cmd/vet: add hostport analyzer

+ test, release note

Fixes #28308

Change-Id: I190e2fe513eeb6b90b0398841f67bf52510b5f59
Reviewed-on: https://go-review.googlesource.com/c/go/+/667596
Auto-Submit: Alan Donovan <adonovan@google.com>
Commit-Queue: Alan Donovan <adonovan@google.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

doc/next/3-tools.md

@@ -26,10 +26,17 @@ specifying the command's current version.
 
 ### Vet {#vet}
 
+The `go vet` command includes new analyzers:
+
 <!-- go.dev/issue/18022 -->
 
-The `go vet` command now includes the
+- [waitgroup](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/waitgroup),
-[waitgroup](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/waitgroup)
+  which reports misplaced calls to [sync.WaitGroup.Add]; and
-analyzer, which reports misplaced calls to [sync.WaitGroup.Add].
 
+<!-- go.dev/issue/28308 -->
+
+- [hostport](https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/hostport),
+  which reports uses of `fmt.Sprintf("%s:%d", host, port)` to
+  construct addresses for [net.Dial], as these will not work with
+  IPv6; instead it suggests using [net.JoinHostPort].
 

src/cmd/go/internal/test/flagdefs.go

@@ -55,6 +55,7 @@ var passAnalyzersToVet = map[string]bool{
 	"directive":        true,
 	"errorsas":         true,
 	"framepointer":     true,
+	"hostport":         true,
 	"httpresponse":     true,
 	"ifaceassert":      true,
 	"loopclosure":      true,

src/cmd/go/internal/test/flagdefs_test.go

@@ -18,6 +18,9 @@ func TestMain(m *testing.M) {
 	os.Exit(m.Run())
 }
 
+// TestPassFlagToTest ensures that the generated table of flags is
+// consistent with output of "go tool vet -flags", using the installed
+// go command---so if it fails, you may need to re-run make.bash.
 func TestPassFlagToTest(t *testing.T) {
 	wantNames := genflags.ShortTestFlags()
 

src/cmd/vendor/golang.org/x/tools/go/analysis/passes/hostport/hostport.go

@@ -0,0 +1,185 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package hostport defines an analyzer for calls to net.Dial with
+// addresses of the form "%s:%d" or "%s:%s", which work only with IPv4.
+package hostport
+
+import (
+	"fmt"
+	"go/ast"
+	"go/constant"
+	"go/types"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/types/typeutil"
+	typeindexanalyzer "golang.org/x/tools/internal/analysisinternal/typeindex"
+	"golang.org/x/tools/internal/typesinternal/typeindex"
+)
+
+const Doc = `check format of addresses passed to net.Dial
+
+This analyzer flags code that produce network address strings using
+fmt.Sprintf, as in this example:
+
+    addr := fmt.Sprintf("%s:%d", host, 12345) // "will not work with IPv6"
+    ...
+    conn, err := net.Dial("tcp", addr)       // "when passed to dial here"
+
+The analyzer suggests a fix to use the correct approach, a call to
+net.JoinHostPort:
+
+    addr := net.JoinHostPort(host, "12345")
+    ...
+    conn, err := net.Dial("tcp", addr)
+
+A similar diagnostic and fix are produced for a format string of "%s:%s".
+`
+
+var Analyzer = &analysis.Analyzer{
+	Name:     "hostport",
+	Doc:      Doc,
+	URL:      "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/hostport",
+	Requires: []*analysis.Analyzer{inspect.Analyzer, typeindexanalyzer.Analyzer},
+	Run:      run,
+}
+
+func run(pass *analysis.Pass) (any, error) {
+	var (
+		index      = pass.ResultOf[typeindexanalyzer.Analyzer].(*typeindex.Index)
+		info       = pass.TypesInfo
+		fmtSprintf = index.Object("fmt", "Sprintf")
+	)
+	if !index.Used(fmtSprintf) {
+		return nil, nil // fast path: package doesn't use fmt.Sprintf
+	}
+
+	// checkAddr reports a diagnostic (and returns true) if e
+	// is a call of the form fmt.Sprintf("%d:%d", ...).
+	// The diagnostic includes a fix.
+	//
+	// dialCall is non-nil if the Dial call is non-local
+	// but within the same file.
+	checkAddr := func(e ast.Expr, dialCall *ast.CallExpr) {
+		if call, ok := e.(*ast.CallExpr); ok && typeutil.Callee(info, call) == fmtSprintf {
+			// Examine format string.
+			formatArg := call.Args[0]
+			if tv := info.Types[formatArg]; tv.Value != nil {
+				numericPort := false
+				format := constant.StringVal(tv.Value)
+				switch format {
+				case "%s:%d":
+					// Have: fmt.Sprintf("%s:%d", host, port)
+					numericPort = true
+
+				case "%s:%s":
+					// Have: fmt.Sprintf("%s:%s", host, portStr)
+					// Keep port string as is.
+
+				default:
+					return
+				}
+
+				// Use granular edits to preserve original formatting.
+				edits := []analysis.TextEdit{
+					{
+						// Replace fmt.Sprintf with net.JoinHostPort.
+						Pos:     call.Fun.Pos(),
+						End:     call.Fun.End(),
+						NewText: []byte("net.JoinHostPort"),
+					},
+					{
+						// Delete format string.
+						Pos: formatArg.Pos(),
+						End: call.Args[1].Pos(),
+					},
+				}
+
+				// Turn numeric port into a string.
+				if numericPort {
+					//  port => fmt.Sprintf("%d", port)
+					//   123 => "123"
+					port := call.Args[2]
+					newPort := fmt.Sprintf(`fmt.Sprintf("%%d", %s)`, port)
+					if port := info.Types[port].Value; port != nil {
+						if i, ok := constant.Int64Val(port); ok {
+							newPort = fmt.Sprintf(`"%d"`, i) // numeric constant
+						}
+					}
+
+					edits = append(edits, analysis.TextEdit{
+						Pos:     port.Pos(),
+						End:     port.End(),
+						NewText: []byte(newPort),
+					})
+				}
+
+				// Refer to Dial call, if not adjacent.
+				suffix := ""
+				if dialCall != nil {
+					suffix = fmt.Sprintf(" (passed to net.Dial at L%d)",
+						pass.Fset.Position(dialCall.Pos()).Line)
+				}
+
+				pass.Report(analysis.Diagnostic{
+					// Highlight the format string.
+					Pos:     formatArg.Pos(),
+					End:     formatArg.End(),
+					Message: fmt.Sprintf("address format %q does not work with IPv6%s", format, suffix),
+					SuggestedFixes: []analysis.SuggestedFix{{
+						Message:   "Replace fmt.Sprintf with net.JoinHostPort",
+						TextEdits: edits,
+					}},
+				})
+			}
+		}
+	}
+
+	// Check address argument of each call to net.Dial et al.
+	for _, callee := range []types.Object{
+		index.Object("net", "Dial"),
+		index.Object("net", "DialTimeout"),
+		index.Selection("net", "Dialer", "Dial"),
+	} {
+		for curCall := range index.Calls(callee) {
+			call := curCall.Node().(*ast.CallExpr)
+			switch address := call.Args[1].(type) {
+			case *ast.CallExpr:
+				if len(call.Args) == 2 { // avoid spread-call edge case
+					// net.Dial("tcp", fmt.Sprintf("%s:%d", ...))
+					checkAddr(address, nil)
+				}
+
+			case *ast.Ident:
+				// addr := fmt.Sprintf("%s:%d", ...)
+				// ...
+				// net.Dial("tcp", addr)
+
+				// Search for decl of addrVar within common ancestor of addrVar and Dial call.
+				// TODO(adonovan): abstract "find RHS of statement that assigns var v".
+				// TODO(adonovan): reject if there are other assignments to var v.
+				if addrVar, ok := info.Uses[address].(*types.Var); ok {
+					if curId, ok := index.Def(addrVar); ok {
+						// curIdent is the declaring ast.Ident of addr.
+						switch parent := curId.Parent().Node().(type) {
+						case *ast.AssignStmt:
+							if len(parent.Rhs) == 1 {
+								// Have: addr := fmt.Sprintf("%s:%d", ...)
+								checkAddr(parent.Rhs[0], call)
+							}
+
+						case *ast.ValueSpec:
+							if len(parent.Values) == 1 {
+								// Have: var addr = fmt.Sprintf("%s:%d", ...)
+								checkAddr(parent.Values[0], call)
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	return nil, nil
+}

src/cmd/vendor/golang.org/x/tools/internal/analysisinternal/typeindex/typeindex.go

@@ -0,0 +1,33 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package typeindex defines an analyzer that provides a
+// [golang.org/x/tools/internal/typesinternal/typeindex.Index].
+//
+// Like [golang.org/x/tools/go/analysis/passes/inspect], it is
+// intended to be used as a helper by other analyzers; it reports no
+// diagnostics of its own.
+package typeindex
+
+import (
+	"reflect"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/ast/inspector"
+	"golang.org/x/tools/internal/typesinternal/typeindex"
+)
+
+var Analyzer = &analysis.Analyzer{
+	Name: "typeindex",
+	Doc:  "indexes of type information for later passes",
+	URL:  "https://pkg.go.dev/golang.org/x/tools/internal/analysisinternal/typeindex",
+	Run: func(pass *analysis.Pass) (any, error) {
+		inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+		return typeindex.New(inspect, pass.Pkg, pass.TypesInfo), nil
+	},
+	RunDespiteErrors: true,
+	Requires:         []*analysis.Analyzer{inspect.Analyzer},
+	ResultType:       reflect.TypeOf(new(typeindex.Index)),
+}

src/cmd/vendor/golang.org/x/tools/internal/typesinternal/typeindex/typeindex.go

@@ -0,0 +1,223 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package typeindex provides an [Index] of type information for a
+// package, allowing efficient lookup of, say, whether a given symbol
+// is referenced and, if so, where from; or of the [cursor.Cursor] for
+// the declaration of a particular [types.Object] symbol.
+package typeindex
+
+import (
+	"encoding/binary"
+	"go/ast"
+	"go/types"
+	"iter"
+
+	"golang.org/x/tools/go/ast/inspector"
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/astutil/cursor"
+	"golang.org/x/tools/internal/astutil/edge"
+	"golang.org/x/tools/internal/typesinternal"
+)
+
+// New constructs an Index for the package of type-annotated syntax
+//
+// TODO(adonovan): accept a FileSet too?
+// We regret not requiring one in inspector.New.
+func New(inspect *inspector.Inspector, pkg *types.Package, info *types.Info) *Index {
+	ix := &Index{
+		inspect:  inspect,
+		info:     info,
+		packages: make(map[string]*types.Package),
+		def:      make(map[types.Object]cursor.Cursor),
+		uses:     make(map[types.Object]*uses),
+	}
+
+	addPackage := func(pkg2 *types.Package) {
+		if pkg2 != nil && pkg2 != pkg {
+			ix.packages[pkg2.Path()] = pkg2
+		}
+	}
+
+	for cur := range cursor.Root(inspect).Preorder((*ast.ImportSpec)(nil), (*ast.Ident)(nil)) {
+		switch n := cur.Node().(type) {
+		case *ast.ImportSpec:
+			// Index direct imports, including blank ones.
+			if pkgname := info.PkgNameOf(n); pkgname != nil {
+				addPackage(pkgname.Imported())
+			}
+
+		case *ast.Ident:
+			// Index all defining and using identifiers.
+			if obj := info.Defs[n]; obj != nil {
+				ix.def[obj] = cur
+			}
+
+			if obj := info.Uses[n]; obj != nil {
+				// Index indirect dependencies (via fields and methods).
+				if !typesinternal.IsPackageLevel(obj) {
+					addPackage(obj.Pkg())
+				}
+
+				us, ok := ix.uses[obj]
+				if !ok {
+					us = &uses{}
+					us.code = us.initial[:0]
+					ix.uses[obj] = us
+				}
+				delta := cur.Index() - us.last
+				if delta < 0 {
+					panic("non-monotonic")
+				}
+				us.code = binary.AppendUvarint(us.code, uint64(delta))
+				us.last = cur.Index()
+			}
+		}
+	}
+	return ix
+}
+
+// An Index holds an index mapping [types.Object] symbols to their syntax.
+// In effect, it is the inverse of [types.Info].
+type Index struct {
+	inspect  *inspector.Inspector
+	info     *types.Info
+	packages map[string]*types.Package      // packages of all symbols referenced from this package
+	def      map[types.Object]cursor.Cursor // Cursor of *ast.Ident that defines the Object
+	uses     map[types.Object]*uses         // Cursors of *ast.Idents that use the Object
+}
+
+// A uses holds the list of Cursors of Idents that use a given symbol.
+//
+// The Uses map of [types.Info] is substantial, so it pays to compress
+// its inverse mapping here, both in space and in CPU due to reduced
+// allocation. A Cursor is 2 words; a Cursor.Index is 4 bytes; but
+// since Cursors are naturally delivered in ascending order, we can
+// use varint-encoded deltas at a cost of only ~1.7-2.2 bytes per use.
+//
+// Many variables have only one or two uses, so their encoded uses may
+// fit in the 4 bytes of initial, saving further CPU and space
+// essentially for free since the struct's size class is 4 words.
+type uses struct {
+	code    []byte  // varint-encoded deltas of successive Cursor.Index values
+	last    int32   // most recent Cursor.Index value; used during encoding
+	initial [4]byte // use slack in size class as initial space for code
+}
+
+// Uses returns the sequence of Cursors of [*ast.Ident]s in this package
+// that refer to obj. If obj is nil, the sequence is empty.
+func (ix *Index) Uses(obj types.Object) iter.Seq[cursor.Cursor] {
+	return func(yield func(cursor.Cursor) bool) {
+		if uses := ix.uses[obj]; uses != nil {
+			var last int32
+			for code := uses.code; len(code) > 0; {
+				delta, n := binary.Uvarint(code)
+				last += int32(delta)
+				if !yield(cursor.At(ix.inspect, last)) {
+					return
+				}
+				code = code[n:]
+			}
+		}
+	}
+}
+
+// Used reports whether any of the specified objects are used, in
+// other words, obj != nil && Uses(obj) is non-empty for some obj in objs.
+//
+// (This treatment of nil allows Used to be called directly on the
+// result of [Index.Object] so that analyzers can conveniently skip
+// packages that don't use a symbol of interest.)
+func (ix *Index) Used(objs ...types.Object) bool {
+	for _, obj := range objs {
+		if obj != nil && ix.uses[obj] != nil {
+			return true
+		}
+	}
+	return false
+}
+
+// Def returns the Cursor of the [*ast.Ident] in this package
+// that declares the specified object, if any.
+func (ix *Index) Def(obj types.Object) (cursor.Cursor, bool) {
+	cur, ok := ix.def[obj]
+	return cur, ok
+}
+
+// Package returns the package of the specified path,
+// or nil if it is not referenced from this package.
+func (ix *Index) Package(path string) *types.Package {
+	return ix.packages[path]
+}
+
+// Object returns the package-level symbol name within the package of
+// the specified path, or nil if the package or symbol does not exist
+// or is not visible from this package.
+func (ix *Index) Object(path, name string) types.Object {
+	if pkg := ix.Package(path); pkg != nil {
+		return pkg.Scope().Lookup(name)
+	}
+	return nil
+}
+
+// Selection returns the named method or field belonging to the
+// package-level type returned by Object(path, typename).
+func (ix *Index) Selection(path, typename, name string) types.Object {
+	if obj := ix.Object(path, typename); obj != nil {
+		if tname, ok := obj.(*types.TypeName); ok {
+			obj, _, _ := types.LookupFieldOrMethod(tname.Type(), true, obj.Pkg(), name)
+			return obj
+		}
+	}
+	return nil
+}
+
+// Calls returns the sequence of cursors for *ast.CallExpr nodes that
+// call the specified callee, as defined by [typeutil.Callee].
+// If callee is nil, the sequence is empty.
+func (ix *Index) Calls(callee types.Object) iter.Seq[cursor.Cursor] {
+	return func(yield func(cursor.Cursor) bool) {
+		for cur := range ix.Uses(callee) {
+			ek, _ := cur.ParentEdge()
+
+			// The call may be of the form f() or x.f(),
+			// optionally with parens; ascend from f to call.
+			//
+			// It is tempting but wrong to use the first
+			// CallExpr ancestor: we have to make sure the
+			// ident is in the CallExpr.Fun position, otherwise
+			// f(f, f) would have two spurious matches.
+			// Avoiding Enclosing is also significantly faster.
+
+			// inverse unparen: f -> (f)
+			for ek == edge.ParenExpr_X {
+				cur = cur.Parent()
+				ek, _ = cur.ParentEdge()
+			}
+
+			// ascend selector: f -> x.f
+			if ek == edge.SelectorExpr_Sel {
+				cur = cur.Parent()
+				ek, _ = cur.ParentEdge()
+			}
+
+			// inverse unparen again
+			for ek == edge.ParenExpr_X {
+				cur = cur.Parent()
+				ek, _ = cur.ParentEdge()
+			}
+
+			// ascend from f or x.f to call
+			if ek == edge.CallExpr_Fun {
+				curCall := cur.Parent()
+				call := curCall.Node().(*ast.CallExpr)
+				if typeutil.Callee(ix.info, call) == callee {
+					if !yield(curCall) {
+						return
+					}
+				}
+			}
+		}
+	}
+}

src/cmd/vendor/modules.txt

@@ -93,6 +93,7 @@ golang.org/x/tools/go/analysis/passes/defers
 golang.org/x/tools/go/analysis/passes/directive
 golang.org/x/tools/go/analysis/passes/errorsas
 golang.org/x/tools/go/analysis/passes/framepointer
+golang.org/x/tools/go/analysis/passes/hostport
 golang.org/x/tools/go/analysis/passes/httpresponse
 golang.org/x/tools/go/analysis/passes/ifaceassert
 golang.org/x/tools/go/analysis/passes/inspect
@@ -123,6 +124,7 @@ golang.org/x/tools/go/types/objectpath
 golang.org/x/tools/go/types/typeutil
 golang.org/x/tools/internal/aliases
 golang.org/x/tools/internal/analysisinternal
+golang.org/x/tools/internal/analysisinternal/typeindex
 golang.org/x/tools/internal/astutil
 golang.org/x/tools/internal/astutil/cursor
 golang.org/x/tools/internal/astutil/edge
@@ -132,6 +134,7 @@ golang.org/x/tools/internal/fmtstr
 golang.org/x/tools/internal/stdlib
 golang.org/x/tools/internal/typeparams
 golang.org/x/tools/internal/typesinternal
+golang.org/x/tools/internal/typesinternal/typeindex
 golang.org/x/tools/internal/versions
 # rsc.io/markdown v0.0.0-20240306144322-0bf8f97ee8ef
 ## explicit; go 1.20

src/cmd/vet/main.go

@@ -24,6 +24,7 @@ import (
 	"golang.org/x/tools/go/analysis/passes/directive"
 	"golang.org/x/tools/go/analysis/passes/errorsas"
 	"golang.org/x/tools/go/analysis/passes/framepointer"
+	"golang.org/x/tools/go/analysis/passes/hostport"
 	"golang.org/x/tools/go/analysis/passes/httpresponse"
 	"golang.org/x/tools/go/analysis/passes/ifaceassert"
 	"golang.org/x/tools/go/analysis/passes/loopclosure"
@@ -67,6 +68,7 @@ func main() {
 		errorsas.Analyzer,
 		framepointer.Analyzer,
 		httpresponse.Analyzer,
+		hostport.Analyzer,
 		ifaceassert.Analyzer,
 		loopclosure.Analyzer,
 		lostcancel.Analyzer,

src/cmd/vet/testdata/hostport/hostport.go

@@ -0,0 +1,17 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This file contains tests for the hostport checker.
+
+package hostport
+
+import (
+	"fmt"
+	"net"
+)
+
+func _(host string, port int) {
+	addr := fmt.Sprintf("%s:%d", host, port) // ERROR "address format .%s:%d. does not work with IPv6"
+	net.Dial("tcp", addr)
+}

src/cmd/vet/vet_test.go

@@ -57,6 +57,7 @@ func TestVet(t *testing.T) {
 		"copylock",
 		"deadcode",
 		"directive",
+		"hostport",
 		"httpresponse",
 		"lostcancel",
 		"method",