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Published: Nov 17, 2020 License: Apache-2.0 Imports: 25 Imported by: 4




Library providing routines to merge and validate JSON, YAML, TOML files and/or structs (godoc)

Typical use case: Make your application configuration files multi-format, modular, templated, sparse, location-independent and validated

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Conflate is a library and cli-tool, that provides the following features :

  • merge data from multiple formats (JSON/YAML/TOML/go structs) and multiple locations (filesystem paths and urls)
  • validate the merged data against a JSON schema
  • apply any default values defined in a JSON schema to the merged data
  • expand environment variables inside the data
  • marshal merged data to multiple formats (JSON/YAML/TOML/go structs)

It supports draft-04, draft-06 and draft-07 of JSON Schema. If the key $schema is missing, or the draft version is not explicitly set, a hybrid mode is used which merges together functionality of all drafts into one mode. Improvements, ideas and bug fixes are welcomed.

Getting started

Run the following command, which will build and install the latest binary in $GOPATH/bin

go get

Alternatively, you can install one of the pre-built release binaries from

Usage of Library

Please refer to the godoc and the example code

Usage of CLI Tool

Help can be obtained in the usual way :

$conflate --help
Usage of conflate:
  -data value
    	The path/url of JSON/YAML/TOML data, or 'stdin' to read from standard input
    	Apply defaults from schema to data
    	Expand environment variables in files
  -format string
    	Output format of the data JSON/YAML/TOML
  -includes string
    	Name of includes array. Blank string suppresses expansion of includes arrays (default "includes")
    	Switches off conflation of includes. Overrides any --includes setting.
  -schema string
    	The path/url of a JSON v4 schema file
    	Validate the data against the schema
    	Display the version number

To conflate the following file ... :

$cat ./testdata/valid_parent.json
  "includes": [
  "parent_only" : "parent",
  "parent_child" : "parent",
  "parent_sibling" : "parent",
  "all": "parent"
} the following command, which will merge valid_parent.json, valid_child.json, valid_sibling.json :

$conflate -data ./testdata/valid_parent.json -format JSON
  "all": "parent",
  "child_only": "child",
  "parent_child": "parent",
  "parent_only": "parent",
  "parent_sibling": "parent",
  "sibling_child": "sibling",
  "sibling_only": "sibling"

Note how the includes are loaded remotely as relative paths.

Also, note values in a file override values in any included files, and that an included file overrides values in any included file above it in the includes list.

If you instead host a file somewhere else, then just use a URL :

$conflate -data -format JSON
  "all": "parent",
  "child_only": "child",
  "parent_child": "parent",
  "parent_only": "parent",
  "parent_sibling": "parent",
  "sibling_child": "sibling",
  "sibling_only": "sibling"

The includes here are also loaded as relative urls and follow exactly the same merging rules.

To output in a different format use the -format option, e.g. TOML :

$conflate -data ./testdata/valid_parent.json -format TOML
all = "parent"
child_only = "child"
parent_child = "parent"
parent_only = "parent"
parent_sibling = "parent"
sibling_child = "sibling"
sibling_only = "sibling"

To additionally use defaults from a JSON schema and validate the conflated data against the schema, use -defaults and -validate respectively :

$cat ./testdata/blank.yaml

$conflate -data ./testdata/blank.yaml -schema ./testdata/test.schema.json -validate -format YAML
Schema validation failed : The document is not valid against the schema : Invalid type. Expected: object, given: null (#)

$conflate -data ./testdata/blank.yaml -schema ./testdata/test.schema.json -defaults -validate -format YAML
all: parent
child_only: child
parent_child: parent
parent_only: parent
parent_sibling: parent
sibling_child: sibling
sibling_only: sibling

Note any defaults are applied before validation is performed, as you would expect.

If you don't want to intrusively embed an "includes" array inside your JSON, you can instead provide multiple data files which are processed from left-to-right :

$conflate -data ./testdata/valid_child.json -data ./testdata/valid_sibling.json -format JSON
  "all": "sibling",
  "child_only": "child",
  "parent_child": "child",
  "parent_sibling": "sibling",
  "sibling_child": "sibling",
  "sibling_only": "sibling"

Or alternatively, you can create a top-level JSON file containing only the includes array. For fun, lets choose to use YAML for the top-level file, and output TOML :

$cat toplevel.yaml
  - testdata/valid_child.json
  - testdata/valid_sibling.json

$conflate -data toplevel.yaml -format TOML
all = "sibling"
child_only = "child"
parent_child = "child"
parent_sibling = "sibling"
sibling_child = "sibling"
sibling_only = "sibling"

If you want to read a file from stdin you can do the following. Here we pipe in some TOML to override a value to demonstrate :

$echo 'all="MY OVERRIDDEN VALUE"' |  conflate -data ./testdata/valid_parent.json -data stdin  -format JSON
  "child_only": "child",
  "parent_child": "parent",
  "parent_only": "parent",
  "parent_sibling": "parent",
  "sibling_child": "sibling",
  "sibling_only": "sibling"

Note that in all cases -data sources are processed from left-to-right, with values in right files overriding values in left files, so the following doesn't work :

$echo 'all="MY OVERRIDDEN VALUE"' |  conflate -data stdin -data ./testdata/valid_parent.json  -format JSON
  "all": "parent",
  "child_only": "child",
  "parent_child": "parent",
  "parent_only": "parent",
  "parent_sibling": "parent",
  "sibling_child": "sibling",
  "sibling_only": "sibling"

You can optionally expand environment variables in the files like this :

$export echo MYVALUE="some value"
$export echo MYJSONMAP='{ "item1" : "value1" }'
$echo '{ "my_value": "$MYVALUE", "my_map": $MYJSONMAP }' | conflate -data stdin -expand -format JSON
  "my_map": {
    "item1": "value1"
  "my_value": "some value"


Images derived from originals by Renee French



Package conflate is a library that helps to merge and validate data from multiple formats (JSON/YAML/TOML), and multiple locations (filesystem paths and urls).



This section is empty.


View Source
var Includes = "includes"

Includes is used to specify the top level key that holds the includes array

View Source
var Unmarshallers = UnmarshallerMap{
	".json": {JSONUnmarshal},
	".jsn":  {JSONUnmarshal},
	".yaml": {YAMLUnmarshal},
	".yml":  {YAMLUnmarshal},
	".toml": {TOMLUnmarshal},
	".tml":  {TOMLUnmarshal},
	"":      {JSONUnmarshal, YAMLUnmarshal, TOMLUnmarshal},

Unmarshallers is a list of unmarshalling functions to be used for given file extensions. The unmarshaller slice for the blank file extension is used when no match is found.


func JSONUnmarshal

func JSONUnmarshal(data []byte, out interface{}) error

JSONUnmarshal unmarshals the data as JSON

func TOMLUnmarshal

func TOMLUnmarshal(data []byte, out interface{}) error

TOMLUnmarshal unmarshals the data as TOML

func YAMLUnmarshal

func YAMLUnmarshal(data []byte, out interface{}) error

YAMLUnmarshal unmarshals the data as YAML


type Conflate

type Conflate struct {
	// contains filtered or unexported fields

Conflate contains a 'working' merged data set and optionally a JSON v4 schema

func FromData

func FromData(data ...[]byte) (*Conflate, error)

FromData constructs a new Conflate instance populated with the given data

func FromFiles

func FromFiles(paths ...string) (*Conflate, error)

FromFiles constructs a new Conflate instance populated with the data from the given files

func FromGo

func FromGo(data ...interface{}) (*Conflate, error)

FromGo constructs a new Conflate instance populated with the given golang objects

func FromURLs

func FromURLs(urls ...url.URL) (*Conflate, error)

FromURLs constructs a new Conflate instance populated with the data from the given URLs

func New

func New() *Conflate

New constructs a new empty Conflate instance

func (*Conflate) AddData

func (c *Conflate) AddData(data ...[]byte) error

AddData recursively merges the given data into the Conflate instance

func (*Conflate) AddFiles

func (c *Conflate) AddFiles(paths ...string) error

AddFiles recursively merges the data from the given files into the Conflate instance

func (*Conflate) AddGo

func (c *Conflate) AddGo(objs ...interface{}) error

AddGo recursively merges the given (json-serializable) golang objects into the Conflate instance

func (*Conflate) AddURLs

func (c *Conflate) AddURLs(urls ...url.URL) error

AddURLs recursively merges the data from the given urls into the Conflate instance

func (*Conflate) ApplyDefaults

func (c *Conflate) ApplyDefaults(s *Schema) error

ApplyDefaults sets any nil or missing values in the data, to the default values defined in the JSON v4 schema

func (*Conflate) Expand

func (c *Conflate) Expand(expand bool)

Expand is an option to automatically expand environment variables in data files

func (*Conflate) MarshalJSON

func (c *Conflate) MarshalJSON() ([]byte, error)

MarshalJSON exports the data as JSON

func (*Conflate) MarshalTOML

func (c *Conflate) MarshalTOML() ([]byte, error)

MarshalTOML exports the data as TOML

func (*Conflate) MarshalYAML

func (c *Conflate) MarshalYAML() ([]byte, error)

MarshalYAML exports the data as YAML

func (*Conflate) Unmarshal

func (c *Conflate) Unmarshal(out interface{}) error

Unmarshal extracts the data as a Golang object

func (*Conflate) Validate

func (c *Conflate) Validate(s *Schema) error

Validate checks the data against the JSON v4 schema

type Schema

type Schema struct {
	// contains filtered or unexported fields

Schema contains a JSON v4 schema

func NewSchemaData

func NewSchemaData(data []byte) (*Schema, error)

NewSchemaData loads a JSON v4 schema from the given data

func NewSchemaFile

func NewSchemaFile(path string) (*Schema, error)

NewSchemaFile loads a JSON v4 schema from the given path

func NewSchemaGo

func NewSchemaGo(s interface{}) (*Schema, error)

NewSchemaGo creates a Schema instance from a schema represented as a golang object

func NewSchemaURL

func NewSchemaURL(url url.URL) (*Schema, error)

NewSchemaURL loads a JSON v4 schema from the given URL

func (*Schema) ApplyDefaults

func (s *Schema) ApplyDefaults(pData interface{}) error

ApplyDefaults adds default values defined in the schema to the data pointed to by pData

func (*Schema) Validate

func (s *Schema) Validate(data interface{}) error

Validate checks the given golang data against the schema

type UnmarshallerFunc

type UnmarshallerFunc func([]byte, interface{}) error

UnmarshallerFunc defines the type of function used for unmarshalling data

type UnmarshallerFuncs

type UnmarshallerFuncs []UnmarshallerFunc

UnmarshallerFuncs defines the type for a slice of UnmarshallerFunc

type UnmarshallerMap

type UnmarshallerMap map[string]UnmarshallerFuncs

UnmarshallerMap defines the type of a map of string to UnmarshallerFuncs


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