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Cross-language code meta-model library using unified MetaAST representation. Parse, transform, and translate code across Python, Elixir, Ruby, Erlang, Haskell, and more via a shared three-tuple AST format.
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lib/metastatic/adapters/python/subprocess.ex
defmodule Metastatic.Adapters.Python.Subprocess do
@moduledoc """
Subprocess management for Python parser and unparser.
Handles communication with Python scripts via stdin/stdout with JSON serialization.
"""
@parser_path "priv/parsers/python/parser.py"
@unparser_path "priv/parsers/python/unparser.py"
@doc """
Parse Python source code to AST JSON.
## Examples
iex> Metastatic.Adapters.Python.Subprocess.parse("x + 5")
{:ok, %{"_type" => "Module", "body" => [...]}}
iex> Metastatic.Adapters.Python.Subprocess.parse("x +")
{:error, "SyntaxError: ..."}
"""
@spec parse(String.t()) :: {:ok, map()} | {:error, String.t()}
def parse(source) do
case run_python_script(@parser_path, source) do
{:ok, result} ->
case Jason.decode(result) do
{:ok, %{"ok" => true, "ast" => ast}} ->
{:ok, ast}
{:ok, %{"ok" => false, "error" => error}} ->
{:error, format_error(error)}
{:error, reason} ->
{:error, "JSON decode failed: #{inspect(reason)}"}
end
{:error, reason} ->
{:error, "Python process failed: #{inspect(reason)}"}
end
end
@doc """
Unparse AST JSON back to Python source code.
## Examples
iex> ast = %{"_type" => "Module", "body" => [...]}
iex> Metastatic.Adapters.Python.Subprocess.unparse(ast)
{:ok, "x + 5"}
"""
@spec unparse(map()) :: {:ok, String.t()} | {:error, String.t()}
def unparse(ast) do
case Jason.encode(ast) do
{:ok, json} ->
case run_python_script(@unparser_path, json) do
{:ok, result} ->
case Jason.decode(result) do
{:ok, %{"ok" => true, "source" => source}} ->
{:ok, source}
{:ok, %{"ok" => false, "error" => error}} ->
{:error, format_error(error)}
{:error, reason} ->
{:error, "JSON decode failed: #{inspect(reason)}"}
end
{:error, reason} ->
{:error, "Python process failed: #{inspect(reason)}"}
end
{:error, reason} ->
{:error, "JSON encode failed: #{inspect(reason)}"}
end
end
# Private Functions
defp run_python_script(script_path, input) do
script_full_path = Path.join(File.cwd!(), script_path)
# Check if script exists
if File.exists?(script_full_path) do
# Use printf to pipe input to python3
# This avoids stdin: option which doesn't exist in System.cmd
case System.cmd("sh", [
"-c",
"printf '%s' #{shell_escape(input)} | python3 #{script_full_path}"
]) do
{output, 0} ->
{:ok, output}
{error_output, exit_code} ->
{:error, "Exit code #{exit_code}: #{error_output}"}
end
else
{:error, "Python script not found: #{script_full_path}"}
end
rescue
e ->
{:error, "Exception: #{Exception.message(e)}"}
end
defp format_error(%{"type" => type, "msg" => msg, "lineno" => line}) do
"#{type} at line #{line}: #{msg}"
end
defp format_error(%{"type" => type, "msg" => msg}) do
"#{type}: #{msg}"
end
defp format_error(error) when is_binary(error) do
error
end
defp format_error(error) do
inspect(error)
end
defp shell_escape(string) do
# Escape single quotes for shell
escaped = String.replace(string, "'", "'\\''")
"'#{escaped}'"
end
end