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

05-08-2024 22:58

Bad Practice

Field Definition

MATCH (cu:COMPILATION_UNIT)-[:HAS_INNER_TYPE_DEF | HAS_TYPE_DEF]->(typeDec)-[:DECLARES_FIELD]->(attr:ATTR_DEF)
WITH distinct cu,typeDec,attr
MATCH (attr)-[:USED_BY]->(exprUse)
WITH distinct cu,typeDec,attr,exprUse
OPTIONAL MATCH (exprUse:MEMBER_SELECTION)-[:MEMBER_SELECT_EXPR]->(memberOwner:IDENTIFIER)<-[:USED_BY]-(useOwnerVar)
WITH distinct cu,typeDec,attr,exprUse,useOwnerVar,memberOwner
OPTIONAL MATCH (lhs)<-[:ASSIGNMENT_LHS]-(exprModif:ASSIGNMENT)<-[:MODIFIED_BY]-(attr)
WHERE exprModif.lineNumber<=exprUse.lineNumber
OPTIONAL MATCH(lhs:MEMBER_SELECTION)-[:MEMBER_SELECT_EXPR]->(memberOwner:IDENTIFIER),(exprModif)<-[:STATE_MODIFIED_BY]-(modifOwnerVar)
WITH distinct cu,typeDec,attr,useOwnerVar,modifOwnerVar,memberOwner,exprModif,exprUse
WHERE exprModif IS NULL OR useOwnerVar=modifOwnerVar OR (memberOwner IS NULL OR useOwnerVar:THIS_REF) AND (modifOwnerVar:THIS_REF OR modifOwnerVar IS NULL)
WITH DISTINCT  cu,typeDec,attr,es.uniovi.reflection.codeanalysis.functions.getEnclosingStmt(exprUse) as useStmt,es.uniovi.reflection.codeanalysis.functions.getEnclosingStmt(exprModif) as modifStmt 
WITH cu,typeDec,attr,useStmt,es.uniovi.reflection.codeanalysis.functions.getEnclosingMethod(useStmt) as useMethod,es.uniovi.reflection.codeanalysis.functions.getEnclosingMethod(modifStmt) as modifMethod,modifStmt
WITH DISTINCT cu,typeDec,attr,useStmt,useMethod, CASE WHEN useMethod=modifMethod THEN modifStmt ELSE NULL END as modifStmt
WITH cu,typeDec,attr,useStmt,COLLECT(modifStmt) as modifs, useMethod
CALL apoc.path.subgraphNodes(useStmt,{blacklistNodes:modifs,optional:true,limit:1,labelFilter:'/CFG_ENTRY',minLevel:1,relationshipFilter:'<CFG_NEXT_STATEMENT|<CFG_NEXT_STATEMENT_IF_TRUE|<CFG_NEXT_STATEMENT_IF_FALSE|<CFG_FOR_EACH_HAS_NEXT|<CFG_FOR_EACH_NO_MORE_ELEMENTS|<CFG_IF_THERE_IS_UNCAUGHT_EXCEPTION|<CFG_NO_EXCEPTION|<CFG_CAUGHT_EXCEPTION|<CFG_AFTER_FINALLY_PREVIOUS_BREAK|<CFG_AFTER_FINALLY_PREVIOUS_CONTINUE|<CFG_SWITCH_CASE_IS_EQUAL_TO|<CFG_SWITCH_DEFAULT_CASE|<CFG_MAY_THROW|<CFG_THROWS|<TRY_CATCH'}) yield node
WITH cu,typeDec,attr,useStmt,useMethod,COLLECT(node) as pathsWithNoModifs, modifs
WITH DISTINCT cu,typeDec,attr, COLLECT(useMethod:CALLABLE_DEF AND SIZE(pathsWithNoModifs)=0) as existsPathsWithNoModifs
WHERE ALL(existsPath IN existsPathsWithNoModifs WHERE existsPath)
RETURN '{"rule":"CMU-DCL53","location":"' + cu.fileName + '","node":"ATTR DEF ' + attr.actualType + ' ' + attr.name + '","line":"' + attr.lineNumber + '","column":"' + attr.column + '","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)"}'