on empty resolution instead of caching an incomplete library
  that keeps failing validation forever.
• Scope the prefix-as-module-name fallback by datastore: the implicit
  fallback now uses a datastore-scoped module lookup (mirroring the
  namespace-based one) instead of an unscoped search, so it can't return a
  module revision pinned in an unrelated datastore/module-set.
• Improved logging and added unit tests covering the two resolution paths

[Copilot]

Pull request overview

Fixes YANG-Push cache fallback by resolving inline XPath prefixes against device YANG libraries.

Changes:

• Adds namespace and module-name prefix resolution.
• Rejects empty or unresolved module sets.
• Adds diagnostics and resolution tests.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/yang-push/src/cache/storage.rs	Adds resolution-specific errors.
crates/yang-push/src/cache/fetcher.rs	Implements target-module resolution.
crates/netconf-proto/src/yang_push/tests.rs	Tests XPath prefix extraction.
crates/netconf-proto/src/yang_push/filters.rs	Exposes path prefixes.
crates/netconf-proto/src/xml_utils.rs	Shares XPath prefix parsing.
crates/netconf-proto/src/client.rs	Adds NETCONF diagnostics.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.

Suppressed comments (1)

crates/netconf-proto/src/yang_push/tests.rs:803

• The Huawei-style XPath example has a likely typo in the path (devm:chassiss). It doesn’t affect the prefix-extraction assertion, but it makes the test fixture harder to read and can confuse future debugging (it looks like it’s meant to be devm:chassis).

        namespaces: Box::new([
            ("devm".into(), "urn:huawei:yang:huawei-devm".into()),
            ("driver".into(), "urn:huawei:yang:huawei-driver".into()),
        ]),
        path: "/devm:devm/devm:chassiss/devm:chassis/driver:power-supply-attribute".into(),
    };