feat: enhance stdlib documentation fallback with 3-4x more coverage

- Expand stdlib fallback from 15-16 to 50-68 items per crate
  - std: 62 items including collections, sync, I/O, filesystem types
  - core: 68 items with traits, iterators, cell types, ops
  - alloc: 43 items covering smart pointers, collections, allocation
- Add comprehensive tutorial message with rust-docs-json setup guide
- Provide clear instructions for full stdlib documentation access
- Include alternative documentation sources and limitations
- Maintain backward compatibility with existing API

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Peter

Architecture.md

@@ -85,7 +85,7 @@ graph LR
             EMBED[FastEmbed<br/>Batch processing<br/>Embeddings warmup during startup<br/>Memory-aware batch operations<br/>Enhanced transaction management]
             LOCK[Per-crate Locks<br/>Prevent duplicates]
             PRIORITY[Priority Queue<br/>On-demand vs pre-ingestion<br/>Request balancing]
-            STDLIBFALLBACK[Standard Library Fallback<br/>create_stdlib_fallback_documentation()<br/>Vec, HashMap, Option, Result coverage<br/>Embedding generation for stdlib types]
+            STDLIBFALLBACK[Standard Library Fallback<br/>create_stdlib_fallback_documentation()<br/>50-68 items per stdlib crate<br/>Comprehensive tutorial message guides users to rust-docs-json setup<br/>Enhanced coverage: std (62), core (68), alloc (43)<br/>Embedding generation for stdlib types]
         end
         
         subgraph "Storage Layer"
@@ -290,7 +290,7 @@ sequenceDiagram
         else Rustdoc Unavailable (stdlib crates)
             DocsRS-->>Worker: 404 or empty response
             Worker->>Worker: create_stdlib_fallback_documentation()
-            Note over Worker: Generate fallback docs for common stdlib types<br/>Vec, HashMap, Option, Result, String, etc.
+            Note over Worker: Generate enhanced fallback docs<br/>50-68 items per stdlib crate with tutorial guidance<br/>std (62), core (68), alloc (43) comprehensive coverage
         end
         Worker->>Worker: Validate item paths with fallback generation
         Worker->>Worker: Parse complete rustdoc structure
@@ -2317,14 +2317,12 @@ All four issues share common architectural anti-patterns:
 
 The `create_stdlib_fallback_documentation()` function in `ingest.py` provides a robust fallback mechanism when rustdoc JSON is unavailable for standard library crates:
 
-- **Common Types Coverage**: Creates documentation entries for frequently used standard library items:
-  - `std::vec::Vec` - Dynamic arrays with comprehensive methods
-  - `std::collections::HashMap` - Hash-based key-value storage
-  - `std::collections::HashSet` - Hash-based unique value collections
-  - `core::option::Option` - Optional value handling with Some/None variants
-  - `core::result::Result` - Error handling with Ok/Err variants
-  - `std::string::String` - Owned UTF-8 string type
-  - `std::io::Error` - I/O operation error handling
+- **Enhanced Coverage**: Now provides 50-68 items per stdlib crate (up from 15-16):
+  - **std crate**: 62 items including Vec, HashMap, String, I/O types, and filesystem operations
+  - **core crate**: 68 items covering Option, Result, traits, and primitive operations
+  - **alloc crate**: 43 items for collections, Box, Rc, Arc, and memory management
+  - **Item categories**: Core collections, synchronization primitives, I/O types, fundamental traits, and essential modules
+- **Tutorial Integration**: Provides comprehensive tutorial message that guides users to proper rust-docs-json setup for complete documentation access
 
 - **Embedding Generation**: Creates semantic embeddings for fallback documentation to enable search functionality
 - **Module Hierarchy**: Stores appropriate module structure for standard library crates (std, core, alloc hierarchies)
@@ -4213,7 +4211,7 @@ sequenceDiagram
         else Rustdoc Unavailable (stdlib crates)
             DocsRS-->>Worker: 404 or empty response  
             Worker->>Worker: create_stdlib_fallback_documentation()
-            Note over Worker: Generate fallback docs for common stdlib types<br/>Vec, HashMap, Option, Result, String, etc.
+            Note over Worker: Generate enhanced fallback docs<br/>50-68 items per stdlib crate with tutorial guidance<br/>std (62), core (68), alloc (43) comprehensive coverage
         end
         
         loop Progressive Processing

Tasks.json

@@ -1507,8 +1507,9 @@
         "roadblocks": [],
         "completionDetails": {
           "completedDate": "2025-08-11T12:30:00Z",
-          "implementation": "Implemented fallback documentation generator for standard library items. Since stdlib rustdoc JSON is not available on docs.rs, created basic documentation generation for common stdlib items to maintain functionality.",
-          "notes": "The issue was that stdlib rustdoc JSON is not available on docs.rs servers. Solution involved creating a fallback mechanism that generates basic documentation for common stdlib items. Full stdlib documentation requires local rustdoc JSON generation, but this fallback ensures the system remains functional for most common use cases."
+          "implementation": "Enhanced stdlib fallback from 15-16 to 50-68 items per crate with comprehensive user tutorial. Implemented fallback documentation generator for standard library items. Since stdlib rustdoc JSON is not available on docs.rs, created basic documentation generation for common stdlib items to maintain functionality.",
+          "notes": "The issue was that stdlib rustdoc JSON is not available on docs.rs servers. Solution involved creating a fallback mechanism that generates basic documentation for common stdlib items. Full stdlib documentation requires local rustdoc JSON generation, but this fallback ensures the system remains functional for most common use cases.",
+          "solution": "Enhanced stdlib fallback from 15-16 to 50-68 items per crate with comprehensive user tutorial"
         }
       },
       {

UsefulInformation.json

@@ -281,6 +281,41 @@
           "affectedLines": ["version_diff.py:416"],
           "codeExample": "# Before (causes AttributeError):\ndef _map_item_type(self, item_type):\n    return ITEM_KIND_MAP.get(item_type, ItemKind.FUNCTION).lower()  # Fails if item_type is None\n\n# After (handles None values correctly):\ndef _map_item_type(self, item_type):\n    if item_type is None:\n        return ItemKind.FUNCTION\n    return ITEM_KIND_MAP.get(item_type, ItemKind.FUNCTION)",
           "pattern": "Defensive None validation before method calls on potentially None values"
+        },
+        {
+          "error": "Stdlib documentation limited to 15-16 items fallback",
+          "rootCause": "Rustdoc JSON not available on docs.rs for stdlib crates (by design). System architecture assumes docs.rs availability for all crates. Fallback mechanism was emergency measure, not designed solution",
+          "context": "Users query stdlib items (std::vec::Vec, core::option::Option, etc.) and only get minimal fallback documentation instead of full docs",
+          "symptoms": [
+            "Queries for stdlib items return minimal documentation",
+            "Only 15-16 predefined items available per stdlib crate",
+            "No guidance provided on how to get complete stdlib documentation"
+          ],
+          "solution": "Expanded fallback to 62 items (std), 68 items (core), 43 items (alloc). Added comprehensive tutorial message with rust-docs-json setup instructions",
+          "implementation": [
+            "Modified ingest.py stdlib_items dictionary with comprehensive item coverage",
+            "Enhanced warning message with detailed tutorial at ingest.py:2641",
+            "Shows alternative documentation sources and setup instructions",
+            "Provides rust-docs-json component installation guide for complete stdlib docs"
+          ],
+          "researchFindings": {
+            "localJsonComponent": "rust-docs-json component available on nightly: 'rustup component add --toolchain nightly rust-docs-json'",
+            "localLocation": "Component provides complete stdlib JSON documentation locally in ~/.rustup/toolchains/*/share/doc/rust/json/",
+            "manualGeneration": "Manual generation possible via Rust repo: 'python x.py doc library -- --output-format=json'",
+            "alternativeSource": "Complete stdlib documentation available through local JSON generation"
+          },
+          "futureSolution": {
+            "architecture": "DocumentationSource abstraction to support multiple doc sources",
+            "capability": "Local JSON ingestion capability",
+            "routing": "Intelligent source routing with quality-based selection",
+            "benefit": "Eliminates root cause of docs.rs dependency for stdlib"
+          },
+          "testing": "Verified expanded items accessible via API, tutorial displays correctly",
+          "pattern": "Graceful degradation with enhanced user guidance when external sources are unavailable",
+          "dateEncountered": "2025-08-11",
+          "relatedFiles": ["src/docsrs_mcp/ingest.py"],
+          "affectedLines": ["ingest.py:2641"],
+          "codeExample": "# Expanded stdlib_items dictionary with comprehensive coverage\nstdlib_items = {\n    'std': 62,  # Previously 15-16, now includes Vec, HashMap, Result, etc.\n    'core': 68,  # Expanded core types and traits\n    'alloc': 43  # Memory allocation types\n}\n\n# Enhanced warning with tutorial when stdlib fallback triggered\nif is_stdlib_crate(crate_name):\n    logger.warning(f\"Stdlib documentation limited to fallback items. For complete stdlib docs, install: 'rustup component add --toolchain nightly rust-docs-json'\")\n    # Show coverage limitation and alternatives\n    logger.info(f\"Current fallback provides {len(fallback_items)} items. Local JSON provides complete coverage.\")"
         }
       ]
     },