Configuration

Constago accepts YAML configuration through constago.yaml or the file passed to --config.

Complete shape

verbose: 1

input:
  dir: "."
  include: ["**/*.go"]
  exclude: ["**/*_test.go"]
  struct:
    explicit: false
    include_unexported: false
    only: ""
    except: ""
  field:
    explicit: false
    include_unexported: false
    only: ""
    except: ""

output:
  file_name: "constago.gen.go"
  initialisms: ["DB"]
  defaultInitialisms: true

elements:
  - name: "json"
    input:
      mode: "tagThenField"
      tag_priority: ["json"]
    output:
      mode: "constant"
      format:
        holder: "pascal"
        struct: "pascal"
        prefix: "json"
        suffix: ""
        initialisms: ["S3"]
        defaultInitialisms: true
      transform:
        tag_values: false
        value_case: "asIs"
        value_separator: ""
        initialisms: ["S3"]
        defaultInitialisms: true

getters:
  - name: "metadata"
    returns: ["json", ":value"]
    output:
      prefix: "metadata"
      suffix: ""
      format: "pascal"
      initialisms: ["S3"]
      defaultInitialisms: true

Root and input defaults

Key	Default
verbose	1
input.dir	.
input.include	["**/*.go"]
input.exclude	["**/*_test.go"]
input.struct.explicit	false
input.struct.include_unexported	false
input.struct.only	empty
input.struct.except	empty
input.field.explicit	false
input.field.include_unexported	false
input.field.only	empty
input.field.except	empty
output.file_name	constago.gen.go
output.initialisms	empty
output.defaultInitialisms	true

output.file_name must be a filename ending in .go; directory separators are rejected. Constago writes that filename into each selected package directory. Add the filename to input.exclude; it is not excluded automatically.

Initialism defaults and overrides

output.initialisms and output.defaultInitialisms establish the defaults for every element format, every element transform, and every getter output. Each of those entries can override either setting independently:

output:
  initialisms: ["DB"]
  defaultInitialisms: false

elements:
  - name: "json"
    output:
      format:
        # Replaces the inherited ["DB"] list for this format.
        initialisms: ["S3"]
      transform:
        # Keeps the inherited ["DB"] list but restores built-in initialisms.
        defaultInitialisms: true

When defaultInitialisms is true, the configured initialisms are added to Constago’s built-in Go initialisms. When it is false, only the configured list is recognized. Omitting a local property inherits its root output value; an explicit initialisms: [] replaces the inherited list with an empty one. Initialism rules affect only camel and pascal formats or transforms.

Element defaults

Defaults are applied independently to every entry in elements.

Key	Default
input.mode	tagThenField
input.tag_priority	["field", "json", "xml", "yaml", "toml", "sql"]
output.mode	constant
output.format.holder	pascal
output.format.struct	pascal
output.format.prefix	the element’s name
output.format.suffix	empty
output.format.initialisms	inherits output.initialisms
output.format.defaultInitialisms	inherits output.defaultInitialisms
output.transform.tag_values	false
output.transform.value_case	asIs
output.transform.value_separator	empty
output.transform.initialisms	inherits output.initialisms
output.transform.defaultInitialisms	inherits output.defaultInitialisms

Entries in tag_priority are literal struct tag names. The default field entry therefore reads a tag named field. Use input.mode: field to always derive values from Go field names, or tagThenField to fall back to them.

Getter defaults

Key	Default
output.prefix	the getter’s name
output.suffix	empty
output.format	pascal
output.initialisms	inherits root output.initialisms
output.defaultInitialisms	inherits root output.defaultInitialisms

Every getter needs at least one returns entry. Each entry must name a configured element or use the special :value token.

Valid values

• Input mode: tag, field, tagThenField
• Output mode: none, constant, struct
• Identifier format: camel, pascal, snake, snakeUpper
• Value case: asIs, camel, pascal, upper, lower
• Verbosity: 0, 1, 2

Element names, tag names, prefixes, suffixes, and configured initialisms must be valid Go identifiers. Include and exclude file patterns must end in .go, unless they use the package:NAME form.

Precedence

Explicit command-line flags override values loaded from YAML. Unchanged flag defaults do not overwrite YAML, which means --verbose 0 and boolean false overrides work as expected.