Added code to detect execution flows with long straight-line code flow graph segments. This is not captured in the cyclical code complexity calculations that we normally use to determine if code is too complex to analyze.

packages/pyright-internal/src/analyzer/binder.ts

@@ -93,6 +93,7 @@ import {
     FlowLabel,
     FlowNarrowForPattern,
     FlowNode,
+    FlowNodeCounter,
     FlowPostContextManagerLabel,
     FlowPostFinally,
     FlowPreFinallyGate,
@@ -142,6 +143,12 @@ interface ClassVarInfo {
     classVarTypeNode: ExpressionNode | undefined;
 }
 
+// For each flow node within an execution context, we'll add a small
+// amount to the complexity factor. Without this, the complexity
+// calculation fails to take into account large numbers of non-cyclical
+// flow nodes. This number is somewhat arbitrary and is tuned empirically.
+const flowNodeComplexityFactor = 0.05;
+
 export class Binder extends ParseTreeWalker {
     private readonly _fileInfo: AnalyzerFileInfo;
 
@@ -248,6 +255,8 @@ export class Binder extends ParseTreeWalker {
             isBuiltInModule ? ScopeType.Builtin : ScopeType.Module,
             this._fileInfo.builtinsScope,
             () => {
+                const flowNodeCounter = new FlowNodeCounter();
+
                 AnalyzerNodeInfo.setScope(node, this._currentScope);
                 AnalyzerNodeInfo.setFlowNode(node, this._currentFlowNode!);
 
@@ -275,7 +284,10 @@ export class Binder extends ParseTreeWalker {
                 AnalyzerNodeInfo.setAfterFlowNode(node, this._currentFlowNode);
 
                 AnalyzerNodeInfo.setCodeFlowExpressions(node, this._currentScopeCodeFlowExpressions!);
-                AnalyzerNodeInfo.setCodeFlowComplexity(node, this._codeFlowComplexity);
+                AnalyzerNodeInfo.setCodeFlowComplexity(
+                    node,
+                    this._codeFlowComplexity + flowNodeCounter.getCount() * flowNodeComplexityFactor
+                );
             }
         );
 
@@ -480,6 +492,7 @@ export class Binder extends ParseTreeWalker {
                 // Create a start node for the function.
                 this._currentFlowNode = this._createStartFlowNode();
                 this._codeFlowComplexity = 0;
+                const flowNodeCounter = new FlowNodeCounter();
 
                 node.parameters.forEach((paramNode) => {
                     if (paramNode.name) {
@@ -525,7 +538,10 @@ export class Binder extends ParseTreeWalker {
                 AnalyzerNodeInfo.setAfterFlowNode(node, returnFlowNode);
 
                 AnalyzerNodeInfo.setCodeFlowExpressions(node, this._currentScopeCodeFlowExpressions!);
-                AnalyzerNodeInfo.setCodeFlowComplexity(node, this._codeFlowComplexity);
+                AnalyzerNodeInfo.setCodeFlowComplexity(
+                    node,
+                    this._codeFlowComplexity + flowNodeCounter.getCount() * flowNodeComplexityFactor
+                );
             });
         });
 

packages/pyright-internal/src/analyzer/codeFlowTypes.ts

@@ -60,6 +60,16 @@ export function getUniqueFlowNodeId() {
     return _nextFlowNodeId++;
 }
 
+export class FlowNodeCounter {
+    private _startingNodeId = _nextFlowNodeId;
+
+    // Return the number of flow nodes that have been allocated
+    // since the counter was allocated.
+    getCount() {
+        return _nextFlowNodeId - this._startingNodeId;
+    }
+}
+
 export interface FlowNode {
     flags: FlowFlags;
     id: number;