openscad-parser 2.6.1

A PEG parser to read OpenSCAD language source code, with optional AST tree generation.

A PEG parser for the OpenSCAD language that can parse OpenSCAD source code and optionally generate an Abstract Syntax Tree (AST) for programmatic analysis and manipulation.

Features

• Full OpenSCAD language support including: - Module and function definitions - Expressions with proper operator precedence - Control structures (if/else, for loops, let, assert, echo) - List comprehensions - Module modifiers (!, #, %, *) - Use and include statements

• Parse tree generation using Arpeggio PEG parser

• AST generation with comprehensive node types

• Source position tracking for all AST nodes

• AST tree can contain comment nodes (single-line and multi-line)

• AST tree uses dataclasses and can be pickled/unpickled for caching/serialization

• JSON and YAML serialization/deserialization of AST trees

• Pretty-printer that converts an AST back to formatted OpenSCAD source (to_openscad()) with correct operator-precedence parenthesization

• Command-line interface (openscad-parser) for JSON/YAML/formatted output

Installation

Install from PyPI:

pip install openscad-parser

Or install from source:

git clone https://github.com/belfryscad/openscad_parser.git
cd openscad_parser
pip install -e .

Basic Usage

Parsing OpenSCAD Code

To parse OpenSCAD code, first create a parser instance, then parse your code:

from openscad_parser import getOpenSCADParser

# Create a parser instance
parser = getOpenSCADParser(reduce_tree=False)

# Parse OpenSCAD code
code = """
module test(x, y=10) {
    cube([x, y, 5]);
    translate([0, 0, y]) sphere(5);
}
"""

parse_tree = parser.parse(code)

The parser returns an Arpeggio parse tree that represents the structure of your OpenSCAD code.

Parser Options

The getOpenSCADParser() function accepts several options:

parser = getOpenSCADParser(
    reduce_tree=False,  # Keep full parse tree (default: False)
    debug=False         # Enable debug output (default: False)
)

• reduce_tree: If True, reduces the parse tree by removing single-child nodes. Set to False when generating ASTs.

• debug: If True, enables verbose debug output during parsing.

AST Generation

The parser can convert the parse tree into an Abstract Syntax Tree (AST) with typed nodes for easier programmatic manipulation.

Convenience Functions

The easiest way to generate ASTs is using the convenience functions that handle parser creation automatically:

Parsing from a String

Use getASTfromString() to parse OpenSCAD code from a string:

from openscad_parser.ast import getASTfromString

code = "x = 10 + 5;"
ast = getASTfromString(code)

# ast is a list of top-level statements
assignment = ast[0]
print(assignment.name.name)  # "x"
print(assignment.expr)         # AdditionOp(left=NumberLiteral(10), right=NumberLiteral(5))

Parsing from a File

Use getASTfromFile() to parse an OpenSCAD file. This function includes automatic caching - files are only re-parsed if their modification timestamp changes:

from openscad_parser.ast import getASTfromFile

# Parse a file (cached automatically)
ast = getASTfromFile("my_model.scad")

# Subsequent calls return cached AST if file hasn't changed
ast2 = getASTfromFile("my_model.scad")  # Returns cached version

The cache is automatically invalidated when the file is modified, ensuring you always get up-to-date results.

Include Processing: By default, getASTfromFile() processes include <file> statements before parsing (process_includes=True). This means the AST will NOT contain IncludeStatement nodes - instead, the included file contents are expanded into the AST. Set process_includes=False to preserve IncludeStatement nodes in the AST:

# Get AST with IncludeStatement nodes preserved
ast_with_includes = getASTfromFile("my_model.scad", process_includes=False)

Note: Unlike include statements, use <file> statements are ALWAYS parsed into UseStatement AST nodes, regardless of the process_includes setting. This is because use statements only affect module and function lookup at runtime, not source inclusion.

Parsing Library Files

Use getASTfromLibraryFile() to find and parse library files using OpenSCAD’s search path rules. This is useful for resolving use and include statements:

from openscad_parser.ast import getASTfromLibraryFile

# From a file that includes a library
# Searches: current file directory, OPENSCADPATH, platform defaults
# Returns: (AST, absolute_path) tuple
ast, path = getASTfromLibraryFile("/path/to/main.scad", "utils/math.scad")

# Or without current file context
ast, path = getASTfromLibraryFile("", "MCAD/boxes.scad")

The function searches for library files in this order:

1. Directory of the current file (if provided)

2. Directories in the OPENSCADPATH environment variable

3. Platform-specific default library directories: - Windows: ~/Documents/OpenSCAD/libraries - macOS: ~/Documents/OpenSCAD/libraries - Linux: ~/.local/share/OpenSCAD/libraries

Advanced AST Generation

For more control, you can use parse_ast() directly with a custom parser instance:

from openscad_parser import getOpenSCADParser
from openscad_parser.ast import parse_ast

# Create a parser instance
parser = getOpenSCADParser(reduce_tree=False)

# Parse and generate AST
code = "x = 10 + 5;"
ast = parse_ast(parser, code)

# ast is a list of top-level statements
assignment = ast[0]
print(assignment.name.name)  # "x"
print(assignment.expr)       # AdditionOp(left=NumberLiteral(10), right=NumberLiteral(5))

The parse_ast() function is the lower-level API for AST generation. It takes:

• parser: An Arpeggio parser instance (from getOpenSCADParser())

• code: The OpenSCAD code string to parse

• file: Optional file path for source location tracking

Working with AST Nodes

All AST nodes inherit from ASTNode and have a position attribute for source location tracking:

from openscad_parser.ast import (
    getASTfromString, Assignment, Identifier, NumberLiteral, AdditionOp
)

code = "result = 10 + 20;"
ast = getASTfromString(code)
assignment = ast[0]

# Check node types
assert isinstance(assignment, Assignment)
assert isinstance(assignment.name, Identifier)
assert isinstance(assignment.expr, AdditionOp)

# Access node properties
print(assignment.name.name)           # "result"
print(assignment.expr.left.val)      # 10
print(assignment.expr.right.val)      # 20

# Access source position
print(assignment.position.line)      # Line number (1-indexed)
print(assignment.position.column)    # Column number (1-indexed)

Examples

Parsing a Simple Assignment

from openscad_parser import getOpenSCADParser
from openscad_parser.ast import parse_ast, Assignment, Identifier

parser = getOpenSCADParser(reduce_tree=False)
code = "x = 42;"
ast = parse_ast(parser, code)

assignment = ast[0]
assert isinstance(assignment, Assignment)
assert assignment.name.name == "x"
assert assignment.expr.val == 42

Parsing a Module Definition

From a file:

from openscad_parser.ast import getASTfromFile, ModuleDeclaration, ModularCall

ast = getASTfromFile("box.scad")
module = ast[0]

assert isinstance(module, ModuleDeclaration)
assert module.name.name == "box"
assert len(module.parameters) == 1
assert len(module.children) == 1
assert isinstance(module.children[0], ModularCall)
assert module.children[0].name.name == "cube"

Or from a string:

from openscad_parser.ast import getASTfromString, ModuleDeclaration, ModularCall

code = """
module box(size) {
    cube(size);
}
"""

ast = getASTfromString(code)
module = ast[0]

assert isinstance(module, ModuleDeclaration)
assert module.name.name == "box"
assert len(module.parameters) == 1
assert len(module.children) == 1
assert isinstance(module.children[0], ModularCall)
assert module.children[0].name.name == "cube"

Parsing Expressions

from openscad_parser.ast import (
    getASTfromString, Assignment, AdditionOp, MultiplicationOp, NumberLiteral
)

code = "result = (10 + 5) * 2;"
ast = getASTfromString(code)

assignment = ast[0]
# The expression tree preserves operator precedence
mult_op = assignment.expr
assert isinstance(mult_op, MultiplicationOp)
assert isinstance(mult_op.left, AdditionOp)
assert mult_op.left.left.val == 10
assert mult_op.left.right.val == 5
assert mult_op.right.val == 2

Parsing Function Calls

from openscad_parser.ast import (
    getASTfromString, PrimaryCall, PositionalArgument, NamedArgument
)

code = "x = foo(1, b=2);"
ast = getASTfromString(code)

assignment = ast[0]
call = assignment.expr
assert isinstance(call, PrimaryCall)
assert call.left.name == "foo"
assert len(call.arguments) == 2
assert isinstance(call.arguments[0], PositionalArgument)
assert isinstance(call.arguments[1], NamedArgument)
assert call.arguments[1].name.name == "b"

Parsing Library Files

from openscad_parser.ast import getASTfromLibraryFile, ModuleDeclaration

# Parse a library file using OpenSCAD's search path
# Searches: current file dir, OPENSCADPATH, platform defaults
# Returns: (AST, absolute_path) tuple
ast, path = getASTfromLibraryFile("/path/to/main.scad", "utils/math.scad")

# Or without current file context
ast, path = getASTfromLibraryFile("", "MCAD/boxes.scad")

AST Node Types

The AST includes comprehensive node types for all OpenSCAD language constructs. All nodes inherit from ASTNode and carry position: Position and scope: Scope | None attributes.

Base Classes

• ASTNode(position: Position, scope: Scope | None): Base class for all AST nodes

• Expression: Base class for all expression nodes

• Primary: Base class for atomic value types (extends Expression)

• ModuleInstantiation: Base class for module-related statements

• VectorElement: Base class for list comprehension elements

Literals

• Identifier(name: str): Variable, function, or module names

• StringLiteral(val: str): String values

• NumberLiteral(val: float): Numeric values

• BooleanLiteral(val: bool): true/false values

• UndefinedLiteral: The undef value (no additional fields)

• RangeLiteral(start: Expression, end: Expression, step: Expression): Range expressions [start:step:end]

Operators

All operators inherit from Expression and represent their respective operations with typed fields for operands. The AST preserves operator precedence and associativity as defined in OpenSCAD.

Arithmetic:

• AdditionOp(left: Expression, right: Expression): represents left + right

• SubtractionOp(left: Expression, right: Expression): represents left - right

• MultiplicationOp(left: Expression, right: Expression): represents left * right

• DivisionOp(left: Expression, right: Expression): represents left / right

• ModuloOp(left: Expression, right: Expression): represents left % right

• ExponentOp(left: Expression, right: Expression): represents left ^ right

• UnaryMinusOp(expr: Expression): represents -expr

Logical:

• LogicalAndOp(left: Expression, right: Expression): represents left && right

• LogicalOrOp(left: Expression, right: Expression): represents left || right

• LogicalNotOp(expr: Expression): represents !expr

Comparison:

• EqualityOp(left: Expression, right: Expression): represents left == right

• InequalityOp(left: Expression, right: Expression): represents left != right

• GreaterThanOp(left: Expression, right: Expression): represents left > right

• GreaterThanOrEqualOp(left: Expression, right: Expression): represents left >= right

• LessThanOp(left: Expression, right: Expression): represents left < right

• LessThanOrEqualOp(left: Expression, right: Expression): represents left <= right

Bitwise:

• BitwiseAndOp(left: Expression, right: Expression): represents left & right

• BitwiseOrOp(left: Expression, right: Expression): represents left | right

• BitwiseShiftLeftOp(left: Expression, right: Expression): represents left << right

• BitwiseShiftRightOp(left: Expression, right: Expression): represents left >> right

• BitwiseNotOp(expr: Expression): represents ~expr

Other:

• TernaryOp(condition: Expression, true_expr: Expression, false_expr: Expression): Represents condition ? true_expr : false_expr

Expressions

• LetOp(assignments: list[Assignment], body: Expression): let clause let(assignments) body

• EchoOp(arguments: list[Argument], body: Expression): echo clause echo(arguments) body

• AssertOp(arguments: list[Argument], body: Expression): assert clause assert(arguments) body

• FunctionLiteral(parameters: list[ParameterDeclaration], body: Expression): Anonymous function expression function(parameters) body

• PrimaryCall(left: Expression, arguments: list[Argument]): Function calls left(arguments)

• PrimaryIndex(left: Expression, index: Expression): Array indexing left[index]

• PrimaryMember(left: Expression, member: Identifier): Member access left.member

List Comprehensions

• ListComprehension(elements: list[VectorElement]): Vector/list literals [elements]

• ListCompFor(assignments: list[Assignment], body: VectorElement): for loops in list comprehensions for(assignments) body

• ListCompCFor(inits: list[Assignment], condition: Expression, incrs: list[Assignment], body: VectorElement): C-style for loops in list comprehensions for(inits; condition; incrs) body

• ListCompIf(condition: Expression, true_expr: VectorElement): Conditional inclusion without else if (condition) true_expr

• ListCompIfElse(condition: Expression, true_expr: VectorElement, false_expr: VectorElement): Conditional inclusion with else if (condition) true_expr else false_expr

• ListCompLet(assignments: list[Assignment], body: VectorElement): let expressions in list comprehensions let(assignments) body

• ListCompEach(body: VectorElement): each expressions (flattens nested lists) each body

Module Instantiations

• ModularCall(name: Identifier, arguments: list[Argument], children: list[ModuleInstantiation]): Module calls name(arguments) { children }

• ModularFor(assignments: list[Assignment], body: ModuleInstantiation): for loops in module bodies for(assignments) body

• ModularIntersectionFor(assignments: list[Assignment], body: ModuleInstantiation): intersection_for loops intersection_for(assignments) body

• ModularLet(assignments: list[Assignment], children: list[ModuleInstantiation]): let statements in module bodies let(assignments) { children }

• ModularEcho(arguments: list[Argument], children: list[ModuleInstantiation]): echo statements in module bodies echo(arguments) { children }

• ModularAssert(arguments: list[Argument], children: list[ModuleInstantiation]): assert statements in module bodies assert(arguments) { children }

• ModularIf(condition: Expression, true_branch: ModuleInstantiation): if statements in module bodies, with no else if(condition) true_branch

• ModularIfElse(condition: Expression, true_branch: ModuleInstantiation, false_branch: ModuleInstantiation): if/else statements in module bodies if(condition) true_branch else false_branch

• ModularModifierShowOnly(child: ModuleInstantiation): Show-Only modifier !child

• ModularModifierHighlight(child: ModuleInstantiation): Highlight modifier #child

• ModularModifierBackground(child: ModuleInstantiation): Background modifier %child

• ModularModifierDisable(child: ModuleInstantiation): Disabler modifier *child

Declarations

• ModuleDeclaration(name: Identifier, parameters: list[ParameterDeclaration], children: list[ModuleInstantiation | Assignment | FunctionDeclaration | ModuleDeclaration]): Module definitions module name(parameters) { children }

• FunctionDeclaration(name: Identifier, parameters: list[ParameterDeclaration], expr: Expression): Function definitions function name(parameters) = expr;

• ParameterDeclaration(name: Identifier, default: Expression | None): Function/module parameter with optional default value name=default or name

• Assignment(name: Identifier, expr: Expression): Variable assignments name = expr;

Statements

• UseStatement(filepath: StringLiteral): Represents use <filepath>

• IncludeStatement(filepath: StringLiteral): Represents include <filepath>

• PositionalArgument(expr: Expression): Function call positional arguments expr

• NamedArgument(name: Identifier, expr: Expression): Function call named arguments name=expr

Comments

• CommentLine(text: str): Single-line comments // str

• CommentSpan(text: str): Multi-line comments /* str */

All AST node classes are fully documented with docstrings that include: - Description of what the node represents - OpenSCAD code examples - Field/attribute descriptions - Usage notes

API Reference

Main Functions

getOpenSCADParser(reduce_tree=False, debug=False)

Create an Arpeggio parser instance for OpenSCAD code.

param reduce_tree:

If True, reduces single-child nodes in parse tree

param debug:

If True, enables debug output

returns:

ParserPython instance

getASTfromString(code: str, include_comments: bool = False, origin: str = "<string>")

Parse OpenSCAD code from a string and return its AST.

param code:

The OpenSCAD source code to be parsed

param include_comments:

If True, include comment nodes in the AST (default: False)

param origin:

Origin identifier used in source position tracking (default: “<string>”)

returns:

AST node or list of AST nodes (for top-level statements)

rtype:

ASTNode | list[ASTNode] | None

getASTfromFile(file: str, include_comments: bool = False, process_includes: bool = True)

Parse an OpenSCAD source file and return its AST. Includes automatic caching that invalidates when the file’s modification timestamp changes.

param file:

The OpenSCAD source file to be parsed

param include_comments:

If True, include comments in the AST (default: False)

param process_includes:

If True, process include statements and replace with file contents (default: True). When False, the AST will contain IncludeStatement nodes where includes appear.

returns:

List of AST nodes (for top-level statements)

rtype:

list[ASTNode] | None

raises FileNotFoundError:

If the specified file does not exist

raises Exception:

If there is an error while reading the file

Note: When process_includes=True (default), the AST will NOT contain IncludeStatement nodes because includes are processed before parsing. When process_includes=False, IncludeStatement nodes will appear in the AST where include <file> statements exist in the source code.

Unlike include statements, use <file> statements are ALWAYS parsed into UseStatement AST nodes regardless of the process_includes setting, since use only affects runtime lookup, not source inclusion.

getASTfromLibraryFile(currfile: str, libfile: str, include_comments: bool = False, process_includes: bool = True)

Find and parse an OpenSCAD library file using OpenSCAD’s search path rules. Searches in: current file directory, OPENSCADPATH, and platform default paths.

param currfile:

Full path to the current OpenSCAD file (can be empty string)

param libfile:

Partial or full path to the library file to find

param include_comments:

If True, include comments in the AST (default: False)

param process_includes:

If True, process include statements (default: True). When False, the AST will contain IncludeStatement nodes where includes appear.

returns:

Tuple of (AST nodes list, absolute file path). The AST list is None if empty or not valid.

rtype:

tuple[list[ASTNode] | None, str]

raises FileNotFoundError:

If the library file cannot be found

raises Exception:

If there is an error while reading or parsing the file

Note: The process_includes parameter affects the AST structure (see getASTfromFile documentation).

parse_ast(parser, code, file="", source_map=None)

Parse OpenSCAD code and generate an AST (lower-level API).

param parser:

Arpeggio parser instance from getOpenSCADParser()

param code:

OpenSCAD code string to parse

param file:

Optional file path for source location tracking

param source_map:

Optional SourceMap for multi-origin position tracking

returns:

AST node or list of AST nodes (for top-level statements)

clear_ast_cache()

Clear the in-memory AST cache, forcing all subsequent calls to getASTfromFile() to re-parse files.

This function removes all cached AST trees from memory.

build_scopes(ast: list[ASTNode]) -> Scope

Build a scope tree over an AST and attach a scope attribute to every node.

param ast:

A list of top-level AST nodes (as returned by the getAST* functions)

returns:

The root Scope object

Scope

Represents a lexical scope with three independent namespaces (variables, functions, modules), mirroring OpenSCAD’s scoping rules.

• scope.lookup_variable(name) — search this scope and its parents

• scope.lookup_function(name) — search this scope and its parents

• scope.lookup_module(name) — search this scope and its parents

• scope.parent — the enclosing scope (None for root)

to_openscad(nodes: list[ASTNode], indent_width: int = 4)

Convert a list of AST nodes to formatted OpenSCAD source code.

param nodes:

Top-level AST nodes as returned by the getAST* functions.

param indent_width:

Spaces per indentation level (default: 4).

returns:

Formatted OpenSCAD source as a string.

Serialization Functions

ast_to_dict(ast: ASTNode | Sequence[ASTNode] | None, include_position: bool = True)

Convert an AST to a Python dictionary (JSON-serializable).

param ast:

An AST node, sequence of AST nodes, or None

param include_position:

If True, include source position information (default: True)

returns:

A dictionary representation of the AST, a list of dictionaries, or None

rtype:

dict[str, Any] | list[dict[str, Any]] | None

ast_to_json(ast: ASTNode | Sequence[ASTNode] | None, include_position: bool = True, indent: int | None = 2)

Serialize an AST to a JSON string.

param ast:

An AST node, sequence of AST nodes, or None

param include_position:

If True, include source position information (default: True)

param indent:

Indentation level for pretty-printing. Use None for compact output (default: 2)

returns:

A JSON string representation of the AST

rtype:

str

ast_from_dict(data: dict[str, Any] | list[dict[str, Any]] | None)

Reconstruct an AST from a Python dictionary.

param data:

A dictionary, list of dictionaries, or None (as returned by ast_to_dict)

returns:

An AST node, list of AST nodes, or None

rtype:

ASTNode | list[ASTNode] | None

raises ValueError:

If the data contains an unknown node type or is malformed

ast_from_json(json_str: str)

Deserialize an AST from a JSON string.

param json_str:

A JSON string (as returned by ast_to_json)

returns:

An AST node, list of AST nodes, or None

rtype:

ASTNode | list[ASTNode] | None

raises ValueError:

If the JSON contains an unknown node type or is malformed

raises json.JSONDecodeError:

If the string is not valid JSON

ast_to_yaml(ast: ASTNode | Sequence[ASTNode] | None, include_position: bool = True)

Serialize an AST to a YAML string.

Requires PyYAML to be installed: pip install openscad_parser[yaml]

param ast:

An AST node, sequence of AST nodes, or None

param include_position:

If True, include source position information (default: True)

returns:

A YAML string representation of the AST

rtype:

str

raises ImportError:

If PyYAML is not installed

ast_from_yaml(yaml_str: str)

Deserialize an AST from a YAML string.

Requires PyYAML to be installed: pip install openscad_parser[yaml]

param yaml_str:

A YAML string (as returned by ast_to_yaml)

returns:

An AST node, list of AST nodes, or None

rtype:

ASTNode | list[ASTNode] | None

raises ImportError:

If PyYAML is not installed

raises ValueError:

If the YAML contains an unknown node type or is malformed

AST Node Classes

All AST node classes are located in openscad_parser.ast. Each node class:

• Inherits from ASTNode (or a subclass like Expression)

• Has a position attribute of type Position for source location

• Implements __str__() for string representation

• Is a dataclass with typed fields

Import commonly used classes:

from openscad_parser.ast import (
    # Base classes
    ASTNode, Expression, Primary,

    # Literals
    Identifier, StringLiteral, NumberLiteral, BooleanLiteral,

    # Operators
    AdditionOp, SubtractionOp, MultiplicationOp, DivisionOp,
    LogicalAndOp, LogicalOrOp, EqualityOp, InequalityOp,

    # Expressions
    PrimaryCall, PrimaryIndex, PrimaryMember,
    LetOp, EchoOp, AssertOp, TernaryOp,

    # Modules
    ModuleDeclaration, ModularCall, ModularFor,

    # Functions
    FunctionDeclaration,

    # Statements
    Assignment, UseStatement, IncludeStatement,
    PositionalArgument, NamedArgument, ParameterDeclaration
)

Source Position Tracking

All AST nodes include source position information:

from openscad_parser.ast import getASTfromFile, Position

ast = getASTfromFile("example.scad")
assignment = ast[0]

position = assignment.position
print(position.origin)        # "example.scad" (origin identifier)
print(position.line)          # 1 (1-indexed line number)
print(position.column)        # 1 (1-indexed column number)
print(position.start_offset)  # 0 (0-based byte offset of token start within origin)
print(position.end_offset)    # N (0-based exclusive byte offset of token end)

The Position dataclass carries both line/column coordinates and byte offsets relative to the origin’s content. For single-file parses these equal file byte offsets; for multi-origin parses (e.g. after include expansion) they are relative to each included file.

Serialization

AST trees can be serialized to JSON or YAML formats and deserialized back to AST nodes. This is useful for caching, storage, or transferring AST data between processes.

JSON Serialization

Serialize an AST to JSON:

from openscad_parser.ast import getASTfromString, ast_to_json, ast_from_json

# Parse code to AST
ast = getASTfromString("cube(10);")

# Serialize to JSON string
json_str = ast_to_json(ast, include_position=True, indent=2)

# Deserialize back to AST
ast_restored = ast_from_json(json_str)

The ast_to_json() function accepts: - ast: An AST node, sequence of AST nodes, or None - include_position: If True, include source position information (default: True) - indent: Indentation level for pretty-printing. Use None for compact output (default: 2)

Dictionary Serialization

You can also work with Python dictionaries directly:

from openscad_parser.ast import getASTfromString, ast_to_dict, ast_from_dict

ast = getASTfromString("x = 42;")

# Convert to dictionary
data = ast_to_dict(ast, include_position=True)

# Convert back to AST
ast_restored = ast_from_dict(data)

YAML Serialization

For YAML serialization, you need to install PyYAML:

pip install openscad_parser[yaml]

Then serialize to YAML:

from openscad_parser.ast import getASTfromString, ast_to_yaml, ast_from_yaml

ast = getASTfromString("cube(10);")

# Serialize to YAML string
yaml_str = ast_to_yaml(ast, include_position=True)

# Deserialize back to AST
ast_restored = ast_from_yaml(yaml_str)

The ast_to_yaml() function accepts: - ast: An AST node, sequence of AST nodes, or None - include_position: If True, include source position information (default: True)

Serialization Functions

All serialization functions can be imported directly from openscad_parser.ast (recommended):

from openscad_parser.ast import (
    ast_to_dict,
    ast_to_json,
    ast_to_yaml,
    ast_from_dict,
    ast_from_json,
    ast_from_yaml,
)

They are also available from openscad_parser.ast.serialization:

from openscad_parser.ast.serialization import (
    ast_to_dict,
    ast_to_json,
    ast_to_yaml,
    ast_from_dict,
    ast_from_json,
    ast_from_yaml,
)

Pretty-Printing

The to_openscad() function converts an AST back to formatted OpenSCAD source code:

from openscad_parser.ast import getASTfromString, to_openscad

code = "module box(w,h){cube([w,h,1]);}"
ast = getASTfromString(code)

formatted = to_openscad(ast)
# module box(w, h) {
#     cube([w, h, 1]);
# }
print(formatted)

The pretty-printer normalises whitespace and indentation while preserving the logical structure of the code. It supports all AST node types including modules, functions, control structures, modifiers, list comprehensions, and comments.

to_openscad(nodes, indent_width=4)

Convert a list of AST nodes to formatted OpenSCAD source.

param nodes:

Top-level AST nodes (as returned by getAST* functions).

param indent_width:

Spaces per indentation level (default: 4).

returns:

Formatted OpenSCAD source code as a string.

• Blank lines are inserted before and after module/function declarations.

• Single-child module instantiations are formatted inline; multiple children use a block.

• Operator precedence is preserved — parentheses are re-inserted exactly where needed.

• Boolean literals are always written as true / false.

• Ternary expressions are formatted across three lines (condition, ? true, : false); block-formatted branches (let, assert, echo, list comprehensions, long calls) align their closing delimiter with their visual keyword column.

• let(), assert(), and echo() expressions place their body on the next line.

• List comprehensions containing for loops always expand to block form; if (condition) elements include parentheses around the condition.

• Long argument/parameter lists (> 100 characters) are formatted one argument per line, with each argument expression individually reformatted (ternaries, let, list comprehensions, nested long calls).

• Comments are preserved when the AST was parsed with include_comments=True.

Controlling indentation:

from openscad_parser.ast import getASTfromString, to_openscad

ast = getASTfromString("module m() { cube(1); }")
print(to_openscad(ast, indent_width=2))
# module m() {
#   cube(1.0);
# }

Command-Line Interface

The openscad-parser CLI is installed alongside the package:

pip install openscad-parser

Usage:

openscad-parser [OPTIONS] [FILE]

Read from a file or - for stdin. Default output is JSON.

Options:

--json

Output AST as JSON (default).

--yaml

Output AST as YAML (requires pip install openscad_parser[yaml]).

--format

Output reformatted OpenSCAD source code.

--indent N

Indentation width in spaces (default: 4). Applies to --format and --json.

--include-comments

Include comment nodes in the output.

--no-includes

Do not expand include <...> statements; keep IncludeStatement nodes instead.

Examples:

Dump AST as JSON:

openscad-parser model.scad
openscad-parser - < model.scad         # stdin

Reformat OpenSCAD source:

openscad-parser --format model.scad
openscad-parser --format --indent 2 model.scad

Output YAML:

openscad-parser --yaml model.scad

Include comments in the AST:

openscad-parser --include-comments --json model.scad

Error Handling

The parser will raise SyntaxError exceptions for invalid OpenSCAD syntax:

from openscad_parser.ast import getASTfromString

try:
    code = "x = ;"  # Invalid syntax
    ast = getASTfromString(code)
except SyntaxError as e:
    print(f"Parse error: {e}")

File operations will raise FileNotFoundError for missing files:

from openscad_parser.ast import getASTfromFile, getASTfromLibraryFile

try:
    ast = getASTfromFile("nonexistent.scad")
except FileNotFoundError as e:
    print(f"File not found: {e}")

try:
    ast, path = getASTfromLibraryFile("main.scad", "missing_lib.scad")
except FileNotFoundError as e:
    print(f"Library file not found: {e}")

Advanced Usage

File Caching

The getASTfromFile() function automatically caches parsed ASTs in memory:

from openscad_parser.ast import getASTfromFile

# First call parses and caches
ast1 = getASTfromFile("model.scad")

# Second call returns cached AST (same object)
ast2 = getASTfromFile("model.scad")
assert ast1 is ast2  # True - same cached object

# After file modification, cache is invalidated and file is re-parsed
# (modify model.scad here)
ast3 = getASTfromFile("model.scad")
assert ast1 is not ast3  # True - new parse after modification

Cache entries are automatically invalidated when a file’s modification timestamp changes. To manually clear the cache:

from openscad_parser.ast import clear_ast_cache

clear_ast_cache()  # Clear all cached ASTs

Reusing Parser Instances

Parser instances can be reused for parsing multiple code snippets:

parser = getOpenSCADParser(reduce_tree=False)

# Parse multiple files
ast1 = parse_ast(parser, code1, file="file1.scad")
ast2 = parse_ast(parser, code2, file="file2.scad")

Note: For some use cases (like testing), you may need to create fresh parser instances to avoid memoization issues.

Traversing the AST

The AST is a tree structure that can be traversed recursively:

def visit_node(node):
    """Recursively visit AST nodes."""
    if isinstance(node, Assignment):
        print(f"Assignment: {node.name.name}")
        visit_node(node.expr)
    elif isinstance(node, AdditionOp):
        print("Addition operation")
        visit_node(node.left)
        visit_node(node.right)
    elif isinstance(node, NumberLiteral):
        print(f"Number: {node.val}")
    # ... handle other node types

from openscad_parser.ast import getASTfromString

code = "x = 10; y = 20;"
ast = getASTfromString(code)
for node in ast:
    visit_node(node)

Scope Tracking

The parser can build a scope tree over the AST, resolving variable, function, and module names according to OpenSCAD’s three-namespace scoping rules:

from openscad_parser.ast import getASTfromString, build_scopes

ast = getASTfromString("""
    x = 10;
    module box(size = x) { cube(size); }
    box();
""")

root_scope = build_scopes(ast)

# Look up names in the root scope
print(root_scope.lookup_variable("x"))   # Assignment node
print(root_scope.lookup_module("box"))   # ModuleDeclaration node

# Each AST node has a .scope attribute pointing to its enclosing scope
box_decl = ast[1]
cube_call = box_decl.children[0]
print(cube_call.scope.lookup_variable("size"))  # ParameterDeclaration node

build_scopes(ast) returns the root Scope object and attaches a scope attribute to every node in the tree. Scopes form a parent chain so lookups fall through to enclosing scopes automatically. Declarations (variables, functions, modules) inside a block are hoisted to the top of that block’s scope before child nodes are visited.

Testing

The project includes a comprehensive test suite. Run tests with:

uv run pytest tests/

Development

Contributions are welcome! The project uses:

• Arpeggio for PEG parsing

• pytest for testing

License

MIT License - see LICENSE file for details.

Links

• GitHub Repository

• Issue Tracker

• Releases