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feat(validator): detect IF/Switch/Filter conditional branch fan-out misuse

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Add CONDITIONAL_BRANCH_FANOUT warning when conditional nodes have all
connections on main[0] with higher outputs empty, indicating both
branches execute together instead of being split by condition.

Extract getShortNodeType() and getConditionalOutputInfo() helpers to
deduplicate conditional node detection logic.

Conceived by Romuald Czlonkowski - https://www.aiadvisors.pl/en

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
czlonkowski
2026-03-08 08:10:04 +01:00
parent 2e472ebc6c
commit 2081645cfa
10 changed files with 688 additions and 29 deletions
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109
dist/services/workflow-validator.js vendored
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@@ -422,6 +422,9 @@ class WorkflowValidator {
if (outputKey === 'ai_tool') {
this.validateAIToolSource(sourceNode, result);
}
if (outputKey === 'main') {
this.validateNotAISubNode(sourceNode, result);
}
this.validateConnectionOutputs(sourceName, outputConnections, nodeMap, nodeIdMap, result, outputKey);
}
}
@@ -443,6 +446,7 @@ class WorkflowValidator {
if (outputType === 'main' && sourceNode) {
this.validateErrorOutputConfiguration(sourceName, sourceNode, outputs, nodeMap, result);
this.validateOutputIndexBounds(sourceNode, outputs, result);
this.validateConditionalBranchUsage(sourceNode, outputs, result);
}
outputs.forEach((outputConnections, outputIndex) => {
if (!outputConnections)
@@ -644,6 +648,57 @@ class WorkflowValidator {
code: 'INVALID_AI_TOOL_SOURCE'
});
}
getNodeOutputTypes(nodeType) {
const normalizedType = node_type_normalizer_1.NodeTypeNormalizer.normalizeToFullForm(nodeType);
const nodeInfo = this.nodeRepository.getNode(normalizedType);
if (!nodeInfo || !nodeInfo.outputs)
return null;
const outputs = nodeInfo.outputs;
if (!Array.isArray(outputs))
return null;
for (const output of outputs) {
if (typeof output === 'string' && output.startsWith('={{')) {
return null;
}
}
return outputs;
}
validateNotAISubNode(sourceNode, result) {
const outputTypes = this.getNodeOutputTypes(sourceNode.type);
if (!outputTypes)
return;
const hasMainOutput = outputTypes.some(t => t === 'main');
if (hasMainOutput)
return;
const aiTypes = outputTypes.filter(t => t !== 'main');
const expectedType = aiTypes[0] || 'ai_languageModel';
result.errors.push({
type: 'error',
nodeId: sourceNode.id,
nodeName: sourceNode.name,
message: `Node "${sourceNode.name}" (${sourceNode.type}) is an AI sub-node that outputs "${expectedType}" connections. ` +
`It cannot be used with "main" connections. Connect it to an AI Agent or Chain via "${expectedType}" instead.`,
code: 'AI_SUBNODE_MAIN_CONNECTION'
});
}
getShortNodeType(sourceNode) {
const normalizedType = node_type_normalizer_1.NodeTypeNormalizer.normalizeToFullForm(sourceNode.type);
return normalizedType.replace(/^(n8n-)?nodes-base\./, '');
}
getConditionalOutputInfo(sourceNode) {
const shortType = this.getShortNodeType(sourceNode);
if (shortType === 'if' || shortType === 'filter') {
return { shortType, expectedOutputs: 2 };
}
if (shortType === 'switch') {
const rules = sourceNode.parameters?.rules?.values || sourceNode.parameters?.rules;
if (Array.isArray(rules)) {
return { shortType, expectedOutputs: rules.length + 1 };
}
return null;
}
return null;
}
validateOutputIndexBounds(sourceNode, outputs, result) {
const normalizedType = node_type_normalizer_1.NodeTypeNormalizer.normalizeToFullForm(sourceNode.type);
const nodeInfo = this.nodeRepository.getNode(normalizedType);
@@ -658,18 +713,12 @@ class WorkflowValidator {
}
if (mainOutputCount === 0)
return;
const shortType = normalizedType.replace(/^(n8n-)?nodes-base\./, '');
if (shortType === 'switch') {
const rules = sourceNode.parameters?.rules?.values || sourceNode.parameters?.rules;
if (Array.isArray(rules)) {
mainOutputCount = rules.length + 1;
}
else {
return;
}
const conditionalInfo = this.getConditionalOutputInfo(sourceNode);
if (conditionalInfo) {
mainOutputCount = conditionalInfo.expectedOutputs;
}
if (shortType === 'if' || shortType === 'filter') {
mainOutputCount = 2;
else if (this.getShortNodeType(sourceNode) === 'switch') {
return;
}
if (sourceNode.onError === 'continueErrorOutput') {
mainOutputCount += 1;
@@ -691,6 +740,44 @@ class WorkflowValidator {
}
}
}
validateConditionalBranchUsage(sourceNode, outputs, result) {
const conditionalInfo = this.getConditionalOutputInfo(sourceNode);
if (!conditionalInfo || conditionalInfo.expectedOutputs < 2)
return;
const { shortType, expectedOutputs } = conditionalInfo;
const main0Count = outputs[0]?.length || 0;
if (main0Count < 2)
return;
const hasHigherIndexConnections = outputs.slice(1).some(conns => conns && conns.length > 0);
if (hasHigherIndexConnections)
return;
let message;
if (shortType === 'if' || shortType === 'filter') {
const isFilter = shortType === 'filter';
const displayName = isFilter ? 'Filter' : 'IF';
const trueLabel = isFilter ? 'matched' : 'true';
const falseLabel = isFilter ? 'unmatched' : 'false';
message = `${displayName} node "${sourceNode.name}" has ${main0Count} connections on the "${trueLabel}" branch (main[0]) ` +
`but no connections on the "${falseLabel}" branch (main[1]). ` +
`All ${main0Count} target nodes execute together on the "${trueLabel}" branch, ` +
`while the "${falseLabel}" branch has no effect. ` +
`Split connections: main[0] for ${trueLabel}, main[1] for ${falseLabel}.`;
}
else {
message = `Switch node "${sourceNode.name}" has ${main0Count} connections on output 0 ` +
`but no connections on any other outputs (1-${expectedOutputs - 1}). ` +
`All ${main0Count} target nodes execute together on output 0, ` +
`while other switch branches have no effect. ` +
`Distribute connections across outputs to match switch rules.`;
}
result.warnings.push({
type: 'warning',
nodeId: sourceNode.id,
nodeName: sourceNode.name,
message,
code: 'CONDITIONAL_BRANCH_FANOUT'
});
}
validateInputIndexBounds(sourceName, targetNode, connection, result) {
const normalizedType = node_type_normalizer_1.NodeTypeNormalizer.normalizeToFullForm(targetNode.type);
const nodeInfo = this.nodeRepository.getNode(normalizedType);