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text/template: clarify error when too few or too many return values

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Prior to CL 561115, calling a function without any return values would
print "function called with 0 args; should be 1 or 2". Afterwards, the
error message became "too many return values".

Keep the improvement of referring to return values rather than args,
and bring back clarity about their actual and permitted numbers.

Change-Id: I2c014e4633208cc7052fac265a995a8f2fe68151
Reviewed-on: https://go-review.googlesource.com/c/go/+/588355
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Dmitri Shuralyov 2024-05-24 17:56:31 -04:00 committed by Gopher Robot
parent a2eae66c30
commit 377646589d
2 changed files with 17 additions and 11 deletions
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20
src/text/template/exec_test.go
View file

@ -81,7 +81,8 @@ type T struct {
NilOKFunc func(*int) bool
ErrFunc func() (string, error)
PanicFunc func() string
InvalidReturnCountFunc func() (string, error, int)
TooFewReturnCountFunc func()
TooManyReturnCountFunc func() (string, error, int)
InvalidReturnTypeFunc func() (string, bool)
// Template to test evaluation of templates.
Tmpl *Template
@ -170,7 +171,8 @@ var tVal = &T{
NilOKFunc: func(s *int) bool { return s == nil },
ErrFunc: func() (string, error) { return "bla", nil },
PanicFunc: func() string { panic("test panic") },
InvalidReturnCountFunc: func() (string, error, int) { return "", nil, 0 },
TooFewReturnCountFunc: func() {},
TooManyReturnCountFunc: func() (string, error, int) { return "", nil, 0 },
InvalidReturnTypeFunc: func() (string, bool) { return "", false },
Tmpl: Must(New("x").Parse("test template")), // "x" is the value of .X
}
@ -1746,16 +1748,22 @@ func TestFunctionCheckDuringCall(t *testing.T) {
wantErr: "error calling call: wrong number of args for .VariadicFuncInt: got 0 want at least 1",
},
{
name: "call invalid return number func",
input: `{{call .InvalidReturnCountFunc}}`,
name: "call too few return number func",
input: `{{call .TooFewReturnCountFunc}}`,
data: tVal,
wantErr: "error calling call: too many return values for .InvalidReturnCountFunc",
wantErr: "error calling call: function .TooFewReturnCountFunc has 0 return values; should be 1 or 2",
},
{
name: "call too many return number func",
input: `{{call .TooManyReturnCountFunc}}`,
data: tVal,
wantErr: "error calling call: function .TooManyReturnCountFunc has 3 return values; should be 1 or 2",
},
{
name: "call invalid return type func",
input: `{{call .InvalidReturnTypeFunc}}`,
data: tVal,
wantErr: "error calling call: invalid function signature for .InvalidReturnTypeFunc: second argument should be error; is bool",
wantErr: "error calling call: invalid function signature for .InvalidReturnTypeFunc: second return value should be error; is bool",
},
{
name: "call pipeline",

8
src/text/template/funcs.go
View file

@ -110,18 +110,16 @@ func addFuncs(out, in FuncMap) {
// goodFunc reports whether the function or method has the right result signature.
func goodFunc(name string, typ reflect.Type) error {
numOut := typ.NumOut()
// We allow functions with 1 result or 2 results where the second is an error.
switch {
switch numOut := typ.NumOut(); {
case numOut == 1:
return nil
case numOut == 2 && typ.Out(1) == errorType:
return nil
case numOut == 2:
return fmt.Errorf("invalid function signature for %s: second argument should be error; is %s", name, typ.Out(1))
return fmt.Errorf("invalid function signature for %s: second return value should be error; is %s", name, typ.Out(1))
default:
return fmt.Errorf("too many return values for %s", name)
return fmt.Errorf("function %s has %d return values; should be 1 or 2", name, typ.NumOut())
}
}