Improve reporting of values with cycles #217
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This is the last major cmp change I have in mind. It's unfortunately a bit complex as cycle detection is hard. Printing cycles in a sensible way for humans is even harder. |
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cybrcodr
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Jun 17, 2020
cmp/report_reflect.go
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| return &textWrap{Prefix: typeName, Value: wrapParens(s)} | ||
| } | ||
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| // wrapParens wraps s with a set of parenthesis, but avoids it if it is super |
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Thank you for reviewing all my changes. I think this concludes my series of planned cmp improvements. |
Previously, the reporter could handle formatting values with cycles
in that it did not crash with a stack overflow. However, the output
was not particularly understandable as it did not surface to the user
why a particular value was truncated, and if it was truncated due
to a cyclic reference, what was the referent.
This change annotates the reporter tree with pointer information
so that a later pass can inject reference information if it is needed
to produce more understandable output.
Consider the following example:
map[string]*cmp_test.CycleAlpha{
"Foo": &⟪ref#0⟫{
Name: "Foo",
Bravos: map[string]*cmp_test.CycleBravo{
"FooBravo": &{
- ID: 101,
+ ID: 0,
Name: "FooBravo",
Mods: 100,
Alphas: {"Foo": &⟪ref#0⟫(...)},
},
},
},
}
This graph contains a cycle. To ensure that a graph can be formatted,
the cycle is truncated as indicated with: &⟪ref#0⟫(...).
The referent was identified earlier with: &⟪ref#0⟫{...}.
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Previously, the reporter could handle formatting values with cycles
in that it did not crash with a stack overflow. However, the output
was not particularly understandable as it did not surface to the user
why a particular value was truncated, and if it was truncated due
to a cyclic reference, what was the referent.
This change annotates the reporter tree with pointer information
so that a later pass can inject reference information if it is needed
to produce more understandable output.