struct-frame-ls

VSCode Language Server for struct-frame (.sf files)

Features

• Syntax Highlighting — Full highlighting for messages, enums, primitive types, keywords, comments, field options, and string literals
• Go-to-Definition — Click on a message or enum type name to jump to its definition, including across imported files
• Autocomplete — Context-aware suggestions:
  • Top-level keywords (message, enum, package, import, option, repeated, oneof)
  • Field types: all primitive types plus user-defined messages and enums from the current file and its imports
  • Inside [...]: field option names (size=, max_size=, element_size=, flatten=, default=)
  • After option: context-aware option names (msgid, pkgid, variable, magic_bytes, extensions_start, and oneof options)
• Hover Documentation — Hover over a type name to see its definition summary or a description of the primitive type
• Document Symbols / Outline — All messages and enums listed in the outline with their fields and enum values

struct-frame Syntax

struct-frame uses a protobuf-like syntax with .sf file extension:

package sensor_data;

option pkgid = 1;

enum SensorStatus {
  OFFLINE = 0;
  ONLINE  = 1;
  ERROR   = 2;
}

message SensorReading {
  option msgid = 1;
  option variable = true;
  option magic_bytes = "0xA3, 0x7F";

  SensorStatus status    = 1 [default=ONLINE];
  float        value     = 2 [default=0.0];
  string       name      = 3 [size=16, default="unknown"];
  repeated uint8 data    = 4 [max_size=200];
  uint32       timestamp = 5;
}

message Container {
  option msgid = 2;
  option variable = true;
  SensorReading reading = 1;

  oneof payload {
    option variable = true;
    SensorReading sensor = 1;
    SensorReading other = 2;
  }
}

Primitive types: int8, int16, int32, int64, uint8, uint16, uint32, uint64, float, double, bool, string

Field options (in [...]): size, max_size, element_size, flatten, default

Message options: msgid, variable, is_envelope, magic_bytes, extensions_start

Oneof options: discriminator, variable, max_size, min_size, extensions_start

Default values

default is an initialization and decode-fallback value. It does not change wire layout, field size, or magic bytes. It is supported for integer types, bool, float, double, enum members, and fixed or bounded strings:

enum State { IDLE = 0; READY = 1; }

message Defaults {
  State state = 1 [default=READY];
  bool enabled = 2 [default=true];
  string label = 3 [size=16, default="ready"];
}

Defaults are not supported on repeated fields, message-typed fields, or fields inside a oneof.

Diagnostics

The language server validates duplicate and unknown field options, default values and their type ranges, magic-byte format, extension anchors, field-number gaps/duplicates, oneof size rules, and oneof variant fields. Unknown option names are warnings for forward compatibility.

Development

npm install
cd client && npm install
cd ../server && npm install
cd ..
npm run compile

Open the project in VSCode and press F5 to launch the Extension Development Host.