Skip to content

Commit

Permalink
feat: support for Java.NullPointerException
Browse files Browse the repository at this point in the history
  • Loading branch information
@nedpals
nedpals committed Dec 30, 2023
1 parent c7dad23 commit 0e4a013
Show file tree
Hide file tree
Showing 3 changed files with 119 additions and 66 deletions.
2 changes: 2 additions & 0 deletions error_templates/java/java.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -78,6 +78,8 @@ func getDefaultValueForType(sym lib.Symbol) string {
return "0"
case java.BuiltinTypes.FloatingPoint.DoubleSymbol:
return "0.0"
case java.BuiltinTypes.StringSymbol:
return "\"example\""
default:
return "null"
}
Expand Down
159 changes: 102 additions & 57 deletions error_templates/java/null_pointer_exception.go
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,8 @@
package java

import (
"context"
"fmt"
"strings"

lib "github.com/nedpals/errgoengine"
"github.com/nedpals/errgoengine/languages/java"
Expand All @@ -10,86 +11,92 @@ import (
type exceptionLocationKind int

const (
fromUnknown exceptionLocationKind = 0
fromFunctionArgument exceptionLocationKind = iota
fromSystemOut exceptionLocationKind = iota
fromArrayAccess exceptionLocationKind = iota
fromExpression exceptionLocationKind = iota
fromMethodInvocation exceptionLocationKind = iota
fromUnknown exceptionLocationKind = iota
fromFunctionArgument
fromSystemOut
fromArrayAccess
fromExpression
fromMethodInvocation
fromAssignment
)

type nullPointerExceptionCtx struct {
kind exceptionLocationKind
// symbolInvolved lib.SyntaxNode
methodName string
origin string
parent lib.SyntaxNode
}

// TODO: unit testing
var NullPointerException = lib.ErrorTemplate{
Name: "NullPointerException",
Pattern: runtimeErrorPattern("java.lang.NullPointerException", ""),
OnAnalyzeErrorFn: func(cd *lib.ContextData, err *lib.MainError) {
OnAnalyzeErrorFn: func(cd *lib.ContextData, m *lib.MainError) {
ctx := nullPointerExceptionCtx{}

// if the offending line is an offending method call, get the argument that triggered the null error
if cd.MainError.Nearest.Type() == "expression_statement" {
exprNode := cd.MainError.Nearest.NamedChild(0)
// NOTE: i hope we will be able to parse the entire
// java system library without hardcoding the definitions lol
for q := m.Nearest.Query(`([
(field_access object: (_) @ident field: (identifier))
(method_invocation object: [
(identifier) @ident
(field_access object: (_) @obj field: (identifier)) @ident
]) @call
(method_invocation arguments: (argument_list (identifier) @ident))
(array_access) @access
]
(#any-match? @obj "^[a-z0-9_]+")
(#not-match? @ident "^[A-Z][a-z0-9_]$"))`); q.Next(); {
tagName := q.CurrentTagName()
node := q.CurrentNode()

// NOTE: i hope we will be able to parse the entire
// java system library without hardcoding the definitions lol
if exprNode.Type() == "method_invocation" {
objNode := exprNode.ChildByFieldName("object")
// check if this is just simple printing
if objNode.Text() == "System.out" {
if tagName == "call" {
if strings.HasPrefix(node.Text(), "System.out.") {
ctx.kind = fromSystemOut
} else if retType := cd.Analyzer.AnalyzeNode(context.Background(), exprNode); retType == java.BuiltinTypes.NullSymbol {
cd.MainError.Nearest = exprNode
ctx.kind = fromMethodInvocation
} else {
// use the next node tagged with "ident"
continue
}
} else if tagName == "access" {
cd.MainError.Nearest = node
ctx.kind = fromArrayAccess
} else if tagName == "ident" {
retType := lib.UnwrapActualReturnType(cd.FindSymbol(node.Text(), node.StartPosition().Index))
if retType != java.BuiltinTypes.NullSymbol {
continue
}

if objNode.Type() == "array_access" {
// inArray = true
cd.MainError.Nearest = exprNode
ctx.kind = fromArrayAccess
} else {
arguments := exprNode.ChildByFieldName("arguments")
for i := 0; i < int(arguments.NamedChildCount()); i++ {
argNode := arguments.NamedChild(i)
retType := cd.Analyzer.AnalyzeNode(context.Background(), argNode)

if retType == java.BuiltinTypes.NullSymbol || argNode.Type() == "array_access" {
cd.MainError.Nearest = argNode
ctx.kind = fromFunctionArgument
break
}
}
ctx.origin = node.Text()
parent := node.Parent()
switch parent.Type() {
case "field_access":
ctx.kind = fromExpression
case "argument_list":
// if the offending line is an offending method call, get the argument that triggered the null error
ctx.kind = fromFunctionArgument
case "method_invocation":
ctx.kind = fromMethodInvocation
ctx.methodName = parent.ChildByFieldName("name").Text()
ctx.origin = parent.ChildByFieldName("object").Text()
case "assignment_expression":
ctx.kind = fromAssignment
}
} else if exprNode.Type() == "assignment_expression" {
// right := exprNode.ChildByFieldName("right")
//
}

// identify the *MAIN* culprit
mainNode := cd.MainError.Nearest
switch mainNode.Type() {
case "method_invocation":
nameNode := mainNode.ChildByFieldName("name")
ctx.methodName = nameNode.Text()
ctx.origin = mainNode.ChildByFieldName("object").Text()
default:
ctx.origin = mainNode.Text()
ctx.parent = parent
m.Nearest = node
break
}

err.Context = ctx
}

m.Context = ctx
},
OnGenExplainFn: func(cd *lib.ContextData, gen *lib.ExplainGenerator) {
// TODO: create a function that will find the node with a null return type
ctx := cd.MainError.Context.(nullPointerExceptionCtx)

if ctx.kind == fromSystemOut {
gen.Add("Your program tried to print the value of ")
gen.Add("The error occurs due to your program tried to print the value of ")
if len(ctx.methodName) != 0 {
gen.Add("\"%s\" method from ", ctx.methodName)
}
Expand All @@ -99,20 +106,58 @@ var NullPointerException = lib.ErrorTemplate{
// if inArray {
// gen.Add("Your program tried to execute the \"%s\" method from \"%s\" which is a null.", )
// } else {
gen.Add("Your program tried to execute the \"%s\" method from \"%s\" which is a null.", ctx.methodName, ctx.origin)
gen.Add("The error occurs due to your program tried to execute the \"%s\" method from \"%s\" which is a null.", ctx.methodName, ctx.origin)
// }
return
}

gen.Add("Your program try to access or manipulate an object reference that is currently pointing to `null`, meaning it doesn't refer to any actual object in memory. This typically happens when you forget to initialize an object before using it, or when you try to access an object that hasn't been properly assigned a value. ")
},
OnGenBugFixFn: func(cd *lib.ContextData, gen *lib.BugFixGenerator) {
gen.Add("Wrap with an if statement", func(s *lib.BugFixSuggestion) {
s.AddDescription("Check for the variable that is being used as `null`.")
})
ctx := cd.MainError.Context.(nullPointerExceptionCtx)
parent := ctx.parent
for parent.Type() != "expression_statement" {
if parent.Parent().IsNull() {
break
}
parent = parent.Parent()
}

if parent.Type() == "expression_statement" {
spaces := cd.MainError.Document.LineAt(parent.StartPosition().Line)[:parent.StartPosition().Column]

gen.Add("Wrap with an if statement", func(s *lib.BugFixSuggestion) {
s.AddStep("Check for the variable that is being used as `null`.").
AddFix(lib.FixSuggestion{
NewText: fmt.Sprintf("if (%s != null) {\n", ctx.origin) + strings.Repeat(spaces, 2),
StartPosition: parent.StartPosition(),
EndPosition: parent.StartPosition(),
}).
AddFix(lib.FixSuggestion{
NewText: "\n" + spaces + "}\n",
StartPosition: parent.EndPosition(),
EndPosition: parent.EndPosition(),
})
})
}

gen.Add("Initialize the variable", func(s *lib.BugFixSuggestion) {
s.AddDescription("An alternative fix is to initialize the `test` variable with a non-null value before calling the method.")
// get the original location of variable
symbolTree := cd.InitOrGetSymbolTree(cd.MainDocumentPath())
varSym := symbolTree.GetSymbolByNode(cd.MainError.Nearest)

loc := varSym.Location()
varDeclNode := cd.MainError.Document.RootNode().NamedDescendantForPointRange(loc)
if varDeclNode.Type() == "variable_declarator" {
loc = varDeclNode.ChildByFieldName("value").Location()
}

s.AddStep("An alternative fix is to initialize the `%s` variable with a non-null value before calling the method.", ctx.origin).
AddFix(lib.FixSuggestion{
NewText: getDefaultValueForType(lib.UnwrapReturnType(varSym)),
StartPosition: loc.StartPos,
EndPosition: loc.EndPos,
})
})
},
}
24 changes: 15 additions & 9 deletions error_templates/java/test_files/null_pointer_exception/test.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ Exception in thread "main" java.lang.NullPointerException
template: "Java.NullPointerException"
---
# NullPointerException
This error occurs because the program is trying to access a method or property of a null object, in this case, trying to invoke the `toUpperCase()` method on a `null` string.
The error occurs due to your program tried to execute the "toUpperCase" method from "test" which is a null.
```
String test = null;
System.out.println(test.toUpperCase());
Expand All @@ -18,17 +18,23 @@ This error occurs because the program is trying to access a method or property o
### 1. Wrap with an if statement
Check for the variable that is being used as `null`.
```diff
String test = null;
- System.out.println(test.toUpperCase());
+ if (test != null) {
+ System.out.println(test.toUpperCase());
+ }
public static void main(String args[]) {
String test = null;
- System.out.println(test.toUpperCase());
+ if (test != null) {
+ System.out.println(test.toUpperCase());
+ }
}
}
```

### 2. Initialize the variable
An alternative fix is to initialize the `test` variable with a non-null value before calling the method.
```diff
- String test = null;
+ String test = "example"; // Assign a non-null value
System.out.println(test.toUpperCase());
public class ShouldBeNull {
public static void main(String args[]) {
- String test = null;
+ String test = "example";
System.out.println(test.toUpperCase());
}
```

0 comments on commit 0e4a013

Please sign in to comment.