OTTL Playground Autocomplete Implementation Summary

[jsvd]

The implementation adds version-accurate OTTL (OpenTelemetry Transformation Language) autocomplete, validation, and IDE-like features. Features adapt automatically based on which collector version is selected.

Architecture

pkg/ottl/metadata/           # Upstream-ready metadata extraction
  metadata.go                # Core types: FunctionInfo, ParameterInfo, PathInfo, EnumInfo
  introspect.go              # Reflection-based factory introspection
  functions.go               # Function extraction from StandardFuncs registry
  contexts.go                # Context paths and enums (log, span, metric, etc.)

wasm/
  main.go                    # WASM exports for JS interop
  internal/
    metadata.go              # Bridge between pkg/ottl/metadata and WASM
    validator.go             # Native OTTL parser validation
    completion_context.go    # Lexer-based cursor context detection

web/src/components/
  ottl-completion.js         # CodeMirror 6 extensions (completion, hover, linting)
  panels/config-panel.js     # Integrates extensions, forceLint() for version changes
  playground.js              # Version switching, cache invalidation

Features

1. Autocompletion

• Function completions with parameter snippets
• Context-aware path completions (body, attributes, trace_id, etc.)
• Enum completions (SEVERITY_NUMBER_, SPAN_KIND_, etc.)
• Lexer-based context detection (handles parens inside strings, nested calls)
• Works in where clauses: set(body, x) where HasPrefix(...)
• Triggers: Cmd+., Alt+Space, or typing

2. Signature Help

• Shows function signature while typing arguments
• Highlights current parameter
• Updates as cursor moves between arguments

3. Validation/Linting

• Uses native OTTL parsers (ottllog.NewParser, etc.)
• Real-time squiggly underlines for errors
• Accurate error positioning within statements
• Context-aware (log, span, metric, datapoint, resource, scope)
• Auto re-validates when version changes

4. Hover Documentation

• Function hover: signature, parameters, editor vs converter
• Path hover: type, description, key support
• Enum hover: name and numeric value

5. Go-to-Definition

• Cmd/Ctrl+Click on function names
• Opens OTTL documentation on GitHub

Version Accuracy

All metadata extracted at WASM compile time via reflection:

// pkg/ottl/metadata/functions.go
func ExtractStandardFunctions[K any]() []FunctionInfo {
    factories := ottlfuncs.StandardFuncs[K]()  // Version-specific!
    return ExtractAndSortFunctions(factories)
}

WASM Exports

window.getOTTLFunctions()           // All functions with parameters
window.getContextPaths(context)     // Paths for log/span/metric/etc.
window.getContextEnums(context)     // Enums for the context
window.getOTTLMetadata()            // Complete metadata bundle
window.validateStatements(config, dataType, payload, executor)
window.getCompletionContext(stmt)   // Lexer-based cursor context

Multi-Version Support

Version	Functions	Size (raw)	Size (gzip)
v0.138.0	92	55MB	~10MB
v0.125.0	82	52MB	~9MB

When switching versions:

1. New WASM binary loads
2. Metadata cache cleared
3. Editor re-lints with new validator
4. Completions reflect exact version capabilities

Build

# Build WASM for specific version
PROCESSORS_VERSION=v0.138.0 make build-wasm

# Build uses -trimpath for smaller binaries
cd wasm; GOARCH=wasm GOOS=js go build -trimpath -ldflags "-s -w" ...