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There is no LICENSE.md file, but there is a LICENSE file.
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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.
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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The reporter tries to aggresively elide data that is not interesting
to the user. However, doing so many result in an output that does not
visually indicate the difference between semantically different objects.
This CL modifies the reporter to try increasingly verbose presets until
two different objects are formatted differently.
This CL includes a custom implementation of reflect.Type.String that
can print the type with fully qualified names to disambiguate types
that happen to have the same base package name.
Fixes #194
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For large slices, arrays, and maps, the reporter can be unreadable
if there are many differences. Limit the number of results to some
reasonable maximum.
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Using strings.Join to denote differences in a multi-line string is
visually noisy due to extensive use of quotes and escape sequences.
Add a custom triple-quote syntax that unambiguously shows line
differences with less visual noise.
If the triple-quote syntax cannot unmabiguously show differences,
then the reporter falls back on using the strings.Join format,
which is never ambiguous.
Fixes #195
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Rather than having a single element on each line,
which hurts readability due to the need for scrolling quite a bit.
Batch multiple elements for simple lists to be on a single line.
Fixes #170
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- No need to wrap ToUpper & Fields
- Simpler concatenation
- Easier pointer access
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The previous implementation of the reporter simply listed all differences,
each qualified by the full path to the difference.
This method of reporting is exact, but difficult for humans to parse.
It is one of the more common sources of complaints by users and a significant
reason why cmp is not preferred over competing libraries.
This change reimplements the reporter to format the output as a
structured literal in pseudo-Go syntax. The output resembles literals that
the user would likely have in their test code. Differences between the
x and y values are denoted by a '-' or '+' prefix at the start of the line.
An overview of the new implementation is as follows:
* report.go: The defaultReporter type implements the Reporter interface.
* report_value: Through the PushStep/PopStep API, the defaultReporter is able
to contruct an in-memory valueNode tree representing the comparison of
x and y as cmp.Equal walks the sub-values.
* report_compare.go: After report_value.go constructs an AST-representation
of the compared values, report_compare.go formats the valueNode tree as a
textNode tree, which is the textual output in a tree form.
Some relevant design decisions include:
* The format logic goes through effort to avoid printing ignored nodes.
* Some number of surrounding equal (but not ignored) struct fields,
slice elements, or map entries are printed for context.
* cmp.Equal may declare two sub-reflect.Values to be equal, but are
different values when printed. In order to present a unified view on
this "equal" node, the logic formats both values and arbitrarily choses
the one with the shorter string.
* Transformed nodes are formatted with the pseudo-Go syntax of:
Inverse(TransformerName, OutputType{...})
where Inverse is some magical pseudo-function that inverts the
transformation referred to by TransformerName. The OutputType literal
is the output of the transformation.
* report_reflect.go: This contains logic to pretty-print reflect.Values and
is relied upon by report_compare.go to format the leaves of the tree.
Note that the leaves of the tree can be any arbitrary Go type and value
(including cyclic data structures).
* report_text.go: This contains logic for purely lexicographical formatting
and is depended upon by the other report_*.go files.
Advantages:
* The output is more familiar as it uses pseudo-Go syntax for literals
* It provides context about surrounding struct fields, slice elements, or
map entries that were equal
* Inserted and removed elements in a slice are easier to visualize
* Related diffs lie on the same indentation
* For diffs in a deeply nested value, the output is easier to visualize
than having a list of all the full paths to the diff.
Disadvantages:
* The implementation is drastically more complex.
* In most cases, the output is longer (though more sparse)
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