https://github.com/galdor/go-pp
A flexible Golang pretty printer.
https://github.com/galdor/go-pp
debugging golang pretty-printer
Last synced: 6 months ago
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A flexible Golang pretty printer.
- Host: GitHub
- URL: https://github.com/galdor/go-pp
- Owner: galdor
- License: isc
- Created: 2024-11-02T16:09:34.000Z (11 months ago)
- Default Branch: master
- Last Pushed: 2024-11-11T13:49:17.000Z (11 months ago)
- Last Synced: 2024-11-24T04:58:45.171Z (11 months ago)
- Topics: debugging, golang, pretty-printer
- Language: Go
- Homepage:
- Size: 371 KB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# go-pp
## Introduction
The go-pp library —"pp" being for "pretty printer"— contains utilities to pretty
print Go values. Its main use case is to help debugging. The `%#v` standard
formatting sequence is fundamentally user hostile: no indentation, prints
pointers instead of recursing, expands values that should not be expanded (e.g.
`time.Time` values).
The printing algorithm tries its best to present values in a useful way. Types
are printed when it makes sense, simple values are displayed inline when
possible, various standard types have a custom representation.
Example:
```go
info, _ := os.Stat("/dev/stdout")
p.Print(info, "standard output")
```
Debugging is hard. The `pp` package makes it easier.
## Usage
### Printing values
Import `go.n16f.net/pp` and call `pp.Print` with any value as argument. Extra
arguments are used as a format string and arguments to add a label to the
output.
For example:
```go
pp.Print(os.Getenv("HOME"), "home directory")
```
```
[command line arguments] []string(["./test"])
```
### Configuring printers
Printers can be configured with various settings to match your preferences. The
following options are available:
- `(*Printer).SetDefaultOutput`: set the output (`io.Writer`) used by the
printer for the `Print` method (default: `os.Stdout`).
- `(*Printer).SetFormatValueFunc`: set the function used to override value
formatting. See the section about custom formatting below for more
information (default: `pp.FormatValue`)
- `(*Printer).SetMaxInlineColumn`: set the column beyond which the printer will
revert to the normal output format when trying to print a value inline
(default: 80).
- `(*Printer).SetIndent`: set the string used for each indentation level
(default: `" "`).
- `(*Printer).SetLinePrefix`: set a string to be printed at the beginning of
each output line.
- `(*Printer).SetPrintTypes`: control type printing. Can be either:
- `pp.PrintTypesDefault`: print the type of values when it is not obvious;
- `pp.PrintTypesAlways`: print the type of all values;
- `pp.PrintTypesNever`: never print any type.
- `(*Printer).SetHidePrivateFields`: hide private (non-exported) fields when
printing structures.
- `(*Printer).SetThousandsGroupingMinDigits`: the minimum number of digits for a
number to be printed with thousand separators (default: 6).
- `(*Printer).SetThousandsSeparator`: set the character (rune) used between
groups of three digits when printing numbers (default: `'_'`).
You can either modify the default printer used by `pp.Print`
(`pp.DefaultPrinter`) or create your own printer.
See the [`custom-printer` program](examples/custom-printer/main.go) for an
example.
Printers are thread safe.
### Custom formatting
It is possible to control the representation of specific types. Use
`(*Printer).SetFormatValueFunc` to pass your own function.
The function accept a `reflect.Value` argument and can return an `any` value
which can be either:
- `nil` to use the default printer representation;
- a value of type `RawString` to print the value as a string without any further
formatting (e.g. `RawString("foo")` will simply print `foo`);
- any other value to be formatted by the printer.
Printers will only call this function on values, not pointers.
The default function, `pp.FormatValue` handles various standard types such as
`time.Time` or `regexp.Regexp`.
See the [`custom-formatting` program](examples/custom-formatting/main.go) for an
example.
### Documentation
Refer to the [Go package documentation](https://pkg.go.dev/go.n16f.net/pp)
for information about the API.
# Licensing
Go-pp is open source software distributed under the
[ISC](https://opensource.org/licenses/ISC) license.