Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa1008/sa1008.go

@@ -0,0 +1,111 @@
+package sa1008
+
+import (
+	"fmt"
+	"go/ast"
+	"net/http"
+	"strconv"
+
+	"honnef.co/go/tools/analysis/code"
+	"honnef.co/go/tools/analysis/edit"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/analysis/report"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA1008",
+		Run:      run,
+		Requires: []*analysis.Analyzer{inspect.Analyzer},
+	},
+	Doc: &lint.RawDocumentation{
+		Title: `Non-canonical key in \'http.Header\' map`,
+		Text: `Keys in \'http.Header\' maps are canonical, meaning they follow a specific
+combination of uppercase and lowercase letters. Methods such as
+\'http.Header.Add\' and \'http.Header.Del\' convert inputs into this canonical
+form before manipulating the map.
+
+When manipulating \'http.Header\' maps directly, as opposed to using the
+provided methods, care should be taken to stick to canonical form in
+order to avoid inconsistencies. The following piece of code
+demonstrates one such inconsistency:
+
+    h := http.Header{}
+    h["etag"] = []string{"1234"}
+    h.Add("etag", "5678")
+    fmt.Println(h)
+
+    // Output:
+    // map[Etag:[5678] etag:[1234]]
+
+The easiest way of obtaining the canonical form of a key is to use
+\'http.CanonicalHeaderKey\'.`,
+		Since:    "2017.1",
+		Severity: lint.SeverityWarning,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+func run(pass *analysis.Pass) (any, error) {
+	fn := func(node ast.Node, push bool) bool {
+		if !push {
+			return false
+		}
+		if assign, ok := node.(*ast.AssignStmt); ok {
+			// TODO(dh): This risks missing some Header reads, for
+			// example in `h1["foo"] = h2["foo"]` – these edge
+			// cases are probably rare enough to ignore for now.
+			for _, expr := range assign.Lhs {
+				op, ok := expr.(*ast.IndexExpr)
+				if !ok {
+					continue
+				}
+				if code.IsOfTypeWithName(pass, op.X, "net/http.Header") {
+					return false
+				}
+			}
+			return true
+		}
+		op, ok := node.(*ast.IndexExpr)
+		if !ok {
+			return true
+		}
+		if !code.IsOfTypeWithName(pass, op.X, "net/http.Header") {
+			return true
+		}
+		s, ok := code.ExprToString(pass, op.Index)
+		if !ok {
+			return true
+		}
+		canonical := http.CanonicalHeaderKey(s)
+		if s == canonical {
+			return true
+		}
+		var fix analysis.SuggestedFix
+		switch op.Index.(type) {
+		case *ast.BasicLit:
+			fix = edit.Fix("Canonicalize header key", edit.ReplaceWithString(op.Index, strconv.Quote(canonical)))
+		case *ast.Ident:
+			call := &ast.CallExpr{
+				Fun:  edit.Selector("http", "CanonicalHeaderKey"),
+				Args: []ast.Expr{op.Index},
+			}
+			fix = edit.Fix("Wrap in http.CanonicalHeaderKey", edit.ReplaceWithNode(pass.Fset, op.Index, call))
+		}
+		msg := fmt.Sprintf("keys in http.Header are canonicalized, %q is not canonical; fix the constant or use http.CanonicalHeaderKey", s)
+		if fix.Message != "" {
+			report.Report(pass, op, msg, report.Fixes(fix))
+		} else {
+			report.Report(pass, op, msg)
+		}
+		return true
+	}
+	pass.ResultOf[inspect.Analyzer].(*inspector.Inspector).Nodes([]ast.Node{(*ast.AssignStmt)(nil), (*ast.IndexExpr)(nil)}, fn)
+	return nil, nil
+}