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gopls/internal/lsp/source/completion: support postfix completion (iferr,
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variferr)

Go require explicit error handle, you must check and return error
after some function call. These postfix completion can help to write
the check error code.

The postfix completion iferr replace
  strconv.Atoi("32").iferr
to
  if _, err := strconv.Atoi("32"); err != nil {
    return zero1, zero2, err
  }
The postfix completion variferr replace
  strconv.Atoi("32").variferr
to
  value, err := strconv.Atoi("32");
  if err != nil {
    return zero1, zero2, err
  }
The "zero1", "zero2" represent the zero value of enclosed function
results.

Fixes golang/go#64178

Change-Id: I8313168514bfdfd22ad03b0228d4ca738ba9e9e3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/550455
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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@rogeryk @gopherbot
rogeryk authored and gopherbot committed Jan 10, 2024
1 parent 581c0b3 commit 706525d
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Showing 4 changed files with 217 additions and 13 deletions.
165 changes: 152 additions & 13 deletions gopls/internal/lsp/source/completion/postfix_snippets.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -68,13 +68,18 @@ type postfixTmplArgs struct {
// Type is the type of "foo.bar" in "foo.bar.print!".
Type types.Type

// FuncResult are results of the enclosed function
FuncResults []*types.Var

sel *ast.SelectorExpr
scope *types.Scope
snip snippet.Builder
importIfNeeded func(pkgPath string, scope *types.Scope) (name string, edits []protocol.TextEdit, err error)
edits []protocol.TextEdit
qf types.Qualifier
varNames map[string]bool
placeholders bool
currentTabStop int
}

var postfixTmpls = []postfixTmpl{{
Expand Down Expand Up @@ -250,26 +255,119 @@ if {{.X}} != nil {
body: `{{if (eq .Kind "slice" "map" "array" "chan") -}}
len({{.X}})
{{- end}}`,
}, {
label: "iferr",
details: "check error and return",
body: `{{if and .StmtOK (eq (.TypeName .Type) "error") -}}
{{- $errName := (or (and .IsIdent .X) "err") -}}
if {{if not .IsIdent}}err := {{.X}}; {{end}}{{$errName}} != nil {
return {{$a := .}}{{range $i, $v := .FuncResults}}
{{- if $i}}, {{end -}}
{{- if eq ($a.TypeName $v.Type) "error" -}}
{{$a.Placeholder $errName}}
{{- else -}}
{{$a.Zero $v.Type}}
{{- end -}}
{{end}}
}
{{end}}`,
}, {
label: "iferr",
details: "check error and return",
body: `{{if and .StmtOK (eq .Kind "tuple") (len .Tuple) (eq (.TypeName .TupleLast.Type) "error") -}}
{{- $a := . -}}
if {{range $i, $v := .Tuple}}{{if $i}}, {{end}}{{if and (eq ($a.TypeName $v.Type) "error") (eq (inc $i) (len $a.Tuple))}}err{{else}}_{{end}}{{end}} := {{.X -}}
; err != nil {
return {{range $i, $v := .FuncResults}}
{{- if $i}}, {{end -}}
{{- if eq ($a.TypeName $v.Type) "error" -}}
{{$a.Placeholder "err"}}
{{- else -}}
{{$a.Zero $v.Type}}
{{- end -}}
{{end}}
}
{{end}}`,
}, {
// variferr snippets use nested placeholders, as described in
// https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#snippet_syntax,
// so that users can wrap the returned error without modifying the error
// variable name.
label: "variferr",
details: "assign variables and check error",
body: `{{if and .StmtOK (eq .Kind "tuple") (len .Tuple) (eq (.TypeName .TupleLast.Type) "error") -}}
{{- $a := . -}}
{{- $errName := "err" -}}
{{- range $i, $v := .Tuple -}}
{{- if $i}}, {{end -}}
{{- if and (eq ($a.TypeName $v.Type) "error") (eq (inc $i) (len $a.Tuple)) -}}
{{$errName | $a.SpecifiedPlaceholder (len $a.Tuple)}}
{{- else -}}
{{$a.VarName $v.Type $v.Name | $a.Placeholder}}
{{- end -}}
{{- end}} := {{.X}}
if {{$errName | $a.SpecifiedPlaceholder (len $a.Tuple)}} != nil {
return {{range $i, $v := .FuncResults}}
{{- if $i}}, {{end -}}
{{- if eq ($a.TypeName $v.Type) "error" -}}
{{$errName | $a.SpecifiedPlaceholder (len $a.Tuple) |
$a.SpecifiedPlaceholder (inc (len $a.Tuple))}}
{{- else -}}
{{$a.Zero $v.Type}}
{{- end -}}
{{end}}
}
{{end}}`,
}, {
label: "variferr",
details: "assign variables and check error",
body: `{{if and .StmtOK (eq (.TypeName .Type) "error") -}}
{{- $a := . -}}
{{- $errName := .VarName nil "err" -}}
{{$errName | $a.SpecifiedPlaceholder 1}} := {{.X}}
if {{$errName | $a.SpecifiedPlaceholder 1}} != nil {
return {{range $i, $v := .FuncResults}}
{{- if $i}}, {{end -}}
{{- if eq ($a.TypeName $v.Type) "error" -}}
{{$errName | $a.SpecifiedPlaceholder 1 | $a.SpecifiedPlaceholder 2}}
{{- else -}}
{{$a.Zero $v.Type}}
{{- end -}}
{{end}}
}
{{end}}`,
}}

// Cursor indicates where the client's cursor should end up after the
// snippet is done.
func (a *postfixTmplArgs) Cursor() string {
a.snip.WriteFinalTabstop()
return ""
return "$0"
}

// Placeholder indicate a tab stops with the placeholder string, the order
// Placeholder indicate a tab stop with the placeholder string, the order
// of tab stops is the same as the order of invocation
func (a *postfixTmplArgs) Placeholder(s string) string {
if a.placeholders {
a.snip.WritePlaceholder(func(b *snippet.Builder) {
b.WriteText(s)
})
} else {
a.snip.WritePlaceholder(nil)
func (a *postfixTmplArgs) Placeholder(placeholder string) string {
if !a.placeholders {
placeholder = ""
}
return fmt.Sprintf("${%d:%s}", a.nextTabStop(), placeholder)
}

// nextTabStop returns the next tab stop index for a new placeholder.
func (a *postfixTmplArgs) nextTabStop() int {
// Tab stops start from 1, so increment before returning.
a.currentTabStop++
return a.currentTabStop
}

// SpecifiedPlaceholder indicate a specified tab stop with the placeholder string.
// Sometimes the same tab stop appears in multiple places and their numbers
// need to be specified. e.g. variferr
func (a *postfixTmplArgs) SpecifiedPlaceholder(tabStop int, placeholder string) string {
if !a.placeholders {
placeholder = ""
}
return ""
return fmt.Sprintf("${%d:%s}", tabStop, placeholder)
}

// Import makes sure the package corresponding to path is imported,
Expand Down Expand Up @@ -309,7 +407,7 @@ func (a *postfixTmplArgs) KeyType() types.Type {
return a.Type.Underlying().(*types.Map).Key()
}

// Tuple returns the tuple result vars if X is a call expression.
// Tuple returns the tuple result vars if the type of X is tuple.
func (a *postfixTmplArgs) Tuple() []*types.Var {
tuple, _ := a.Type.(*types.Tuple)
if tuple == nil {
Expand All @@ -323,6 +421,18 @@ func (a *postfixTmplArgs) Tuple() []*types.Var {
return typs
}

// TupleLast returns the last tuple result vars if the type of X is tuple.
func (a *postfixTmplArgs) TupleLast() *types.Var {
tuple, _ := a.Type.(*types.Tuple)
if tuple == nil {
return nil
}
if tuple.Len() == 0 {
return nil
}
return tuple.At(tuple.Len() - 1)
}

// TypeName returns the textual representation of type t.
func (a *postfixTmplArgs) TypeName(t types.Type) (string, error) {
if t == nil || t == types.Typ[types.Invalid] {
Expand All @@ -331,6 +441,16 @@ func (a *postfixTmplArgs) TypeName(t types.Type) (string, error) {
return types.TypeString(t, a.qf), nil
}

// Zero return the zero value representation of type t
func (a *postfixTmplArgs) Zero(t types.Type) string {
return formatZeroValue(t, a.qf)
}

func (a *postfixTmplArgs) IsIdent() bool {
_, ok := a.sel.X.(*ast.Ident)
return ok
}

// VarName returns a suitable variable name for the type t. If t
// implements the error interface, "err" is used. If t is not a named
// type then nonNamedDefault is used. Otherwise a name is made by
Expand Down Expand Up @@ -417,6 +537,17 @@ func (c *completer) addPostfixSnippetCandidates(ctx context.Context, sel *ast.Se
}
}

var funcResults []*types.Var
if c.enclosingFunc != nil {
results := c.enclosingFunc.sig.Results()
if results != nil {
funcResults = make([]*types.Var, results.Len())
for i := 0; i < results.Len(); i++ {
funcResults[i] = results.At(i)
}
}
}

scope := c.pkg.GetTypes().Scope().Innermost(c.pos)
if scope == nil {
return
Expand Down Expand Up @@ -455,6 +586,8 @@ func (c *completer) addPostfixSnippetCandidates(ctx context.Context, sel *ast.Se
StmtOK: stmtOK,
Obj: exprObj(c.pkg.GetTypesInfo(), sel.X),
Type: selType,
FuncResults: funcResults,
sel: sel,
qf: c.qf,
importIfNeeded: c.importIfNeeded,
scope: scope,
Expand Down Expand Up @@ -497,7 +630,9 @@ func initPostfixRules() {
var idx int
for _, rule := range postfixTmpls {
var err error
rule.tmpl, err = template.New("postfix_snippet").Parse(rule.body)
rule.tmpl, err = template.New("postfix_snippet").Funcs(template.FuncMap{
"inc": inc,
}).Parse(rule.body)
if err != nil {
log.Panicf("error parsing postfix snippet template: %v", err)
}
Expand All @@ -508,6 +643,10 @@ func initPostfixRules() {
})
}

func inc(i int) int {
return i + 1
}

// importIfNeeded returns the package identifier and any necessary
// edits to import package pkgPath.
func (c *completer) importIfNeeded(pkgPath string, scope *types.Scope) (string, []protocol.TextEdit, error) {
Expand Down
2 changes: 2 additions & 0 deletions gopls/internal/test/integration/completion/postfix_snippet_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -306,6 +306,7 @@ func _() {
${1:}, ${2:} := foo()
}
`,
allowMultipleItem: true,
},
{
name: "var_single_value",
Expand All @@ -318,6 +319,7 @@ func _() {
foo().var
}
`,
allowMultipleItem: true,
after: `
package foo
Expand Down
33 changes: 33 additions & 0 deletions gopls/internal/test/marker/testdata/completion/postfix.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,10 @@ go 1.18
-- postfix.go --
package snippets

import (
"strconv"
)

func _() {
var foo []int
foo.append //@rank(" //", postfixAppend)
Expand Down Expand Up @@ -96,3 +100,32 @@ func _() {
foo.fo //@snippet(" //", postfixForChannel, "for ${1:} := range foo {\n\t$0\n}")
foo.rang //@snippet(" //", postfixRangeChannel, "for ${1:} := range foo {\n\t$0\n}")
}

type T struct {
Name string
}

func _() (string, T, map[string]string, error) {
/* iferr! */ //@item(postfixIfErr, "iferr!", "check error and return", "snippet")
/* variferr! */ //@item(postfixVarIfErr, "variferr!", "assign variables and check error", "snippet")
/* var! */ //@item(postfixVars, "var!", "assign to variables", "snippet")

strconv.Atoi("32"). //@complete(" //", postfixIfErr, postfixPrint, postfixVars, postfixVarIfErr)

var err error
err.iferr //@snippet(" //", postfixIfErr, "if err != nil {\n\treturn \"\", T{}, nil, ${1:}\n}\n")

strconv.Atoi("32").iferr //@snippet(" //", postfixIfErr, "if _, err := strconv.Atoi(\"32\"); err != nil {\n\treturn \"\", T{}, nil, ${1:}\n}\n")

strconv.Atoi("32").variferr //@snippet(" //", postfixVarIfErr, "${1:}, ${2:} := strconv.Atoi(\"32\")\nif ${2:} != nil {\n\treturn \"\", T{}, nil, ${3:}\n}\n")

// test function return multiple errors
var foo func() (error, error)
foo().iferr //@snippet(" //", postfixIfErr, "if _, err := foo(); err != nil {\n\treturn \"\", T{}, nil, ${1:}\n}\n")
foo().variferr //@snippet(" //", postfixVarIfErr, "${1:}, ${2:} := foo()\nif ${2:} != nil {\n\treturn \"\", T{}, nil, ${3:}\n}\n")

// test function just return error
var bar func() error
bar().iferr //@snippet(" //", postfixIfErr, "if err := bar(); err != nil {\n\treturn \"\", T{}, nil, ${1:}\n}\n")
bar().variferr //@snippet(" //", postfixVarIfErr, "${1:} := bar()\nif ${1:} != nil {\n\treturn \"\", T{}, nil, ${2:}\n}\n")
}
30 changes: 30 additions & 0 deletions gopls/internal/test/marker/testdata/completion/postfix_placeholder.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,10 @@ go 1.18
-- postfix.go --
package snippets

import (
"strconv"
)

func _() {
/* for! */ //@item(postfixFor, "for!", "range over slice by index", "snippet")
/* forr! */ //@item(postfixForr, "forr!", "range over slice by index and value", "snippet")
Expand Down Expand Up @@ -51,3 +55,29 @@ func _() {
foo.fo //@snippet(" //", postfixForChannel, "for ${1:e} := range foo {\n\t$0\n}")
foo.rang //@snippet(" //", postfixRangeChannel, "for ${1:e} := range foo {\n\t$0\n}")
}

type T struct {
Name string
}

func _() (string, T, map[string]string, error) {
/* iferr! */ //@item(postfixIfErr, "iferr!", "check error and return", "snippet")
/* variferr! */ //@item(postfixVarIfErr, "variferr!", "assign variables and check error", "snippet")
/* var! */ //@item(postfixVars, "var!", "assign to variables", "snippet")


var err error
err.iferr //@snippet(" //", postfixIfErr, "if err != nil {\n\treturn \"\", T{}, nil, ${1:err}\n}\n")
strconv.Atoi("32").iferr //@snippet(" //", postfixIfErr, "if _, err := strconv.Atoi(\"32\"); err != nil {\n\treturn \"\", T{}, nil, ${1:err}\n}\n")
strconv.Atoi("32").variferr //@snippet(" //", postfixVarIfErr, "${1:i}, ${2:err} := strconv.Atoi(\"32\")\nif ${2:err} != nil {\n\treturn \"\", T{}, nil, ${3:${2:err}}\n}\n")

// test function return multiple errors
var foo func() (error, error)
foo().iferr //@snippet(" //", postfixIfErr, "if _, err := foo(); err != nil {\n\treturn \"\", T{}, nil, ${1:err}\n}\n")
foo().variferr //@snippet(" //", postfixVarIfErr, "${1:err2}, ${2:err} := foo()\nif ${2:err} != nil {\n\treturn \"\", T{}, nil, ${3:${2:err}}\n}\n")

// test function just return error
var bar func() error
bar().iferr //@snippet(" //", postfixIfErr, "if err := bar(); err != nil {\n\treturn \"\", T{}, nil, ${1:err}\n}\n")
bar().variferr //@snippet(" //", postfixVarIfErr, "${1:err2} := bar()\nif ${1:err2} != nil {\n\treturn \"\", T{}, nil, ${2:${1:err2}}\n}\n")
}

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