generate-code

Code Generation from VDM-SL Specifications

Read VDM-SL specifications (types, functions, operations, invariants) and generate TypeScript or Python implementation scaffolds. Includes runtime verification (pre/post/inv checks).

VDM-SL仕様を読み取り、TypeScript/Pythonの実装スキャフォールドを生成する。 ランタイム検証（pre/post/inv チェック）も含める。

Generation Flow

Step 1: Read the Specification File

Read the .vdmsl file specified by the user. If no file is specified, search for .vdmsl files in the workspace.

ユーザーが指定した .vdmsl ファイルを読み取る。指定がなければワークスペース内を探索。

Step 2: Confirm Target Language

If the user hasn't specified, ask with AskUserQuestion:

• TypeScript
• Python
• Both

ユーザーが明示しない場合、AskUserQuestionで確認する。

Step 3: VDM-SL → Code Conversion

Follow the conversion rules in references/typescript-rules.md or references/python-rules.md.

references/typescript-rules.md または references/python-rules.md の変換ルールに従う。

Generated file structure:

TypeScript:

generated/
├── types.ts          -- Type definitions (interface/type)
├── contracts.ts      -- Pre/post/invariant verification functions
├── <module>.ts       -- Function/operation implementation scaffolds
└── index.ts          -- Exports

Python:

generated/
├── types.py          -- Type definitions (dataclass)
├── contracts.py      -- Pre/post/invariant verification functions
├── <module>.py       -- Function/operation implementation scaffolds
└── __init__.py       -- Exports

Step 4: Type Conversion

Convert VDM-SL types to target language types. See references for detailed rules.

VDM-SL型をターゲット言語の型に変換する。変換ルールの詳細はリファレンス参照。

Core mapping:

VDM-SL	TypeScript	Python
nat, nat1, int	number	int
real	number	float
bool	boolean	bool
seq of char	string	str
seq of T	T[]	list[T]
set of T	Set<T>	set[T]
map K to V	Map<K, V>	dict[K, V]
Record type	interface	@dataclass
[T] (option)	T | null	Optional[T]
Union type	union type	Union[...]

Step 5: Generate Contract Verification Code

Generate runtime check functions for invariants, pre-conditions, and post-conditions.

不変条件・事前条件・事後条件をランタイムチェック関数として生成する。

Policy:

• Invariants → factory functions or validation functions for types
• Pre-conditions → assert/raise at function entry
• Post-conditions → assert/raise at function exit (debug mode)
• Toggle verification on/off with environment variable VDM_CONTRACT_CHECK

Step 6: Generate Function/Operation Scaffolds

Explicit definitions → convert implementation where possible Implicit definitions (pre/post only) → generate stubs with TODO comments

明示的定義 → 可能な範囲で実装を変換。暗黙的定義 → TODO付きスタブを生成。

// VDM-SL: findUser(uid, users) == users(uid) pre uid in set dom users
function findUser(uid: UserId, users: Map<UserId, User>): User {
  // Pre-condition check
  assert(users.has(uid), `Pre-condition failed: uid ${uid} not in users`);

  // Implementation
  const result = users.get(uid)!;

  return result;
}

Step 7: Output Files

Place generated code in a generated/ subfolder in the same directory as the spec file. If files already exist, ask the user for overwrite confirmation.

生成したコードを仕様ファイルと同じディレクトリの generated/ に配置する。

Generated Code Quality Guidelines

• Generated code should be immediately runnable (no compilation errors)
• Mark locations requiring manual implementation with TODO comments
• Include the original VDM-SL definition in JSDoc / docstrings
• Contract violation error messages should be specific (which condition failed, with what value)

生成コードはそのまま動作可能な状態を目指す。TODOで手動実装箇所を明示。 JSDoc/docstringで元のVDM-SL定義を記載。エラーメッセージは具体的に。

Handling Unconvertible Syntax

The following constructs cannot be generated and should be noted with TODO comments:

以下はコード生成を断念し TODO コメントで注記する:

• exists / exists1 quantifiers → describe semantics in comments
• Pattern match exhaustiveness guarantees → suggest type guards only
• Map comprehension {k |-> v | ...} → convert to loop construction or TODO
• Auto-insertion of state invariants → recommend hooks on state-changing methods

Detailed References

• references/typescript-rules.md — Complete TypeScript conversion rules
• references/python-rules.md — Complete Python conversion rules