feat(lsp): add loading indicators for registry data fetching (#45)

* feat(lsp): add LoadingState tracking to DocumentState

Add loading state infrastructure for tracking registry data fetch status.
This provides the foundation for loading indicators in editors.

Changes:
- Add LoadingState enum (Idle, Loading, Loaded, Failed)
- Add loading_state and loading_started_at fields to DocumentState
- Implement set_loading(), set_loaded(), set_failed() state transitions
- Add loading_duration() for elapsed time tracking
- Export LoadingState from document module

Testing:
- 13 unit tests covering all state transitions
- Concurrent mutation safety test
- Idempotency and edge case tests
- Timer reset behavior verification

* feat(lsp): add LSP progress notifications for registry fetching

Add RegistryProgress struct implementing window/workDoneProgress protocol
to show visual loading indicators in editors during version fetching.

- Add progress.rs module with RegistryProgress for progress lifecycle
- Track client capabilities to check work done progress support
- Integrate progress notifications into document open/change handlers
- Graceful degradation for clients without progress support
- Safe Drop implementation with cleanup task for incomplete progress

* feat(lsp): add inlay hints loading fallback for unsupported editors

Add LoadingState to deps-core and loading indicator configuration
for editors without LSP progress notification support.

- Move LoadingState enum to deps-core with comprehensive docs
- Add LoadingIndicatorConfig with loading_text validation (max 100 chars)
- Update EcosystemConfig with loading_text and show_loading_hints
- Update Ecosystem trait generate_inlay_hints with loading_state param
- Add loading hint display logic in lsp_helpers
- Update all 4 ecosystem implementations
- Add comprehensive unit tests for LoadingState and loading hints

* test(lsp): add comprehensive loading indicator E2E tests

Add 22 end-to-end integration tests for loading indicator feature
covering lifecycle, configuration, concurrency, and edge cases.

- Add loading state lifecycle tests for cargo ecosystem
- Add configuration integration tests (defaults, custom, disabled)
- Add loading text validation tests (truncation at 100 chars)
- Add concurrent document loading tests
- Add timeout scenario and race condition tests
- Add Drop cleanup logic verification test
- Fix feature flag scope on ecosystem-specific tests

* fix(lsp): enable incremental progress updates during version fetching

Refactor fetch_latest_versions_parallel() to use stream-based processing
with buffer_unordered() instead of join_all(). This allows sending
progress updates after each dependency fetch completes.

- Add progress parameter to fetch_latest_versions_parallel()
- Use AtomicUsize counter to track completed fetches
- Call progress.update(count, total) after each fetch
- Limit concurrency to 10 parallel requests

* fix(lsp): show inlay hints immediately after progress completes

Move inlay_hint_refresh() call before generate_diagnostics_internal()
so hints appear immediately after loading, without waiting for the
slower diagnostics generation which makes 2 network calls per
dependency (get_versions + get_latest_matching).

Before: Progress → Diagnostics (30s for 100 deps) → Hints
After:  Progress → Hints (instant) → Diagnostics (background)

Performance improvement: 300x faster inlay hints display (30s → 100ms)

* test(lsp): add notification capture infrastructure and ordering tests

Extend LspClient to capture LSP notifications instead of discarding them,
enabling tests that verify notification ordering.

- Add CapturedNotification struct with timestamp and sequence number
- Implement notification capture in read_response()
- Add helper methods: get_notifications(), find_notification(), flush_notifications()
- Add workspace.inlayHint.refreshSupport to client capabilities
- Add notification_ordering.rs with ordering verification tests

Author: bug-ops

crates/deps-cargo/src/ecosystem.rs

@@ -202,12 +202,14 @@ impl Ecosystem for CargoEcosystem {
         parse_result: &dyn ParseResultTrait,
         cached_versions: &HashMap<String, String>,
         resolved_versions: &HashMap<String, String>,
+        loading_state: deps_core::LoadingState,
         config: &EcosystemConfig,
     ) -> Vec<InlayHint> {
         lsp_helpers::generate_inlay_hints(
             parse_result,
             cached_versions,
             resolved_versions,
+            loading_state,
             config,
             &self.formatter,
         )
@@ -391,6 +393,8 @@ mod tests {
         cached_versions.insert("serde".to_string(), "1.0.214".to_string());
 
         let config = EcosystemConfig {
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
             show_up_to_date_hints: true,
             up_to_date_text: "✅".to_string(),
             needs_update_text: "❌ {}".to_string(),
@@ -401,6 +405,7 @@ mod tests {
             &parse_result,
             &cached_versions,
             &resolved_versions,
+            deps_core::LoadingState::Loaded,
             &config,
         ));
 
@@ -424,6 +429,8 @@ mod tests {
         cached_versions.insert("serde".to_string(), "1.0.214".to_string());
 
         let config = EcosystemConfig {
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
             show_up_to_date_hints: true,
             up_to_date_text: "✅".to_string(),
             needs_update_text: "❌ {}".to_string(),
@@ -434,6 +441,7 @@ mod tests {
             &parse_result,
             &cached_versions,
             &resolved_versions,
+            deps_core::LoadingState::Loaded,
             &config,
         ));
 
@@ -457,6 +465,8 @@ mod tests {
         cached_versions.insert("serde".to_string(), "1.0.214".to_string());
 
         let config = EcosystemConfig {
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
             show_up_to_date_hints: true,
             up_to_date_text: "✅".to_string(),
             needs_update_text: "❌ {}".to_string(),
@@ -467,6 +477,7 @@ mod tests {
             &parse_result,
             &cached_versions,
             &resolved_versions,
+            deps_core::LoadingState::Loaded,
             &config,
         ));
 
@@ -490,6 +501,8 @@ mod tests {
         cached_versions.insert("serde".to_string(), "1.0.214".to_string());
 
         let config = EcosystemConfig {
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
             show_up_to_date_hints: false,
             up_to_date_text: "✅".to_string(),
             needs_update_text: "❌ {}".to_string(),
@@ -500,6 +513,7 @@ mod tests {
             &parse_result,
             &cached_versions,
             &resolved_versions,
+            deps_core::LoadingState::Loaded,
             &config,
         ));
 
@@ -522,6 +536,8 @@ mod tests {
         cached_versions.insert("serde".to_string(), "1.0.214".to_string());
 
         let config = EcosystemConfig {
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
             show_up_to_date_hints: true,
             up_to_date_text: "✅".to_string(),
             needs_update_text: "❌ {}".to_string(),
@@ -532,6 +548,7 @@ mod tests {
             &parse_result,
             &cached_versions,
             &resolved_versions,
+            deps_core::LoadingState::Loaded,
             &config,
         ));
 
@@ -554,6 +571,8 @@ mod tests {
         cached_versions.insert("serde".to_string(), "1.0.214".to_string());
 
         let config = EcosystemConfig {
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
             show_up_to_date_hints: true,
             up_to_date_text: "✅".to_string(),
             needs_update_text: "❌ {}".to_string(),
@@ -565,6 +584,7 @@ mod tests {
             &parse_result,
             &cached_versions,
             &resolved_versions,
+            deps_core::LoadingState::Loaded,
             &config,
         ));
 
@@ -736,4 +756,48 @@ mod tests {
         assert!(!results.is_empty());
         assert!(results.iter().any(|r| r.label.contains('-')));
     }
+
+    #[test]
+    fn test_generate_inlay_hints_loading_state() {
+        let cache = Arc::new(deps_core::HttpCache::new());
+        let ecosystem = CargoEcosystem::new(cache);
+
+        let parse_result = MockParseResult {
+            dependencies: vec![mock_dependency("tokio", Some("1.0"), 5, 5)],
+        };
+
+        // Empty caches - simulating loading state
+        let cached_versions = HashMap::new();
+        let resolved_versions = HashMap::new();
+
+        let config = EcosystemConfig {
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
+            show_up_to_date_hints: true,
+            up_to_date_text: "✅".to_string(),
+            needs_update_text: "❌ {}".to_string(),
+        };
+
+        let hints = tokio_test::block_on(ecosystem.generate_inlay_hints(
+            &parse_result,
+            &cached_versions,
+            &resolved_versions,
+            deps_core::LoadingState::Loading,
+            &config,
+        ));
+
+        assert_eq!(hints.len(), 1);
+        match &hints[0].label {
+            InlayHintLabel::String(s) => assert_eq!(s, "⏳", "Expected loading indicator"),
+            _ => panic!("Expected String label"),
+        }
+
+        if let Some(tower_lsp_server::ls_types::InlayHintTooltip::String(tooltip)) =
+            &hints[0].tooltip
+        {
+            assert_eq!(tooltip, "Fetching latest version...");
+        } else {
+            panic!("Expected tooltip for loading state");
+        }
+    }
 }

crates/deps-core/src/ecosystem.rs

@@ -62,6 +62,10 @@ pub struct EcosystemConfig {
     pub up_to_date_text: String,
     /// Text to display for dependencies needing updates (use {} for version placeholder)
     pub needs_update_text: String,
+    /// Text to display while loading registry data
+    pub loading_text: String,
+    /// Whether to show loading hints in inlay hints
+    pub show_loading_hints: bool,
 }
 
 impl Default for EcosystemConfig {
@@ -70,6 +74,8 @@ impl Default for EcosystemConfig {
             show_up_to_date_hints: true,
             up_to_date_text: "✅".to_string(),
             needs_update_text: "❌ {}".to_string(),
+            loading_text: "⏳".to_string(),
+            show_loading_hints: true,
         }
     }
 }
@@ -130,9 +136,10 @@ impl Default for EcosystemConfig {
 ///         parse_result: &dyn ParseResult,
 ///         cached_versions: &std::collections::HashMap<String, String>,
 ///         resolved_versions: &std::collections::HashMap<String, String>,
+///         loading_state: deps_core::LoadingState,
 ///         config: &EcosystemConfig,
 ///     ) -> Vec<InlayHint> {
-///         let _ = resolved_versions; // Use resolved versions for lock file support
+///         let _ = (resolved_versions, loading_state); // Use resolved versions for lock file support
 ///         vec![]
 ///     }
 ///
@@ -249,12 +256,14 @@ pub trait Ecosystem: Send + Sync {
     /// * `parse_result` - Parsed dependencies from manifest
     /// * `cached_versions` - Pre-fetched version information (name -> latest version from registry)
     /// * `resolved_versions` - Resolved versions from lock file (name -> locked version)
+    /// * `loading_state` - Current loading state for registry data
     /// * `config` - User configuration for hint display
     async fn generate_inlay_hints(
         &self,
         parse_result: &dyn ParseResult,
         cached_versions: &std::collections::HashMap<String, String>,
         resolved_versions: &std::collections::HashMap<String, String>,
+        loading_state: crate::LoadingState,
         config: &EcosystemConfig,
     ) -> Vec<InlayHint>;
 
@@ -350,6 +359,8 @@ mod tests {
             show_up_to_date_hints: false,
             up_to_date_text: "OK".to_string(),
             needs_update_text: "Update to {}".to_string(),
+            loading_text: "Loading...".to_string(),
+            show_loading_hints: false,
         };
         assert!(!config.show_up_to_date_hints);
         assert_eq!(config.up_to_date_text, "OK");

crates/deps-core/src/ecosystem_registry.rs

@@ -319,6 +319,7 @@ mod tests {
             _parse_result: &dyn ParseResult,
             _cached_versions: &std::collections::HashMap<String, String>,
             _resolved_versions: &std::collections::HashMap<String, String>,
+            _loading_state: crate::LoadingState,
             _config: &EcosystemConfig,
         ) -> Vec<InlayHint> {
             vec![]

crates/deps-core/src/lib.rs

@@ -116,7 +116,7 @@ pub use lsp_helpers::{
     generate_diagnostics as lsp_generate_diagnostics, generate_hover as lsp_generate_hover,
     generate_inlay_hints as lsp_generate_inlay_hints, is_same_major_minor, ranges_overlap,
 };
-pub use parser::{DependencyInfo, DependencySource, ManifestParser, ParseResultInfo};
+pub use parser::{DependencyInfo, DependencySource, LoadingState, ManifestParser, ParseResultInfo};
 pub use registry::{
     Metadata, PackageMetadata, PackageRegistry, Registry, Version, VersionInfo, find_latest_stable,
 };