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gopls/internal/golang: add support for variadic functions and constructors in generated tests #609

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1ba3d7b
gopls/internal/golang: support variadic functions and constructors in…
IlyasYOY Dec 5, 2025
acb706d
refactor(golang): simplify unused parameter detection and variadic ha…
IlyasYOY Dec 7, 2025
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36 changes: 31 additions & 5 deletions gopls/internal/golang/addtest.go
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Original file line number Diff line number Diff line change
Expand Up @@ -91,6 +91,7 @@ func {{.TestFuncName}}(t *{{.TestingPackageName}}.T) {
{{- if ne $index 0}}, {{end}}
{{- if .Name}}tt.{{.Name}}{{else}}{{.Value}}{{end}}
{{- end -}}
{{- if and .Receiver.Constructor.IsVariadic (not .Receiver.Constructor.IsUnusedVariadic) }}...{{- end -}}
)

{{- /* Handles the error return from constructor. */}}
Expand Down Expand Up @@ -123,6 +124,7 @@ func {{.TestFuncName}}(t *{{.TestingPackageName}}.T) {
{{- if ne $index 0}}, {{end}}
{{- if .Name}}tt.{{.Name}}{{else}}{{.Value}}{{end}}
{{- end -}}
{{- if and .Func.IsVariadic (not .Func.IsUnusedVariadic) }}...{{- end -}}
)

{{- /* Handles the returned error before the rest of return value. */}}
Expand Down Expand Up @@ -167,6 +169,12 @@ type function struct {
Name string
Args []field
Results []field
// IsVariadic holds information if the function is variadic.
// In case of the IsVariadic=true must expand it in the function-under-test call.
IsVariadic bool
// IsUnusedVariadic holds information if the function's variadic args is not used.
// In this case ... must be skipped.
IsUnusedVariadic bool
}

type receiver struct {
Expand Down Expand Up @@ -238,7 +246,7 @@ func AddTestForFunc(ctx context.Context, snapshot *cache.Snapshot, loc protocol.
extraImports = make(map[string]string) // imports to add to test file
)

var collectImports = func(file *ast.File) (map[string]string, error) {
collectImports := func(file *ast.File) (map[string]string, error) {
imps := make(map[string]string)
for _, spec := range file.Imports {
// TODO(hxjiang): support dot imports.
Expand Down Expand Up @@ -478,21 +486,31 @@ func AddTestForFunc(ctx context.Context, snapshot *cache.Snapshot, loc protocol.
PackageName: qual(pkg.Types()),
TestFuncName: testName,
Func: function{
Name: fn.Name(),
Name: fn.Name(),
IsVariadic: sig.Variadic(),
},
}

isContextType := func(t types.Type) bool {
return typesinternal.IsTypeNamed(t, "context", "Context")
}

isUnusedParameter := func(name string) bool {
return name == "" || name == "_"
}

for i := range sig.Params().Len() {
param := sig.Params().At(i)
name, typ := param.Name(), param.Type()
f := field{Type: types.TypeString(typ, qual)}
if i == 0 && isContextType(typ) {
f.Value = qual(types.NewPackage("context", "context")) + ".Background()"
} else if name == "" || name == "_" {
} else if isUnusedParameter(name) && data.Func.IsVariadic && sig.Params().Len()-1 == i {
// The last argument is the variadic argument, and it's not used in the function body,
// so we don't need to render it in the test case struct.
data.Func.IsUnusedVariadic = true
continue
} else if isUnusedParameter(name) {
f.Value, _ = typesinternal.ZeroString(typ, qual)
} else {
f.Name = name
Expand Down Expand Up @@ -619,14 +637,22 @@ func AddTestForFunc(ctx context.Context, snapshot *cache.Snapshot, loc protocol.
}

if constructor != nil {
data.Receiver.Constructor = &function{Name: constructor.Name()}
data.Receiver.Constructor = &function{
Name: constructor.Name(),
IsVariadic: constructor.Signature().Variadic(),
}
for i := range constructor.Signature().Params().Len() {
param := constructor.Signature().Params().At(i)
name, typ := param.Name(), param.Type()
f := field{Type: types.TypeString(typ, qual)}
if i == 0 && isContextType(typ) {
f.Value = qual(types.NewPackage("context", "context")) + ".Background()"
} else if name == "" || name == "_" {
} else if isUnusedParameter(name) && data.Receiver.Constructor.IsVariadic && constructor.Signature().Params().Len()-1 == i {
// The last argument is the variadic argument, and it's not used in the function body,
// so we don't need to render it in the test case struct.
data.Receiver.Constructor.IsUnusedVariadic = true
continue
} else if isUnusedParameter(name) {
f.Value, _ = typesinternal.ZeroString(typ, qual)
} else {
f.Name = name
Expand Down
179 changes: 179 additions & 0 deletions gopls/internal/test/marker/testdata/codeaction/addtest.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -1540,3 +1540,182 @@ type Foo struct {}
func NewFoo()

func (*Foo) Method[T any]() {} // no suggested fix
-- varargsinput/varargsinput.go --
package main

func Function(args ...string) (out, out1, out2 string) {return args[0], "", ""} //@codeaction("Function", "source.addTest", edit=function_varargsinput)

type Foo struct {}

func NewFoo(args ...string) (*Foo, error) {
_ = args
return nil, nil
}

func (*Foo) Method(args ...string) (out, out1, out2 string) {return args[0], "", ""} //@codeaction("Method", "source.addTest", edit=method_varargsinput)
-- varargsinput/varargsinput_test.go --
package main_test
-- @function_varargsinput/varargsinput/varargsinput_test.go --
@@ -2 +2,34 @@
+
+import (
+ "testing"
+
+ "golang.org/lsptests/addtest/varargsinput"
+)
+
+func TestFunction(t *testing.T) {
+ tests := []struct {
+ name string // description of this test case
+ // Named input parameters for target function.
+ args []string
+ want string
+ want2 string
+ want3 string
+ }{
+ // TODO: Add test cases.
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ got, got2, got3 := main.Function(tt.args...)
+ // TODO: update the condition below to compare got with tt.want.
+ if true {
+ t.Errorf("Function() = %v, want %v", got, tt.want)
+ }
+ if true {
+ t.Errorf("Function() = %v, want %v", got2, tt.want2)
+ }
+ if true {
+ t.Errorf("Function() = %v, want %v", got3, tt.want3)
+ }
+ })
+ }
+}
-- @method_varargsinput/varargsinput/varargsinput_test.go --
@@ -2 +2,40 @@
+
+import (
+ "testing"
+
+ "golang.org/lsptests/addtest/varargsinput"
+)
+
+func TestFoo_Method(t *testing.T) {
+ tests := []struct {
+ name string // description of this test case
+ // Named input parameters for receiver constructor.
+ cargs []string
+ // Named input parameters for target function.
+ args []string
+ want string
+ want2 string
+ want3 string
+ }{
+ // TODO: Add test cases.
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ f, err := main.NewFoo(tt.cargs...)
+ if err != nil {
+ t.Fatalf("could not construct receiver type: %v", err)
+ }
+ got, got2, got3 := f.Method(tt.args...)
+ // TODO: update the condition below to compare got with tt.want.
+ if true {
+ t.Errorf("Method() = %v, want %v", got, tt.want)
+ }
+ if true {
+ t.Errorf("Method() = %v, want %v", got2, tt.want2)
+ }
+ if true {
+ t.Errorf("Method() = %v, want %v", got3, tt.want3)
+ }
+ })
+ }
+}
-- unusedvarargsinput/unusedvarargsinput.go --
package main

func Function(_ ...string) (out, out1, out2 string) {return "", "", ""} //@codeaction("Function", "source.addTest", edit=function_unusedvarargsinput)

type Foo struct {}

func NewFoo(_ ...string) (*Foo, error) {
return nil, nil
}

func (*Foo) Method(_ ...string) (out, out1, out2 string) {return "", "", ""} //@codeaction("Method", "source.addTest", edit=method_unusedvarargsinput)
-- unusedvarargsinput/unusedvarargsinput_test.go --
package main_test
-- @function_unusedvarargsinput/unusedvarargsinput/unusedvarargsinput_test.go --
@@ -2 +2,32 @@
+
+import (
+ "testing"
+
+ "golang.org/lsptests/addtest/unusedvarargsinput"
+)
+
+func TestFunction(t *testing.T) {
+ tests := []struct {
+ name string // description of this test case
+ want string
+ want2 string
+ want3 string
+ }{
+ // TODO: Add test cases.
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ got, got2, got3 := main.Function()
+ // TODO: update the condition below to compare got with tt.want.
+ if true {
+ t.Errorf("Function() = %v, want %v", got, tt.want)
+ }
+ if true {
+ t.Errorf("Function() = %v, want %v", got2, tt.want2)
+ }
+ if true {
+ t.Errorf("Function() = %v, want %v", got3, tt.want3)
+ }
+ })
+ }
+}
-- @method_unusedvarargsinput/unusedvarargsinput/unusedvarargsinput_test.go --
@@ -2 +2,36 @@
+
+import (
+ "testing"
+
+ "golang.org/lsptests/addtest/unusedvarargsinput"
+)
+
+func TestFoo_Method(t *testing.T) {
+ tests := []struct {
+ name string // description of this test case
+ want string
+ want2 string
+ want3 string
+ }{
+ // TODO: Add test cases.
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ f, err := main.NewFoo()
+ if err != nil {
+ t.Fatalf("could not construct receiver type: %v", err)
+ }
+ got, got2, got3 := f.Method()
+ // TODO: update the condition below to compare got with tt.want.
+ if true {
+ t.Errorf("Method() = %v, want %v", got, tt.want)
+ }
+ if true {
+ t.Errorf("Method() = %v, want %v", got2, tt.want2)
+ }
+ if true {
+ t.Errorf("Method() = %v, want %v", got3, tt.want3)
+ }
+ })
+ }
+}