1 package sa4027
2 3 import (
4 "go/ast"
5 6 "honnef.co/go/tools/analysis/code"
7 "honnef.co/go/tools/analysis/lint"
8 "honnef.co/go/tools/analysis/report"
9 "honnef.co/go/tools/pattern"
10 11 "golang.org/x/tools/go/analysis"
12 "golang.org/x/tools/go/analysis/passes/inspect"
13 )
14 15 var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
16 Analyzer: &analysis.Analyzer{
17 Name: "SA4027",
18 Run: run,
19 Requires: []*analysis.Analyzer{inspect.Analyzer},
20 },
21 Doc: &lint.RawDocumentation{
22 Title: `\'(*net/url.URL).Query\' returns a copy, modifying it doesn't change the URL`,
23 Text: `\'(*net/url.URL).Query\' parses the current value of \'net/url.URL.RawQuery\'
24 and returns it as a map of type \'net/url.Values\'. Subsequent changes to
25 this map will not affect the URL unless the map gets encoded and
26 assigned to the URL's \'RawQuery\'.
27 28 As a consequence, the following code pattern is an expensive no-op:
29 \'u.Query().Add(key, value)\'.`,
30 Since: "2021.1",
31 Severity: lint.SeverityWarning,
32 MergeIf: lint.MergeIfAny,
33 },
34 })
35 36 var Analyzer = SCAnalyzer.Analyzer
37 38 var ineffectiveURLQueryAddQ = pattern.MustParse(`(CallExpr (SelectorExpr (CallExpr (SelectorExpr recv (Ident "Query")) []) (Ident meth)) _)`)
39 40 func run(pass *analysis.Pass) (interface{}, error) {
41 // TODO(dh): We could make this check more complex and detect
42 // pointless modifications of net/url.Values in general, but that
43 // requires us to get the state machine correct, else we'll cause
44 // false positives.
45 46 fn := func(node ast.Node) {
47 m, ok := code.Match(pass, ineffectiveURLQueryAddQ, node)
48 if !ok {
49 return
50 }
51 if !code.IsOfPointerToTypeWithName(pass, m.State["recv"].(ast.Expr), "net/url.URL") {
52 return
53 }
54 switch m.State["meth"].(string) {
55 case "Add", "Del", "Set":
56 default:
57 return
58 }
59 report.Report(pass, node, "(*net/url.URL).Query returns a copy, modifying it doesn't change the URL")
60 }
61 code.Preorder(pass, fn, (*ast.CallExpr)(nil))
62 63 return nil, nil
64 }
65