117 lines
3.6 KiB
Markdown
117 lines
3.6 KiB
Markdown
go-spew
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=======
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Go-spew implements a deep pretty printer for Go data structures to aid in
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debugging. A comprehensive suite of tests with 100% test coverage is provided
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to ensure proper functionality. See `test_coverage.txt` for the gocov coverage
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report. Go-spew is licensed under the liberal ISC license, so it may be used in
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open source or commercial projects.
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If you're interested in reading about how this package came to life and some
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of the challenges involved in providing a deep pretty printer, there is a blog
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post about it
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[here](https://blog.cyphertite.com/go-spew-a-journey-into-dumping-go-data-structures/).
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## Documentation
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Full `go doc` style documentation for the project can be viewed online without
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installing this package by using the excellent GoDoc site here:
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http://godoc.org/github.com/davecgh/go-spew/spew
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You can also view the documentation locally once the package is installed with
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the `godoc` tool by running `godoc -http=":6060"` and pointing your browser to
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http://localhost:6060/pkg/github.com/davecgh/go-spew/spew
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## Installation
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```bash
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$ go get github.com/davecgh/go-spew/spew
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```
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## Quick Start
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To dump a variable with full newlines, indentation, type, and pointer
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information use Dump or Fdump:
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```Go
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spew.Dump(myVar1, myVar2, ...)
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spew.Fdump(someWriter, myVar1, myVar2, ...)
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```
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Alternatively, if you would prefer to use format strings with a compacted inline
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printing style, use the convenience wrappers Printf, Fprintf, etc with %v (most
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compact), %+v (adds pointer addresses), %#v (adds types), or %#+v (adds types
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and pointer addresses):
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```Go
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spew.Printf("myVar1: %v -- myVar2: %+v", myVar1, myVar2)
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spew.Printf("myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
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spew.Fprintf(someWriter, "myVar1: %v -- myVar2: %+v", myVar1, myVar2)
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spew.Fprintf(someWriter, "myVar3: %#v -- myVar4: %#+v", myVar3, myVar4)
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```
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## Sample Dump Output
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```
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(main.Foo) {
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unexportedField: (*main.Bar)(0xf84002e210)({
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flag: (main.Flag) flagTwo,
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data: (uintptr) <nil>
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}),
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ExportedField: (map[interface {}]interface {}) {
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(string) "one": (bool) true
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}
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}
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```
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## Sample Formatter Output
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Double pointer to a uint8:
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```
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%v: <**>5
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%+v: <**>(0xf8400420d0->0xf8400420c8)5
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%#v: (**uint8)5
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%#+v: (**uint8)(0xf8400420d0->0xf8400420c8)5
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```
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Pointer to circular struct with a uint8 field and a pointer to itself:
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```
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%v: <*>{1 <*><shown>}
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%+v: <*>(0xf84003e260){ui8:1 c:<*>(0xf84003e260)<shown>}
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%#v: (*main.circular){ui8:(uint8)1 c:(*main.circular)<shown>}
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%#+v: (*main.circular)(0xf84003e260){ui8:(uint8)1 c:(*main.circular)(0xf84003e260)<shown>}
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```
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## Configuration Options
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Configuration of spew is handled by fields in the ConfigState type. For
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convenience, all of the top-level functions use a global state available via the
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spew.Config global.
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It is also possible to create a ConfigState instance that provides methods
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equivalent to the top-level functions. This allows concurrent configuration
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options. See the ConfigState documentation for more details.
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```
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* Indent
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String to use for each indentation level for Dump functions.
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It is a single space by default. A popular alternative is "\t".
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* MaxDepth
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Maximum number of levels to descend into nested data structures.
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There is no limit by default.
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* DisableMethods
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Disables invocation of error and Stringer interface methods.
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Method invocation is enabled by default.
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* DisablePointerMethods
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Disables invocation of error and Stringer interface methods on types
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which only accept pointer receivers from non-pointer variables.
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Pointer method invocation is enabled by default.
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```
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## License
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Go-spew is licensed under the liberal ISC License.
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