vyper-compiler

Development

Vyper smart contract compiler internals. Use when working on the Vyper compiler codebase — compilation pipeline, Venom IR, semantic analysis, code generation, testing, or contributing. Triggers on vyper compiler development, Venom passes, AST/semantics changes, codegen work, or test writing.

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Vyper Compiler

Pythonic smart contract language targeting the EVM. v0.4.x, Python 3.11+.

Quick Commands

uv sync                                 # install deps (per-worktree .venv, recommended, includes dev group)
uv run vyper contract.vy                # compile a contract
uv run vyper -f ir_runtime contract.vy  # inspect Venom IR
uv run vyper -f asm contract.vy         # inspect assembly
uv run ./quicktest.sh                   # run tests (`-nauto -m "not fuzzing"` by default via setup.cfg)
uv run make lint                        # enforces code style (same as CI)

Prefix all commands with uv run — it activates the local .venv per invocation, which is necessary in non-interactive shells. Each worktree gets its own .venv, so no cross-contamination.

Alternative: pip install . --group dev + PYTHONPATH=. prefix on every command. Never pip install -e . — it creates an egg-link in site-packages that permanently points the venv at one worktree, breaking all others.

Compilation Pipeline

Source (.vy)
  │
  ├─ vyper/ast/            → Parse to AST (pre_parser → Python AST → Vyper AST)
  ├─ vyper/semantics/      → Type check, validate, annotate AST
  ├─ vyper/codegen/        → AST → s-expr IR (default production pipeline)
  ├─ vyper/ir/             → s-expr IR → assembly → bytecode
  └─ vyper/evm/            → Assembly → bytecode

Experimental Venom path (--experimental-codegen):

  ├─ vyper/codegen_venom/  → AST → Venom SSA IR
  └─ vyper/venom/          → Venom IR optimization passes → assembly

Orchestrated by vyper/compiler/phases.py (CompilerData). Each phase is lazy.

Directory Map

Directory	Purpose
`vyper/ast/`	Parsing, AST nodes, pre-parser. See AST README
`vyper/semantics/`	Type system, analysis, validation. See Semantics README
`vyper/codegen/`	AST → s-expr IR (default production pipeline)
`vyper/ir/`	s-expr IR → assembly → bytecode. See IR README
`vyper/codegen_venom/`	AST → Venom IR (experimental, `--experimental-codegen`)
`vyper/venom/`	Venom SSA IR: passes, analysis, assembly emission. See Venom README
`vyper/compiler/`	Pipeline orchestration, settings, output formats. See Compiler README
`vyper/builtins/`	Built-in functions and interfaces
`vyper/evm/`	EVM opcodes, assembler
`vyper/cli/`	CLI entry points (`vyper`, `vyper-ir`, `venom`)
`tests/unit/`	Unit tests (ast, semantics, compiler, venom)
`tests/functional/`	Functional tests (builtins, codegen, grammar, syntax, venom)

Topic Deep-Dives

Venom IR — SSA IR design, passes, optimization, working with Venom code
Semantics & Frontend — Type system, analysis phases, namespace, validation
Code Generation — Legacy IR, Venom codegen, the two pipelines
Testing — Test structure, fixtures, running tests, writing new tests
Contributing — Commit message standards, PR workflow, code style summary

Code Style

Enforced by make lint (also what CI runs). Includes black, flake8, isort, mypy.

Line length: 100
No inline imports; standard library → third-party → local
snake_case for variables (tmp = ...), DromedaryCase (aka upper camelCase) for classes (ExprAnalyzer), type classes end in T (e.g. IntegerT, ModuleT)

Key Entry Points

What	Where
Main compile function	`vyper.compiler.compile_code()`
Pipeline phases	`vyper.compiler.phases.CompilerData`
AST parsing	`vyper.ast.parse.parse_to_ast()`
Semantic analysis	`vyper.semantics.analyze_module()`
Legacy codegen	`vyper.codegen.module`
AST → Venom IR	`vyper.codegen_venom.module`
Venom → assembly	`vyper.venom.generate_assembly_experimental()`
CLI entry	`vyper.cli.vyper_compile`