go-configparser

Go implementation of the Python ConfigParser class.

This can parse Python-compatible ConfigParser config files, including support for option interpolation.

Setup

  import (
    "github.com/bigkevmcd/go-configparser"
  )

Parsing configuration files

It's easy to parse a configuration file.

  p, err := configparser.NewConfigParserFromFile("example.cfg")
  if err != nil {
    ...
  }

Methods

The ConfigParser implements most of the Python ConfigParser API

  v, err := p.Get("section", "option")
  err = p.Set("section", "newoption", "value")

  s := p.Sections()

Interpolation

The ConfigParser implements interpolation in the same format as the Python implementation.

Given the configuration

  [DEFAULTS]
  dir: testing

  [testing]
  something: %(dir)s/whatever

  v, err := p.GetInterpolated("testing, something")

It's also possible to override the values to use when interpolating values by providing a Dict to lookup values in.

  d := make(configparser.Dict)
  d["dir"] = "/a/non/existent/path"
  result, err := p.GetInterpolatedWithVars("testing", "something", d)

Will get testing/whatever as the value

Options

The ConfigParser supports almost all custom options available in the Python version.

• Delimiters - allows to set custom key-value pair delimiters.
• CommentPrefixes - allows to set custom comment line prefix. If line starts with one of the given Prefixes it will be passed during parsing.
• InlineCommentPrefixes - allows to set custom inline comment delimiter. This option checks if the line contains any of the given Prefixes and if so, splits the string by the prefix and returns the 0 index of the slice.
• MultilinePrefixes - allows to set custom multiline values prefixes. This option checks if the line starts with one of the given Prefixes and if so, counts it as a part of the current value.
• Strict - if set to true, parser will return new wrapped ErrAlreadyExist for duplicates of sections or options in one source.
• AllowEmptyLines - if set to true allows multiline values to include empty lines as their part. Otherwise the value will be parsed until an empty line or the line which does not start with one of the allowed multiline prefixes.
• Interpolation - allows to set custom behaviour for values interpolation. Interface was added, which defaults to chainmap.ChainMap instance.

type Interpolator interface {
	Add(...chainmap.Dict)
	Len() int
	Get(string) string
}

• Converters - allows to set custom values parsers.

type ConvertFunc func(string) (any, error)

ConvertFunc can modify requested value if needed e.g.,

package main

import (
	"fmt"
	"strings"

	"github.com/bigkevmcd/go-configparser"
)

func main() {
	stringConv := func(s string) (any, error) {
		return s + "_updated", nil
	}

	conv := configparser.Converter{
		configparser.String: stringConv,
	}

	p, err := configparser.ParseReaderWithOptions(
		strings.NewReader("[section]\noption=value\n\n"),
		configparser.Converters(conv),
	)
	// handle err

	v, err := p.Get("section", "option")
	// handle err

	fmt.Println(v == "value_updated") // true
}

Those functions triggered inside ConfigParser.Get* methods if presented and wraps the return value.

NOTE: Since ConvertFunc returns any, the caller should guarantee type assertion to the requested type after custom processing!

type Converter map[string]ConvertFunc

Converter is a map type, which supports int (for int64), string, bool, float (for float64) keys.

---

Default options, which are always preset:

func defaultOptions() *options {
	return &options{
		interpolation:     chainmap.New(),
		defaultSection:    defaultSectionName,
		delimiters:        ":=",
		commentPrefixes:   Prefixes{"#", ";"},
		multilinePrefixes: Prefixes{"\t", " "},
		converters: Converter{
			StringConv: defaultGet,
			IntConv:    defaultGetInt64,
			FloatConv:  defaultGetFloat64,
			BoolConv:   defaultGetBool,
		},
	}
}