Sverchok Agents Code Validator

Sverchok Code Validator Agent

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:

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:

if not any(s.is_linked for s in self.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:

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:

class SvMyNode(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:

1. Early exit if no output connected
2. Read inputs with sv_get(default=...)
3. Match input lengths with match_long_repeat()
4. Process each object in a loop
5. 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:

# WRONG
self.outputs['Names'].sv_set(["Wall_001"])
# CORRECT
self.outputs['Names'].sv_set([["Wall_001"]])

CHECK 11: BMesh Cleanup (bm.free())

Severity: BLOCKER

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:

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.

Correct pattern:

verts = self.inputs['Vertices'].sv_get(default=[[]])
scale = self.inputs['Scale'].sv_get(default=[[1.0]])

CHECK 17: Registration Completeness

Severity: BLOCKER

Custom node classes MUST define all required registration attributes.

Required attributes:

Recommended attributes:

Flag BLOCKER if: bl_idname or bl_label is missing. Flag INFO if sv_category or bl_icon is missing.

CHECK 18: Property Type Validation

Severity: BLOCKER

Verify that bpy.props types are used correctly in node class annotations.

Flag BLOCKER if:

• FloatProperty used where IntProperty is needed (counts, indices)
• CollectionProperty or PointerProperty used without proper registration
• Property type annotation uses = instead of : (Blender 2.80+ requires annotation syntax)

Correct:

count: IntProperty(name='Count', default=5, update=updateNode)

Wrong:

count = IntProperty(name='Count', default=5, update=updateNode)  # Old syntax

CHECK 19: Edge/Face Data Format Validation

Severity: BLOCKER

Edge data MUST be tuples/lists of exactly 2 integers. Face data MUST be tuples/lists of 3 or more integers.

Detection: Trace edge and face data construction. Verify tuple sizes.

Flag BLOCKER if:

• Edge tuples contain fewer or more than 2 elements
• Face tuples contain fewer than 3 elements
• Edge/face indices are floats instead of integers

Severity Summary Decision Tree

Code will crash or corrupt data?
├── YES → BLOCKER
│   ├── Wrong nesting level on sv_set() (CHECK 1)
│   ├── Missing updateNode on property (CHECK 2)
│   ├── zip() without match_long_repeat (CHECK 4)
│   ├── Socket creation in process() (CHECK 5)
│   ├── Invalid SNLite alias (CHECK 7)
│   ├── Wrong IfcSverchok nesting (CHECK 10)
│   ├── Missing bm.free() (CHECK 11)
│   ├── Missing/wrong imports (CHECK 13)
│   ├── Socket name mismatch sv_init↔process (CHECK 14)
│   ├── Missing bl_idname or bl_label (CHECK 17)
│   ├── Wrong property annotation syntax (CHECK 18)
│   └── Invalid edge/face tuple size (CHECK 19)
├── NO → Code has bug or missing best practice?
│   ├── YES → WARNING
│   │   ├── No output connection check (CHECK 3)
│   │   ├── Input mutation without deepcopy (CHECK 6)
│   │   ├── Non-standard process() pattern (CHECK 9)
│   │   ├── Wrong match_long_repeat unpacking (CHECK 15)
│   │   └── sv_get() without default (CHECK 16)
│   └── NO → Convention issue?
│       ├── YES → INFO
│       │   ├── Missing Triggers/Tooltip docstring (CHECK 8)
│       │   ├── NumPy optimization opportunity (CHECK 12)
│       │   └── Missing sv_category or bl_icon (CHECK 17)
│       └── NO → PASS

Auto-Fix Patterns

When a check fails, apply these fixes automatically where safe:

Validation Report Format

After running all checks, produce a report:

## Validation Report
Target: Sverchok v1.4.0
Total Issues: N

### BLOCKERS (N)
- [CHECK X] Description — file:line

### WARNINGS (N)
- [CHECK X] Description — file:line

### INFO (N)
- [CHECK X] Description — file:line

### Auto-Fixes Applied (N)
- Description — file:line

Reference Links

• Validation Rules: references/methods.md
• Before/After Examples: references/examples.md
• Anti-Patterns Catalog: references/anti-patterns.md

Dependency Skills

• sverchok-errors-common — Common Sverchok error patterns and diagnosis
• sverchok-impl-custom-nodes — Custom node development patterns
• sverchok-impl-ifcsverchok — IfcSverchok integration patterns

Official Documentation

• Sverchok GitHub: https://github.com/nortikin/sverchok
• Sverchok Documentation: https://nortikin.github.io/sverchok/
• Sverchok Custom Nodes: https://github.com/nortikin/sverchok/wiki/Custom-Nodes