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Catch panic when using go-spew #1824

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Catch panic when using go-spew #1824

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36 changes: 25 additions & 11 deletions assert/assertions.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1948,19 +1948,28 @@ func diff(expected interface{}, actual interface{}) string {

var e, a string

switch et {
case reflect.TypeOf(""):
e = reflect.ValueOf(expected).String()
a = reflect.ValueOf(actual).String()
case reflect.TypeOf(time.Time{}):
e = spewConfigStringerEnabled.Sdump(expected)
a = spewConfigStringerEnabled.Sdump(actual)
default:
e = spewConfig.Sdump(expected)
a = spewConfig.Sdump(actual)
// Use spew to create string representations of the objects
// We have to guard against panics in spew.
// See https://github.com/stretchr/testify/issues/480
panicked, _, _ := didPanic(func() {
switch et {
case reflect.TypeOf(""):
e = reflect.ValueOf(expected).String()
a = reflect.ValueOf(actual).String()
case reflect.TypeOf(time.Time{}):
e = spewConfigStringerEnabled.Sdump(expected)
a = spewConfigStringerEnabled.Sdump(actual)
default:
e = spewConfig.Sdump(expected)
a = spewConfig.Sdump(actual)
}
})
if panicked {
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@brackendawson brackendawson Nov 17, 2025

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Panics are not exceptions, we should not be blindly ignoring them. If there is a case we know of that spew can't handle then we should avoid it or fix spew, potentially by vendoring it.

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@ccoVeille ccoVeille Nov 17, 2025

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It's what I suggested in the PR that was created earlier

@brackendawson do you remember the discussion we had about importing the code of go-spew, the same way we imported difflib ?

The conclusion was not yet, because we don't know yet the "unforseen consequences" of importing the code of go-difflib, so we don't have enough information and experience on this.

Maybe it's time to reconsider it.

Importing the code of go-spew diff and and fixing the bug in the code could be considered.

Originally posted by @ccoVeille in #1816 (comment)

I'm glad we converge here.

It would also help to remove the imperfect hack about time.Time by patching it to use the stringer even when DisableMethods is true.

// silently ignore diff if we panic during spew, the library is no longer maintained
return ""
}

diff, _ := difflib.GetUnifiedDiffString(difflib.UnifiedDiff{
diff, err := difflib.GetUnifiedDiffString(difflib.UnifiedDiff{
A: difflib.SplitLines(e),
B: difflib.SplitLines(a),
FromFile: "Expected",
Expand All @@ -1970,6 +1979,11 @@ func diff(expected interface{}, actual interface{}) string {
Context: 1,
})

if err != nil {
// silently ignore diff if the external library fails to compute it
return ""
}

return "\n\nDiff:\n" + diff
}

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33 changes: 33 additions & 0 deletions assert/assertions_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -837,6 +837,39 @@ func TestEqualFormatting(t *testing.T) {
}
}

func TestEqualFormattingWithPanic(t *testing.T) {
t.Parallel()

type structWithUnexportedMapWithArrayKey struct {
m interface{}
}

for _, c := range []struct {
a interface{}
b interface{}
}{
{
// from the issue https://github.com/stretchr/testify/pull/1816
a: structWithUnexportedMapWithArrayKey{
map[[1]byte]*struct{}{
{1}: nil,
{2}: nil,
},
},
b: structWithUnexportedMapWithArrayKey{},
},
} {

mockT := new(mockTestingT)
NotPanics(t, func() {
Equal(mockT, c.a, c.b)
}, "should not panic")

True(t, mockT.Failed(), "should have failed")
Contains(t, mockT.errorString(), "Not equal:", "error message should mention inequality")
}
}

func TestFormatUnequalValues(t *testing.T) {
t.Parallel()

Expand Down