Systematic validation checklist for reviewing Sverchok node code. Run this checklist against any Sverchok Python code to identify errors, anti-patterns, and correctness issues. Targets Sverchok v1.4.0 on Blender 4.0+.
Quick Reference: When to Activate
Activate this validator when:
Reviewing, auditing, or validating Sverchok node scripts
Checking custom node code before deployment
Generating new Sverchok node code (run validator on output)
Investigating data corruption, silent failures, or incorrect geometry
Reviewing SNLite scripts, SN Functor B scripts, or custom node classes
Validation Checklist
Run each check in order. Each check has a severity level:
BLOCKER: Code will crash, produce data corruption, or cause silent failures
WARNING: Code has a bug, performance issue, or missing best practice
INFO: Code works but does not follow Sverchok conventions
CHECK 1: Data Nesting Correctness
Severity: BLOCKER
Verify that all sv_set() calls use the correct nesting level for their socket type.
Required nesting levels:
Socket Type
Required Level
Example
SvVerticesSocket
3
[[(x,y,z), (x,y,z)]]
SvStringsSocket
2
[[1, 2, 3]]
Edges
2
[[(0,1), (1,2)]]
Faces
2
[[(0,1,2)]]
SvMatrixSocket
1
[Matrix(), Matrix()]
Detection: Find all self.outputs[...].sv_set(...) calls. Trace the argument back to its construction. Verify the outermost list depth matches the socket type.
Flag BLOCKER if:
Vertices are output at level 2 (missing object wrapper): sv_set([(0,0,0), (1,0,0)])
Strings/edges/faces are output at level 1 (flat list): sv_set([1, 2, 3])
Matrices are output at level 2 (double-wrapped): sv_set([[Matrix()]])
CHECK 2: updateNode Callback on All Properties
Severity: BLOCKER
Every bpy.props.*Property declaration that affects node output MUST include update=updateNode.
Detection: Find all lines matching *Property( (FloatProperty, IntProperty, BoolProperty, EnumProperty, StringProperty, FloatVectorProperty, IntVectorProperty, BoolVectorProperty). Verify each contains update=updateNode.
Flag BLOCKER if: Any property lacks update=updateNode.
Exception: Properties that only control UI display (not computation) may omit updateNode. Flag INFO instead if the property name suggests UI-only use (e.g., show_options, expand_ui).
CHECK 3: Output Connection Check
Severity: WARNING
The process() method SHOULD exit early if no outputs are connected.
Detection: Check the first lines of process() for:
ifnotany(s.is_linked for s inself.outputs):
return
Flag WARNING if: process() does not check output connections before performing computation. This causes unnecessary computation when no downstream node uses the output.
CHECK 4: match_long_repeat Before zip
Severity: BLOCKER
When iterating over multiple inputs with zip(), inputs MUST first be matched using match_long_repeat().
Detection: Find all zip(...) calls in process() where arguments are socket input data. Check that match_long_repeat() was called on those inputs before the zip().
Flag BLOCKER if: zip() is used on socket inputs without prior match_long_repeat(). Plain zip() silently truncates data to the shortest input.
CHECK 5: Socket Creation Only in sv_init/sv_update
Severity: BLOCKER
Socket creation (self.inputs.new(...) or self.outputs.new(...)) MUST only occur in sv_init() or sv_update().
Detection: Find all .inputs.new( and .outputs.new( calls. Verify each occurs inside sv_init or sv_update methods.
Flag BLOCKER if: Socket creation occurs inside process(). This creates a new socket on every evaluation, corrupting the node.
CHECK 6: deepcopy for Input Data
Severity: WARNING
Input data retrieved via sv_get() SHOULD NOT be mutated in-place without deepcopy=True.
Detection: Find sv_get() calls. If the returned data is subsequently modified (.append(), [i] = ..., del, .pop(), .extend(), .insert(), .sort(), .reverse()), verify that deepcopy=True was passed (or that a manual copy was made).
Flag WARNING if: Input data is mutated without deepcopy. This corrupts cached data and affects upstream nodes.
Note: sv_get(deepcopy=True) is the default in recent Sverchok versions. Flag only if deepcopy=False is explicitly set and data is mutated.
CHECK 7: Correct SNLite Aliases
Severity: BLOCKER
In SNLite header declarations, socket type aliases MUST use the correct single-letter codes.
Valid aliases:
Alias
Socket Type
s
SvStringsSocket
v
SvVerticesSocket
m
SvMatrixSocket
o
SvObjectSocket
C
SvCurveSocket
S
SvSurfaceSocket
So
SvSolidSocket
SF
SvScalarFieldSocket
VF
SvVectorFieldSocket
D
SvDictionarySocket
FP
SvFilePathSocket
Flag BLOCKER if: SNLite header uses invalid aliases such as vertices, string, matrix, float, int, vector.
CHECK 8: Node Docstring Format
Severity: INFO
Custom node classes SHOULD include a docstring with Triggers: and Tooltip: lines.
Expected format:
classSvMyNode(SverchCustomTreeNode, bpy.types.Node):
"""
Triggers: keyword1 keyword2
Tooltip: Short description
"""
Flag INFO if: Docstring is missing, or Triggers: / Tooltip: lines are absent. These are used by Sverchok's node search (Shift+S).
CHECK 9: Standard Process Method Pattern
Severity: WARNING
The process() method SHOULD follow the standard 5-step pattern:
Early exit if no output connected
Read inputs with sv_get(default=...)
Match input lengths with match_long_repeat()
Process each object in a loop
Set outputs with sv_set()
Flag WARNING if: process() deviates significantly (e.g., missing default values on sv_get, no list iteration, direct scalar output without wrapping).
CHECK 10: IfcSverchok Double-Nesting
Severity: BLOCKER
Data sent to IfcSverchok nodes MUST use standard Sverchok nesting (level 2 for strings).
Detection: If the node tree contains IfcSverchok nodes (bl_idname starting with SvIfc), verify that all data passed to IFC node inputs follows Sverchok nesting conventions.
Flag BLOCKER if: Single-nested data is passed to IFC nodes:
Every bmesh.new() or bmesh_from_pydata() call MUST have a corresponding bm.free() call.
Detection: Track BMesh variable assignments. Verify each has a bm.free() call after the last usage. Exception: BMesh obtained via bmesh.from_edit_mesh() must NOT be freed manually.
Flag BLOCKER if: A standalone BMesh is created without bm.free(). This leaks memory.
CHECK 12: NumPy Optimization Opportunities
Severity: INFO
Flag opportunities where Python loops over vertex/numeric data could be replaced with NumPy vectorized operations.
Detection: Find for loops that iterate over vertex lists performing element-wise arithmetic.
Flag INFO if: A loop performs operations like (v[0] * s, v[1] * s, v[2] * s) that could be (np.array(verts) * s).tolist().
CHECK 13: Import Validation
Severity: BLOCKER
Verify that all Sverchok imports are correct and available.
Required imports per pattern:
Usage
Required Import
updateNode
from sverchok.data_structure import updateNode
match_long_repeat
from sverchok.data_structure import match_long_repeat
SverchCustomTreeNode
from sverchok.node_tree import SverchCustomTreeNode
bmesh_from_pydata
from sverchok.utils.sv_bmesh_utils import bmesh_from_pydata
pydata_from_bmesh
from sverchok.utils.sv_bmesh_utils import pydata_from_bmesh
SvNoDataError
from sverchok.core.sv_custom_exceptions import SvNoDataError
Flag BLOCKER if: Code uses updateNode, match_long_repeat, or SverchCustomTreeNode without the correct import statement. Flag BLOCKER if code imports from non-existent Sverchok modules.
CHECK 14: Socket Name Consistency sv_init↔process
Severity: BLOCKER
Socket names used in sv_get() / sv_set() calls in process() MUST match the names defined in sv_init().
Detection: Extract socket names from self.inputs.new('...', 'Name') and self.outputs.new('...', 'Name') in sv_init(). Compare against self.inputs['Name'] and self.outputs['Name'] references in process().
Flag BLOCKER if: A socket name in process() does not match any socket created in sv_init(). This causes a KeyError at runtime.
CHECK 15: match_long_repeat Unpacking Pattern
Severity: WARNING
The result of match_long_repeat() MUST be unpacked correctly.
Correct pattern:
verts, scale = match_long_repeat([verts, scale])
Flag WARNING if: Result is not unpacked (assigned to single variable) or unpacking count does not match input count.
CHECK 16: sv_get Default Pattern
Severity: WARNING
sv_get() calls SHOULD provide a default parameter for optional inputs.
Detection: Find sv_get() calls without default= on non-mandatory inputs.
Flag WARNING if: An optional input uses sv_get() without a default value. This raises an exception when the socket is unconnected.
