warn/warn_bazel_api.go

// Warnings for incompatible changes in the Bazel API

package warn

import (
	"fmt"
	"sort"

	"github.com/bazelbuild/buildtools/build"
	"github.com/bazelbuild/buildtools/bzlenv"
	"github.com/bazelbuild/buildtools/edit"
	"github.com/bazelbuild/buildtools/tables"
)

// Bazel API-specific warnings

var functionsWithPositionalArguments = map[string]bool{
	"distribs":            true,
	"exports_files":       true,
	"licenses":            true,
	"print":               true,
	"register_toolchains": true,
	"vardef":              true,
}

// negateExpression returns an expression which is a negation of the input.
// If it's a boolean literal (true or false), just return the opposite literal.
// If it's a unary expression with a unary `not` operator, just remove it.
// Otherwise, insert a `not` operator.
// It's assumed that input is no longer needed as it may be mutated or reused by the function.
func negateExpression(expr build.Expr) build.Expr {
	paren, ok := expr.(*build.ParenExpr)
	if ok {
		newParen := *paren
		newParen.X = negateExpression(paren.X)
		return &newParen
	}

	unary, ok := expr.(*build.UnaryExpr)
	if ok && unary.Op == "not" {
		return unary.X
	}

	boolean, ok := expr.(*build.Ident)
	if ok {
		newBoolean := *boolean
		if boolean.Name == "True" {
			newBoolean.Name = "False"
		} else {
			newBoolean.Name = "True"
		}
		return &newBoolean
	}

	return &build.UnaryExpr{
		Op: "not",
		X:  expr,
	}
}

// getParam search for a param with a given name in a given list of function arguments
// and returns it with its index
func getParam(attrs []build.Expr, paramName string) (int, *build.Ident, *build.AssignExpr) {
	for i, attr := range attrs {
		as, ok := attr.(*build.AssignExpr)
		if !ok {
			continue
		}
		name, ok := (as.LHS).(*build.Ident)
		if !ok || name.Name != paramName {
			continue
		}
		return i, name, as
	}
	return -1, nil, nil
}

// isFunctionCall checks whether expr is a call of a function with a given name
func isFunctionCall(expr build.Expr, name string) (*build.CallExpr, bool) {
	call, ok := expr.(*build.CallExpr)
	if !ok {
		return nil, false
	}
	if ident, ok := call.X.(*build.Ident); ok && ident.Name == name {
		return call, true
	}
	return nil, false
}

// globalVariableUsageCheck checks whether there's a usage of a given global variable in the file.
// It's ok to shadow the name with a local variable and use it.
func globalVariableUsageCheck(f *build.File, global, alternative string) []*LinterFinding {
	var findings []*LinterFinding

	if f.Type != build.TypeBzl {
		return findings
	}

	var walk func(e *build.Expr, env *bzlenv.Environment)
	walk = func(e *build.Expr, env *bzlenv.Environment) {
		defer bzlenv.WalkOnceWithEnvironment(*e, env, walk)

		ident, ok := (*e).(*build.Ident)
		if !ok {
			return
		}
		if ident.Name != global {
			return
		}
		if binding := env.Get(ident.Name); binding != nil {
			return
		}

		// Fix
		newIdent := *ident
		newIdent.Name = alternative

		findings = append(findings, makeLinterFinding(ident,
			fmt.Sprintf(`Global variable %q is deprecated in favor of %q. Please rename it.`, global, alternative),
			LinterReplacement{e, &newIdent}))
	}
	var expr build.Expr = f
	walk(&expr, bzlenv.NewEnvironment())

	return findings
}

// insertLoad returns a *LinterReplacement object representing a replacement required for inserting
// an additional load statement. Returns nil if nothing needs to be changed.
func insertLoad(f *build.File, module string, symbols []string) *LinterReplacement {
	// Try to find an existing load statement
	for i, stmt := range f.Stmt {
		load, ok := stmt.(*build.LoadStmt)
		if !ok || load.Module.Value != module {
			continue
		}

		// Modify an existing load statement
		newLoad := *load
		if !edit.AppendToLoad(&newLoad, symbols, symbols) {
			return nil
		}
		return &LinterReplacement{&(f.Stmt[i]), &newLoad}
	}

	// Need to insert a new load statement. Can't modify the tree here, so just insert a placeholder
	// nil statement and return a replacement for it.
	i := 0
	for i = range f.Stmt {
		stmt := f.Stmt[i]
		_, isComment := stmt.(*build.CommentBlock)
		_, isString := stmt.(*build.StringExpr)
		isDocString := isString && i == 0
		if !isComment && !isDocString {
			// Insert a nil statement here
			break
		}
	}
	stmts := append([]build.Expr{}, f.Stmt[:i]...)
	stmts = append(stmts, nil)
	stmts = append(stmts, f.Stmt[i:]...)
	f.Stmt = stmts

	return &LinterReplacement{&(f.Stmt[i]), edit.NewLoad(module, symbols, symbols)}
}

func notLoadedFunctionUsageCheckInternal(expr *build.Expr, env *bzlenv.Environment, globals []string, loadFrom string) ([]string, []*LinterFinding) {
	var loads []string
	var findings []*LinterFinding

	call, ok := (*expr).(*build.CallExpr)
	if !ok {
		return loads, findings
	}

	var name string
	var replacements []LinterReplacement
	switch node := call.X.(type) {
	case *build.DotExpr:
		// Maybe native.`global`?
		ident, ok := node.X.(*build.Ident)
		if !ok || ident.Name != "native" {
			return loads, findings
		}

		name = node.Name
		// Replace `native.foo()` with `foo()`
		newCall := *call
		newCall.X = &build.Ident{Name: node.Name}
		replacements = append(replacements, LinterReplacement{expr, &newCall})
	case *build.Ident:
		// Maybe `global`()?
		if binding := env.Get(node.Name); binding != nil {
			return loads, findings
		}
		name = node.Name
	default:
		return loads, findings
	}

	for _, global := range globals {
		if name == global {
			loads = append(loads, name)
			findings = append(findings,
				makeLinterFinding(call.X, fmt.Sprintf(`Function %q is not global anymore and needs to be loaded from %q.`, global, loadFrom), replacements...))
			break
		}
	}

	return loads, findings
}

func notLoadedSymbolUsageCheckInternal(expr *build.Expr, env *bzlenv.Environment, globals []string, loadFrom string) ([]string, []*LinterFinding) {
	var loads []string
	var findings []*LinterFinding

	ident, ok := (*expr).(*build.Ident)
	if !ok {
		return loads, findings
	}
	if binding := env.Get(ident.Name); binding != nil {
		return loads, findings
	}

	for _, global := range globals {
		if ident.Name == global {
			loads = append(loads, ident.Name)
			findings = append(findings,
				makeLinterFinding(ident, fmt.Sprintf(`Symbol %q is not global anymore and needs to be loaded from %q.`, global, loadFrom)))
			break
		}
	}

	return loads, findings
}

// notLoadedUsageCheck checks whether there's a usage of a given not imported function or symbol in the file
// and adds a load statement if necessary.
func notLoadedUsageCheck(f *build.File, functions, symbols []string, loadFrom string) []*LinterFinding {
	toLoad := make(map[string]bool)
	var findings []*LinterFinding

	var walk func(expr *build.Expr, env *bzlenv.Environment)
	walk = func(expr *build.Expr, env *bzlenv.Environment) {
		defer bzlenv.WalkOnceWithEnvironment(*expr, env, walk)

		functionLoads, functionFindings := notLoadedFunctionUsageCheckInternal(expr, env, functions, loadFrom)
		findings = append(findings, functionFindings...)
		for _, load := range functionLoads {
			toLoad[load] = true
		}

		symbolLoads, symbolFindings := notLoadedSymbolUsageCheckInternal(expr, env, symbols, loadFrom)
		findings = append(findings, symbolFindings...)
		for _, load := range symbolLoads {
			toLoad[load] = true
		}
	}
	var expr build.Expr = f
	walk(&expr, bzlenv.NewEnvironment())

	if len(toLoad) == 0 {
		return nil
	}

	loads := []string{}
	for l := range toLoad {
		loads = append(loads, l)
	}

	sort.Strings(loads)
	replacement := insertLoad(f, loadFrom, loads)
	if replacement != nil {
		// Add the same replacement to all relevant findings.
		for _, f := range findings {
			f.Replacement = append(f.Replacement, *replacement)
		}
	}

	return findings
}

// notLoadedFunctionUsageCheck checks whether there's a usage of a given not imported function in the file
// and adds a load statement if necessary.
func NotLoadedFunctionUsageCheck(f *build.File, globals []string, loadFrom string) []*LinterFinding {
	return notLoadedUsageCheck(f, globals, []string{}, loadFrom)
}

// makePositional makes the function argument positional (removes the keyword if it exists)
func makePositional(argument build.Expr) build.Expr {
	if binary, ok := argument.(*build.AssignExpr); ok {
		return binary.RHS
	}
	return argument
}

// makeKeyword makes the function argument keyword (adds or edits the keyword name)
func makeKeyword(argument build.Expr, name string) build.Expr {
	assign, ok := argument.(*build.AssignExpr)
	if !ok {
		return &build.AssignExpr{
			LHS: &build.Ident{Name: name},
			Op:  "=",
			RHS: argument,
		}
	}
	ident, ok := assign.LHS.(*build.Ident)
	if ok && ident.Name == name {
		// Nothing to change
		return argument
	}

	// Technically it's possible that the LHS is not an ident, but that is a syntax error anyway.
	newAssign := *assign
	newAssign.LHS = &build.Ident{Name: name}
	return &newAssign
}

func attrConfigurationWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	build.WalkPointers(f, func(expr *build.Expr, stack []build.Expr) {
		// Find nodes that match the following pattern: attr.xxxx(..., cfg = "data", ...)
		call, ok := (*expr).(*build.CallExpr)
		if !ok {
			return
		}
		dot, ok := (call.X).(*build.DotExpr)
		if !ok {
			return
		}
		base, ok := dot.X.(*build.Ident)
		if !ok || base.Name != "attr" {
			return
		}
		i, _, param := getParam(call.List, "cfg")
		if param == nil {
			return
		}
		value, ok := (param.RHS).(*build.StringExpr)
		if !ok || value.Value != "data" {
			return
		}
		newCall := *call
		newCall.List = append(newCall.List[:i], newCall.List[i+1:]...)

		findings = append(findings,
			makeLinterFinding(param, `cfg = "data" for attr definitions has no effect and should be removed.`,
				LinterReplacement{expr, &newCall}))
	})
	return findings
}

func attrNonEmptyWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	build.WalkPointers(f, func(expr *build.Expr, stack []build.Expr) {
		// Find nodes that match the following pattern: attr.xxxx(..., non_empty = ..., ...)
		call, ok := (*expr).(*build.CallExpr)
		if !ok {
			return
		}
		dot, ok := (call.X).(*build.DotExpr)
		if !ok {
			return
		}
		base, ok := dot.X.(*build.Ident)
		if !ok || base.Name != "attr" {
			return
		}
		_, name, param := getParam(call.List, "non_empty")
		if param == nil {
			return
		}

		// Fix
		newName := *name
		newName.Name = "allow_empty"
		negatedRHS := negateExpression(param.RHS)

		findings = append(findings,
			makeLinterFinding(param, "non_empty attributes for attr definitions are deprecated in favor of allow_empty.",
				LinterReplacement{&param.LHS, &newName},
				LinterReplacement{&param.RHS, negatedRHS},
			))
	})
	return findings
}

func attrSingleFileWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	build.WalkPointers(f, func(expr *build.Expr, stack []build.Expr) {
		// Find nodes that match the following pattern: attr.xxxx(..., single_file = ..., ...)
		call, ok := (*expr).(*build.CallExpr)
		if !ok {
			return
		}
		dot, ok := (call.X).(*build.DotExpr)
		if !ok {
			return
		}
		base, ok := dot.X.(*build.Ident)
		if !ok || base.Name != "attr" {
			return
		}
		singleFileIndex, singleFileKw, singleFileParam := getParam(call.List, "single_file")
		if singleFileParam == nil {
			return
		}

		// Fix
		newCall := *call
		newCall.List = append([]build.Expr{}, call.List...)

		newSingleFileKw := *singleFileKw
		newSingleFileKw.Name = "allow_single_file"
		singleFileValue := singleFileParam.RHS

		if boolean, ok := singleFileValue.(*build.Ident); ok && boolean.Name == "False" {
			// if the value is `False`, just remove the whole parameter
			newCall.List = append(newCall.List[:singleFileIndex], newCall.List[singleFileIndex+1:]...)
		} else {
			// search for `allow_files` parameter in the same attr definition and remove it
			allowFileIndex, _, allowFilesParam := getParam(call.List, "allow_files")
			if allowFilesParam != nil {
				singleFileValue = allowFilesParam.RHS
				newCall.List = append(newCall.List[:allowFileIndex], newCall.List[allowFileIndex+1:]...)
				if singleFileIndex > allowFileIndex {
					singleFileIndex--
				}
			}
		}
		findings = append(findings,
			makeLinterFinding(singleFileParam, "single_file is deprecated in favor of allow_single_file.",
				LinterReplacement{expr, &newCall},
				LinterReplacement{&singleFileParam.LHS, &newSingleFileKw},
				LinterReplacement{&singleFileParam.RHS, singleFileValue},
			))
	})
	return findings
}

func ctxActionsWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	build.WalkPointers(f, func(expr *build.Expr, stack []build.Expr) {
		// Find nodes that match the following pattern: ctx.xxxx(...)
		call, ok := (*expr).(*build.CallExpr)
		if !ok {
			return
		}
		dot, ok := (call.X).(*build.DotExpr)
		if !ok {
			return
		}
		base, ok := dot.X.(*build.Ident)
		if !ok || base.Name != "ctx" {
			return
		}

		switch dot.Name {
		case "new_file", "experimental_new_directory", "file_action", "action", "empty_action", "template_action":
			// fix
		default:
			return
		}

		// Fix
		newCall := *call
		newCall.List = append([]build.Expr{}, call.List...)
		newDot := *dot
		newCall.X = &newDot

		switch dot.Name {
		case "new_file":
			if len(call.List) > 2 {
				// Can't fix automatically because the new API doesn't support the 3 arguments signature
				findings = append(findings,
					makeLinterFinding(dot, fmt.Sprintf(`"ctx.new_file" is deprecated in favor of "ctx.actions.declare_file".`)))
				return
			}
			newDot.Name = "actions.declare_file"
			if len(call.List) == 2 {
				// swap arguments:
				// ctx.new_file(sibling, name) -> ctx.actions.declare_file(name, sibling=sibling)
				newCall.List[0], newCall.List[1] = makePositional(call.List[1]), makeKeyword(call.List[0], "sibling")
			}
		case "experimental_new_directory":
			newDot.Name = "actions.declare_directory"
		case "file_action":
			newDot.Name = "actions.write"
			i, ident, param := getParam(newCall.List, "executable")
			if ident != nil {
				newIdent := *ident
				newIdent.Name = "is_executable"
				newParam := *param
				newParam.LHS = &newIdent
				newCall.List[i] = &newParam
			}
		case "action":
			newDot.Name = "actions.run"
			if _, _, command := getParam(call.List, "command"); command != nil {
				newDot.Name = "actions.run_shell"
			}
		case "empty_action":
			newDot.Name = "actions.do_nothing"
		case "template_action":
			newDot.Name = "actions.expand_template"
			if i, ident, param := getParam(call.List, "executable"); ident != nil {
				newIdent := *ident
				newIdent.Name = "is_executable"
				newParam := *param
				newParam.LHS = &newIdent
				newCall.List[i] = &newParam
			}
		}

		findings = append(findings, makeLinterFinding(dot,
			fmt.Sprintf(`"ctx.%s" is deprecated in favor of "ctx.%s".`, dot.Name, newDot.Name),
			LinterReplacement{expr, &newCall}))
	})
	return findings
}

func fileTypeWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	var walk func(e *build.Expr, env *bzlenv.Environment)
	walk = func(e *build.Expr, env *bzlenv.Environment) {
		defer bzlenv.WalkOnceWithEnvironment(*e, env, walk)

		call, ok := isFunctionCall(*e, "FileType")
		if !ok {
			return
		}
		if binding := env.Get("FileType"); binding == nil {
			findings = append(findings,
				makeLinterFinding(call, "The FileType function is deprecated."))
		}
	}
	var expr build.Expr = f
	walk(&expr, bzlenv.NewEnvironment())

	return findings
}

func packageNameWarning(f *build.File) []*LinterFinding {
	return globalVariableUsageCheck(f, "PACKAGE_NAME", "native.package_name()")
}

func repositoryNameWarning(f *build.File) []*LinterFinding {
	return globalVariableUsageCheck(f, "REPOSITORY_NAME", "native.repository_name()")
}

func outputGroupWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	build.WalkPointers(f, func(expr *build.Expr, stack []build.Expr) {
		// Find nodes that match the following pattern: ctx.attr.xxx.output_group
		outputGroup, ok := (*expr).(*build.DotExpr)
		if !ok || outputGroup.Name != "output_group" {
			return
		}
		dep, ok := (outputGroup.X).(*build.DotExpr)
		if !ok {
			return
		}
		attr, ok := (dep.X).(*build.DotExpr)
		if !ok || attr.Name != "attr" {
			return
		}
		ctx, ok := (attr.X).(*build.Ident)
		if !ok || ctx.Name != "ctx" {
			return
		}

		// Replace `xxx.output_group` with `xxx[OutputGroupInfo]`
		findings = append(findings,
			makeLinterFinding(outputGroup,
				`"ctx.attr.dep.output_group" is deprecated in favor of "ctx.attr.dep[OutputGroupInfo]".`,
				LinterReplacement{expr, &build.IndexExpr{
					X: dep,
					Y: &build.Ident{Name: "OutputGroupInfo"},
				},
				}))
	})
	return findings
}

func nativeGitRepositoryWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}
	return NotLoadedFunctionUsageCheck(f, []string{"git_repository", "new_git_repository"}, "@bazel_tools//tools/build_defs/repo:git.bzl")
}

func nativeHTTPArchiveWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}
	return NotLoadedFunctionUsageCheck(f, []string{"http_archive"}, "@bazel_tools//tools/build_defs/repo:http.bzl")
}

func nativeAndroidRulesWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl && f.Type != build.TypeBuild {
		return nil
	}
	return NotLoadedFunctionUsageCheck(f, tables.AndroidNativeRules, tables.AndroidLoadPath)
}

func nativeCcRulesWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl && f.Type != build.TypeBuild {
		return nil
	}
	return NotLoadedFunctionUsageCheck(f, tables.CcNativeRules, tables.CcLoadPath)
}

func nativeJavaRulesWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl && f.Type != build.TypeBuild {
		return nil
	}
	return NotLoadedFunctionUsageCheck(f, tables.JavaNativeRules, tables.JavaLoadPath)
}

func nativePyRulesWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl && f.Type != build.TypeBuild {
		return nil
	}
	return NotLoadedFunctionUsageCheck(f, tables.PyNativeRules, tables.PyLoadPath)
}

func nativeProtoRulesWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl && f.Type != build.TypeBuild {
		return nil
	}
	return notLoadedUsageCheck(f, tables.ProtoNativeRules, tables.ProtoNativeSymbols, tables.ProtoLoadPath)
}

func contextArgsAPIWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	types := detectTypes(f)

	build.WalkPointers(f, func(expr *build.Expr, stack []build.Expr) {
		// Search for `<ctx.actions.args>.add()` nodes
		call, ok := (*expr).(*build.CallExpr)
		if !ok {
			return
		}
		dot, ok := call.X.(*build.DotExpr)
		if !ok || dot.Name != "add" || types[dot.X] != CtxActionsArgs {
			return
		}

		// If neither before_each nor join_with nor map_fn is specified, the node is ok.
		// Otherwise if join_with is specified, use `.add_joined` instead.
		// Otherwise use `.add_all` instead.

		_, beforeEachKw, beforeEach := getParam(call.List, "before_each")
		_, _, joinWith := getParam(call.List, "join_with")
		_, mapFnKw, mapFn := getParam(call.List, "map_fn")
		if beforeEach == nil && joinWith == nil && mapFn == nil {
			// No deprecated API detected
			return
		}

		// Fix
		var replacements []LinterReplacement

		newDot := *dot
		newDot.Name = "add_all"
		replacements = append(replacements, LinterReplacement{&call.X, &newDot})

		if joinWith != nil {
			newDot.Name = "add_joined"
			if beforeEach != nil {
				// `add_joined` doesn't have a `before_each` parameter, replace it with `format_each`:
				// `before_each = foo` -> `format_each = foo + "%s"`
				newBeforeEachKw := *beforeEachKw
				newBeforeEachKw.Name = "format_each"

				replacements = append(replacements, LinterReplacement{&beforeEach.LHS, &newBeforeEachKw})
				replacements = append(replacements, LinterReplacement{&beforeEach.RHS, &build.BinaryExpr{
					X:  beforeEach.RHS,
					Op: "+",
					Y:  &build.StringExpr{Value: "%s"},
				}})
			}
		}
		if mapFnKw != nil {
			// Replace `map_fn = ...` with `map_each = ...`
			newMapFnKw := *mapFnKw
			newMapFnKw.Name = "map_each"
			replacements = append(replacements, LinterReplacement{&mapFn.LHS, &newMapFnKw})
		}

		findings = append(findings,
			makeLinterFinding(call,
				`"ctx.actions.args().add()" for multiple arguments is deprecated in favor of "add_all()" or "add_joined()".`,
				replacements...))

	})
	return findings
}

func attrOutputDefaultWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	build.Walk(f, func(expr build.Expr, stack []build.Expr) {
		// Find nodes that match the following pattern: attr.output(..., default = ...)
		call, ok := expr.(*build.CallExpr)
		if !ok {
			return
		}
		dot, ok := (call.X).(*build.DotExpr)
		if !ok || dot.Name != "output" {
			return
		}
		base, ok := dot.X.(*build.Ident)
		if !ok || base.Name != "attr" {
			return
		}
		_, _, param := getParam(call.List, "default")
		if param == nil {
			return
		}
		findings = append(findings,
			makeLinterFinding(param, `The "default" parameter for attr.output() is deprecated.`))
	})
	return findings
}

func attrLicenseWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding
	build.Walk(f, func(expr build.Expr, stack []build.Expr) {
		// Find nodes that match the following pattern: attr.license(...)
		call, ok := expr.(*build.CallExpr)
		if !ok {
			return
		}
		dot, ok := (call.X).(*build.DotExpr)
		if !ok || dot.Name != "license" {
			return
		}
		base, ok := dot.X.(*build.Ident)
		if !ok || base.Name != "attr" {
			return
		}
		findings = append(findings,
			makeLinterFinding(expr, `"attr.license()" is deprecated and shouldn't be used.`))
	})
	return findings
}

// ruleImplReturnWarning checks whether a rule implementation function returns an old-style struct
func ruleImplReturnWarning(f *build.File) []*LinterFinding {
	if f.Type != build.TypeBzl {
		return nil
	}

	var findings []*LinterFinding

	// iterate over rules and collect rule implementation function names
	implNames := make(map[string]bool)
	build.Walk(f, func(expr build.Expr, stack []build.Expr) {
		call, ok := isFunctionCall(expr, "rule")
		if !ok {
			return
		}

		// Try to get the implementaton parameter either by name or as the first argument
		var impl build.Expr
		_, _, param := getParam(call.List, "implementation")
		if param != nil {
			impl = param.RHS
		} else if len(call.List) > 0 {
			impl = call.List[0]
		}
		if name, ok := impl.(*build.Ident); ok {
			implNames[name.Name] = true
		}
	})

	// iterate over functions
	for _, stmt := range f.Stmt {
		def, ok := stmt.(*build.DefStmt)
		if !ok || !implNames[def.Name] {
			// either not a function or not used in the file as a rule implementation function
			continue
		}
		// traverse the function and find all of its return statements
		build.Walk(def, func(expr build.Expr, stack []build.Expr) {
			ret, ok := expr.(*build.ReturnStmt)
			if !ok {
				return
			}
			// check whether it returns a struct
			if _, ok := isFunctionCall(ret.Result, "struct"); ok {
				findings = append(findings, makeLinterFinding(ret, `Avoid using the legacy provider syntax.`))
			}
		})
	}

	return findings
}

type signature struct {
	Positional []string // These parameters are typePositional-only
	Keyword    []string // These parameters are typeKeyword-only
}

var signatures = map[string]signature{
	"all":     {[]string{"elements"}, []string{}},
	"any":     {[]string{"elements"}, []string{}},
	"tuple":   {[]string{"x"}, []string{}},
	"list":    {[]string{"x"}, []string{}},
	"len":     {[]string{"x"}, []string{}},
	"str":     {[]string{"x"}, []string{}},
	"repr":    {[]string{"x"}, []string{}},
	"bool":    {[]string{"x"}, []string{}},
	"int":     {[]string{"x"}, []string{}},
	"dir":     {[]string{"x"}, []string{}},
	"type":    {[]string{"x"}, []string{}},
	"hasattr": {[]string{"x", "name"}, []string{}},
	"getattr": {[]string{"x", "name", "default"}, []string{}},
	"select":  {[]string{"x"}, []string{}},
	"glob":    {[]string{"include"}, []string{"exclude", "exclude_directories"}},
}

// functionName returns the name of the given function if it's a direct function call (e.g.
// `foo(...)` or `native.foo(...)`, but not `foo.bar(...)` or `x[3](...)`
func functionName(call *build.CallExpr) (string, bool) {
	if ident, ok := call.X.(*build.Ident); ok {
		return ident.Name, true
	}
	// Also check for `native.<name>`
	dot, ok := call.X.(*build.DotExpr)
	if !ok {
		return "", false
	}
	if ident, ok := dot.X.(*build.Ident); !ok || ident.Name != "native" {
		return "", false
	}
	return dot.Name, true
}

const (
	typePositional int = iota
	typeKeyword
	typeArgs
	typeKwargs
)

// paramType returns the type of the param. If it's a typeKeyword param, also returns its name
func paramType(param build.Expr) (int, string) {
	switch param := param.(type) {
	case *build.AssignExpr:
		if param.Op == "=" {
			ident, ok := param.LHS.(*build.Ident)
			if ok {
				return typeKeyword, ident.Name
			}
			return typeKeyword, ""
		}
	case *build.UnaryExpr:
		switch param.Op {
		case "*":
			return typeArgs, ""
		case "**":
			return typeKwargs, ""
		}
	}
	return typePositional, ""
}

// keywordPositionalParametersWarning checks for deprecated typeKeyword parameters of builtins
func keywordPositionalParametersWarning(f *build.File) []*LinterFinding {
	var findings []*LinterFinding

	// Check for legacy typeKeyword parameters
	build.WalkPointers(f, func(expr *build.Expr, stack []build.Expr) {
		call, ok := (*expr).(*build.CallExpr)
		if !ok || len(call.List) == 0 {
			return
		}
		function, ok := functionName(call)
		if !ok {
			return
		}

		// Findings and replacements for the current call expression
		var callFindings []*LinterFinding
		var callReplacements []LinterReplacement

		signature, ok := signatures[function]
		if !ok {
			return
		}

		var paramTypes []int // types of the parameters (typeKeyword or not) after the replacements has been applied.
		for i, parameter := range call.List {
			pType, name := paramType(parameter)
			paramTypes = append(paramTypes, pType)

			if pType == typeKeyword && i < len(signature.Positional) && signature.Positional[i] == name {
				// The parameter should be typePositional
				callFindings = append(callFindings, makeLinterFinding(
					parameter,
					fmt.Sprintf(`Keyword parameter %q for %q should be positional.`, signature.Positional[i], function),
				))
				callReplacements = append(callReplacements, LinterReplacement{&call.List[i], makePositional(parameter)})
				paramTypes[i] = typePositional
			}

			if pType == typePositional && i >= len(signature.Positional) && i < len(signature.Positional)+len(signature.Keyword) {
				// The parameter should be typeKeyword
				keyword := signature.Keyword[i-len(signature.Positional)]
				callFindings = append(callFindings, makeLinterFinding(
					parameter,
					fmt.Sprintf(`Parameter at the position %d for %q should be keyword (%s = ...).`, i+1, function, keyword),
				))
				callReplacements = append(callReplacements, LinterReplacement{&call.List[i], makeKeyword(parameter, keyword)})
				paramTypes[i] = typeKeyword
			}
		}

		if len(callFindings) == 0 {
			return
		}

		// Only apply the replacements if the signature is correct after they have been applied
		// (i.e. the order of the parameters is typePositional, typeKeyword, typeArgs, typeKwargs)
		// Otherwise the signature will be not correct, probably it was incorrect initially.
		// All the replacements should be applied to the first finding for the current node.

		if sort.IntsAreSorted(paramTypes) {
			// It's possible that the parameter list had `ForceCompact` set to true because it only contained
			// positional arguments, and now it has keyword arguments as well. Reset the flag to let the
			// printer decide how the function call should be formatted.
			for _, t := range paramTypes {
				if t == typeKeyword {
					// There's at least one keyword argument
					newCall := *call
					newCall.ForceCompact = false
					callFindings[0].Replacement = append(callFindings[0].Replacement, LinterReplacement{expr, &newCall})
					break
				}
			}
			// Attach all the parameter replacements to the first finding
			callFindings[0].Replacement = append(callFindings[0].Replacement, callReplacements...)
		}

		findings = append(findings, callFindings...)
	})

	return findings
}