Analysis Details

Minimize the Scope of the Variables - II(Fields)

es.uniovi.reflection.analyses.cmu.dcl53

We search for fields that are unconditionally assigned before their usage, for all the methods. The rule encourages the programmer to use local variables instead.

Computational Reflection Research Group

09-30-2026 22:23

Bad Practice

Field Declaration

MATCH (cu:ORDINARY_CU)-[:DECLARES_TYPE | HAS_NESTED_TYPE]->(typeDec)-[:DECLARES_FIELD]->(attr:FIELD_DEC)
WITH cu, typeDec, attr
MATCH (attr)-[useRel:USED_BY]->(exprUse)
WITH cu, typeDec, attr, exprUse, useRel.isOwnAccess as useIsOwn
OPTIONAL MATCH (exprUse:FIELD_SELECTION)-[:IDENT_SELECTION_FROM]->(enclosingExUse)<-[:USED_BY]-(useOwnerVar)
WHERE enclosingExUse:IDENTIFIER OR enclosingExUse:IDENTIFIER_SELECTION
WITH cu, typeDec, attr, exprUse, useOwnerVar, useIsOwn, enclosingExUse
OPTIONAL MATCH (lhs)<-[:ASSIGNMENT_LHS]-(exprModif:ASSIGNMENT)-[modifRel:MODIFIED_BY]-(attr)
WHERE exprModif.position < exprUse.position
OPTIONAL MATCH (lhs:FIELD_SELECTION)-[:IDENT_SELECTION_FROM]->(enclosingExpMod), (exprModif)<-[:STATE_MODIFIED_BY]-(modifOwnerVar)
WHERE enclosingExpMod:IDENTIFIER OR enclosingExpMod:IDENTIFIER_SELECTION
WITH cu, typeDec, attr, exprUse, CASE WHEN enclosingExpMod:IDENTIFIER AND enclosingExUse:IDENTIFIER AND useOwnerVar = modifOwnerVar OR (useIsOwn AND useOwnerVar IS NULL OR useOwnerVar:THIS_REFERENCE)  AND (modifRel.isOwnAccess AND modifOwnerVar IS NULL OR modifOwnerVar:THIS_REFERENCE) THEN exprModif ELSE NULL END as exprModif
WITH cu, typeDec, attr, exprUse, es.uniovi.reflection.codeanalysis.functions.getEnclStmt(exprUse) AS useStmt, es.uniovi.reflection.codeanalysis.functions.getEnclStmt(exprModif) AS modifStmt
WITH cu, typeDec, attr, useStmt, es.uniovi.reflection.codeanalysis.functions.getEnclosingCallable(useStmt) AS useMethod, es.uniovi.reflection.codeanalysis.functions.getEnclosingCallable(modifStmt) AS modifMethod, modifStmt, exprUse
WITH cu, typeDec, attr, exprUse, useStmt, COLLECT(CASE WHEN useMethod=modifMethod THEN modifStmt ELSE NULL END) AS modifs
CALL apoc.path.subgraphNodes(useStmt, {blacklistNodes:modifs, optional:true, limit:1, labelFilter:'/CFG_START', minLevel:1, relationshipFilter:'<CFG_NEXT|<CFG_TRUE_CONDITION|<CFG_FALSE_CONDITION|<CFG_FOR_EACH_HAS_NEXT|<CFG_FOR_EACH_NO_NEXT|<CFG_IF_UNCAUGHT_EXCEPTION|<CFG_IF_NO_EXCEPTION|<CFG_IF_CAUGHT_EXCEPTION|<CFG_IF_PREVIOUS_BREAK|<CFG_IF_PREVIOUS_CONTINUE|<CFG_CASE_MATCHES|<CFG_CASE_NO_MATCH|<CFG_MAY_THROW|<CFG_THROWS'}) yield node
WITH cu, typeDec, attr, exprUse, NOT ANY(notInStmt IN COLLECT(useStmt IS NULL) WHERE notInStmt) AND SIZE(COLLECT(node))=0 AS noPathWithoutModif
WITH cu, typeDec, attr, ALL(modifBeforeUse in COLLECT(noPathWithoutModif) WHERE modifBeforeUse) as unnecessary WHERE unnecessary
RETURN '{"node":"FIELD ' + attr.actualType + ' ' + attr.name+'","line":"'+attr.lineNumber+'","column":"'+attr.column+'","rule":"CMU-DCL53","location":"'+cu.fileName+'","message":"You must minimize the scope of the variables. You can minimize the scope of attribute ' + attr.name + '(declared in line ' + attr.lineNumber + ') in class ' + typeDec.fullyQualifiedName + ' by transforming it into a local variable (as every time its value is used in a method, there is a previous unconditional assignment)."}'