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internal/lsp: clean up some of the extract function code
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This CL creates a struct that simplifies some of the extract function
logic. Also, add a test for extraction with an underscore in the
selection (Josh mentioned that this might not work, but it seems too).

Change-Id: If917614a5824e84fb79a07def3eb75f48f10a5b9
Reviewed-on: https://go-review.googlesource.com/c/tools/+/253277
Run-TryBot: Rebecca Stambler <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Robert Findley <[email protected]>
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@stamblerre
stamblerre committed Sep 8, 2020
1 parent 93a3566 commit 77fbfae
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Showing 5 changed files with 122 additions and 65 deletions.
2 changes: 1 addition & 1 deletion internal/lsp/source/command.go
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Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,7 @@ var (
Title: "Extract to function",
suggestedFixFn: extractFunction,
appliesFn: func(fset *token.FileSet, rng span.Range, src []byte, file *ast.File, _ *types.Package, info *types.Info) bool {
_, _, _, _, _, ok, _ := canExtractFunction(fset, rng, src, file, info)
_, ok, _ := canExtractFunction(fset, rng, src, file, info)
return ok
},
}
Expand Down
156 changes: 97 additions & 59 deletions internal/lsp/source/extract.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -180,11 +180,12 @@ type returnVariable struct {
// of the function and insert this call as well as the extracted function into
// their proper locations.
func extractFunction(fset *token.FileSet, rng span.Range, src []byte, file *ast.File, pkg *types.Package, info *types.Info) (*analysis.SuggestedFix, error) {
tok, path, rng, outer, start, ok, err := canExtractFunction(fset, rng, src, file, info)
p, ok, err := canExtractFunction(fset, rng, src, file, info)
if !ok {
return nil, fmt.Errorf("extractFunction: cannot extract %s: %v",
fset.Position(rng.Start), err)
}
tok, path, rng, outer, start := p.tok, p.path, p.rng, p.outer, p.start
fileScope := info.Scopes[file]
if fileScope == nil {
return nil, fmt.Errorf("extractFunction: file scope is empty")
Expand Down Expand Up @@ -229,8 +230,10 @@ func extractFunction(fset *token.FileSet, rng span.Range, src []byte, file *ast.
// we must determine the signature of the extracted function. We will then replace
// the block with an assignment statement that calls the extracted function with
// the appropriate parameters and return values.
free, vars, assigned, defined := collectFreeVars(
info, file, fileScope, pkgScope, rng, path[0])
variables, err := collectFreeVars(info, file, fileScope, pkgScope, rng, path[0])
if err != nil {
return nil, err
}

var (
params, returns []ast.Expr // used when calling the extracted function
Expand Down Expand Up @@ -269,42 +272,38 @@ func extractFunction(fset *token.FileSet, rng span.Range, src []byte, file *ast.
// variable in the extracted function. Determine the outcome(s) for each variable
// based on whether it is free, altered within the selected block, and used outside
// of the selected block.
for _, obj := range vars {
if _, ok := seenVars[obj]; ok {
for _, v := range variables {
if _, ok := seenVars[v.obj]; ok {
continue
}
typ := analysisinternal.TypeExpr(fset, file, pkg, obj.Type())
typ := analysisinternal.TypeExpr(fset, file, pkg, v.obj.Type())
if typ == nil {
return nil, fmt.Errorf("nil AST expression for type: %v", obj.Name())
return nil, fmt.Errorf("nil AST expression for type: %v", v.obj.Name())
}
seenVars[obj] = typ
identifier := ast.NewIdent(obj.Name())
seenVars[v.obj] = typ
identifier := ast.NewIdent(v.obj.Name())
// An identifier must meet three conditions to become a return value of the
// extracted function. (1) its value must be defined or reassigned within
// the selection (isAssigned), (2) it must be used at least once after the
// selection (isUsed), and (3) its first use after the selection
// cannot be its own reassignment or redefinition (objOverriden).
if obj.Parent() == nil {
if v.obj.Parent() == nil {
return nil, fmt.Errorf("parent nil")
}
isUsed, firstUseAfter :=
objUsed(info, span.NewRange(fset, rng.End, obj.Parent().End()), obj)
_, isAssigned := assigned[obj]
_, isFree := free[obj]
if isAssigned && isUsed && !varOverridden(info, firstUseAfter, obj, isFree, outer) {
isUsed, firstUseAfter := objUsed(info, span.NewRange(fset, rng.End, v.obj.Parent().End()), v.obj)
if v.assigned && isUsed && !varOverridden(info, firstUseAfter, v.obj, v.free, outer) {
returnTypes = append(returnTypes, &ast.Field{Type: typ})
returns = append(returns, identifier)
if !isFree {
uninitialized = append(uninitialized, obj)
} else if obj.Parent().Pos() == startParent.Pos() {
if !v.free {
uninitialized = append(uninitialized, v.obj)
} else if v.obj.Parent().Pos() == startParent.Pos() {
canRedefineCount++
}
}
_, isDefined := defined[obj]
// An identifier must meet two conditions to become a parameter of the
// extracted function. (1) it must be free (isFree), and (2) its first
// use within the selection cannot be its own definition (isDefined).
if isFree && !isDefined {
if v.free && !v.defined {
params = append(params, identifier)
paramTypes = append(paramTypes, &ast.Field{
Names: []*ast.Ident{identifier},
Expand Down Expand Up @@ -409,8 +408,7 @@ func extractFunction(fset *token.FileSet, rng span.Range, src []byte, file *ast.
// statements in the selection. Update the type signature of the extracted
// function and construct the if statement that will be inserted in the enclosing
// function.
retVars, ifReturn, err = generateReturnInfo(
enclosing, pkg, path, file, info, fset, rng.Start)
retVars, ifReturn, err = generateReturnInfo(enclosing, pkg, path, file, info, fset, rng.Start)
if err != nil {
return nil, err
}
Expand Down Expand Up @@ -500,13 +498,11 @@ func extractFunction(fset *token.FileSet, rng span.Range, src []byte, file *ast.
fullReplacement.Write(newFuncBuf.Bytes()) // insert the extracted function

return &analysis.SuggestedFix{
TextEdits: []analysis.TextEdit{
{
Pos: outer.Pos(),
End: outer.End(),
NewText: []byte(fullReplacement.String()),
},
},
TextEdits: []analysis.TextEdit{{
Pos: outer.Pos(),
End: outer.End(),
NewText: []byte(fullReplacement.String()),
}},
}, nil
}

Expand Down Expand Up @@ -561,15 +557,28 @@ func findParent(start ast.Node, target ast.Node) ast.Node {
return parent
}

// variable describes the status of a variable within a selection.
type variable struct {
obj types.Object

// free reports whether the variable is a free variable, meaning it should
// be a parameter to the extracted function.
free bool

// assigned reports whether the variable is assigned to in the selection.
assigned bool

// defined reports whether the variable is defined in the selection.
defined bool
}

// collectFreeVars maps each identifier in the given range to whether it is "free."
// Given a range, a variable in that range is defined as "free" if it is declared
// outside of the range and neither at the file scope nor package scope. These free
// variables will be used as arguments in the extracted function. It also returns a
// list of identifiers that may need to be returned by the extracted function.
// Some of the code in this function has been adapted from tools/cmd/guru/freevars.go.
func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
pkgScope *types.Scope, rng span.Range, node ast.Node) (map[types.Object]struct{},
[]types.Object, map[types.Object]struct{}, map[types.Object]struct{}) {
func collectFreeVars(info *types.Info, file *ast.File, fileScope, pkgScope *types.Scope, rng span.Range, node ast.Node) ([]*variable, error) {
// id returns non-nil if n denotes an object that is referenced by the span
// and defined either within the span or in the lexical environment. The bool
// return value acts as an indicator for where it was defined.
Expand Down Expand Up @@ -612,7 +621,7 @@ func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
}
return nil, false
}
free := make(map[types.Object]struct{})
seen := make(map[types.Object]*variable)
firstUseIn := make(map[types.Object]token.Pos)
var vars []types.Object
ast.Inspect(node, func(n ast.Node) bool {
Expand All @@ -630,15 +639,16 @@ func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
prune = true
}
if obj != nil {
if isFree {
free[obj] = struct{}{}
seen[obj] = &variable{
obj: obj,
free: isFree,
}
vars = append(vars, obj)
// Find the first time that the object is used in the selection.
first, ok := firstUseIn[obj]
if !ok || n.Pos() < first {
firstUseIn[obj] = n.Pos()
}
vars = append(vars, obj)
if prune {
return false
}
Expand All @@ -657,8 +667,6 @@ func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
// 3: y := 3
// 4: z := x + a
//
assigned := make(map[types.Object]struct{})
defined := make(map[types.Object]struct{})
ast.Inspect(node, func(n ast.Node) bool {
if n == nil {
return false
Expand All @@ -677,7 +685,10 @@ func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
if obj == nil {
continue
}
assigned[obj] = struct{}{}
if _, ok := seen[obj]; !ok {
continue
}
seen[obj].assigned = true
if n.Tok != token.DEFINE {
continue
}
Expand All @@ -697,7 +708,10 @@ func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
if referencesObj(info, expr, obj) {
continue
}
defined[obj] = struct{}{}
if _, ok := seen[obj]; !ok {
continue
}
seen[obj].defined = true
break
}
}
Expand All @@ -717,7 +731,10 @@ func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
if obj == nil {
continue
}
assigned[obj] = struct{}{}
if _, ok := seen[obj]; !ok {
continue
}
seen[obj].assigned = true
}
}
return false
Expand All @@ -727,12 +744,23 @@ func collectFreeVars(info *types.Info, file *ast.File, fileScope *types.Scope,
} else if obj, _ := id(ident); obj == nil {
return false
} else {
assigned[obj] = struct{}{}
if _, ok := seen[obj]; !ok {
return false
}
seen[obj].assigned = true
}
}
return true
})
return free, vars, assigned, defined
var variables []*variable
for _, obj := range vars {
v, ok := seen[obj]
if !ok {
return nil, fmt.Errorf("no seen types.Object for %v", obj)
}
variables = append(variables, v)
}
return variables, nil
}

// referencesObj checks whether the given object appears in the given expression.
Expand All @@ -756,29 +784,34 @@ func referencesObj(info *types.Info, expr ast.Expr, obj types.Object) bool {
return hasObj
}

// canExtractFunction reports whether the code in the given range can be extracted to a function.
func canExtractFunction(fset *token.FileSet, rng span.Range, src []byte, file *ast.File, info *types.Info) (*token.File, []ast.Node, span.Range, *ast.FuncDecl, ast.Node, bool, error) {
type fnExtractParams struct {
tok *token.File
path []ast.Node
rng span.Range
outer *ast.FuncDecl
start ast.Node
}

// canExtractFunction reports whether the code in the given range can be
// extracted to a function.
func canExtractFunction(fset *token.FileSet, rng span.Range, src []byte, file *ast.File, info *types.Info) (*fnExtractParams, bool, error) {
if rng.Start == rng.End {
return nil, nil, span.Range{}, nil, nil, false,
fmt.Errorf("start and end are equal")
return nil, false, fmt.Errorf("start and end are equal")
}
tok := fset.File(file.Pos())
if tok == nil {
return nil, nil, span.Range{}, nil, nil, false,
fmt.Errorf("no file for pos %v", fset.Position(file.Pos()))
return nil, false, fmt.Errorf("no file for pos %v", fset.Position(file.Pos()))
}
rng = adjustRangeForWhitespace(rng, tok, src)
path, _ := astutil.PathEnclosingInterval(file, rng.Start, rng.End)
if len(path) == 0 {
return nil, nil, span.Range{}, nil, nil, false,
fmt.Errorf("no path enclosing interval")
return nil, false, fmt.Errorf("no path enclosing interval")
}
// Node that encloses the selection must be a statement.
// TODO: Support function extraction for an expression.
_, ok := path[0].(ast.Stmt)
if !ok {
return nil, nil, span.Range{}, nil, nil, false,
fmt.Errorf("node is not a statement")
return nil, false, fmt.Errorf("node is not a statement")
}

// Find the function declaration that encloses the selection.
Expand All @@ -790,7 +823,7 @@ func canExtractFunction(fset *token.FileSet, rng span.Range, src []byte, file *a
}
}
if outer == nil {
return nil, nil, span.Range{}, nil, nil, false, fmt.Errorf("no enclosing function")
return nil, false, fmt.Errorf("no enclosing function")
}

// Find the nodes at the start and end of the selection.
Expand All @@ -799,8 +832,8 @@ func canExtractFunction(fset *token.FileSet, rng span.Range, src []byte, file *a
if n == nil {
return false
}
// Do not override 'start' with a node that begins at the same location but is
// nested further from 'outer'.
// Do not override 'start' with a node that begins at the same location
// but is nested further from 'outer'.
if start == nil && n.Pos() == rng.Start && n.End() <= rng.End {
start = n
}
Expand All @@ -810,10 +843,15 @@ func canExtractFunction(fset *token.FileSet, rng span.Range, src []byte, file *a
return n.Pos() <= rng.End
})
if start == nil || end == nil {
return nil, nil, span.Range{}, nil, nil, false,
fmt.Errorf("range does not map to AST nodes")
return nil, false, fmt.Errorf("range does not map to AST nodes")
}
return tok, path, rng, outer, start, true, nil
return &fnExtractParams{
tok: tok,
path: path,
rng: rng,
outer: outer,
start: start,
}, true, nil
}

// objUsed checks if the object is used within the range. It returns the first occurence of
Expand Down
5 changes: 3 additions & 2 deletions internal/lsp/testdata/lsp/primarymod/extract/extract_function/extract_args_returns.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ func _() {
a = 5 //@mark(exSt0, "a")
a = a + 2 //@mark(exEn0, "2")
//@extractfunc(exSt0, exEn0)
b := a * 2
_ = 3 + 4
b := a * 2 //@mark(exB, " b")
_ = 3 + 4 //@mark(exEnd, "4")
//@extractfunc(exB, exEnd)
}
22 changes: 20 additions & 2 deletions internal/lsp/testdata/lsp/primarymod/extract/extract_function/extract_args_returns.go.golden
View file
Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,9 @@ func _() {
a := 1
a = fn0(a) //@mark(exEn0, "2")
//@extractfunc(exSt0, exEn0)
b := a * 2
_ = 3 + 4
b := a * 2 //@mark(exB, " b")
_ = 3 + 4 //@mark(exEnd, "4")
//@extractfunc(exB, exEnd)
}

func fn0(a int) int {
Expand All @@ -15,3 +16,20 @@ func fn0(a int) int {
return a
}

-- functionextraction_extract_args_returns_8_1 --
package extract

func _() {
a := 1
a = 5 //@mark(exSt0, "a")
a = a + 2 //@mark(exEn0, "2")
//@extractfunc(exSt0, exEn0)
fn0(a) //@mark(exEnd, "4")
//@extractfunc(exB, exEnd)
}

func fn0(a int) {
b := a * 2
_ = 3 + 4
}

2 changes: 1 addition & 1 deletion internal/lsp/testdata/lsp/summary.txt.golden
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@ FoldingRangesCount = 2
FormatCount = 6
ImportCount = 8
SuggestedFixCount = 38
FunctionExtractionCount = 11
FunctionExtractionCount = 12
DefinitionsCount = 63
TypeDefinitionsCount = 2
HighlightsCount = 69
Expand Down

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