package opam-format

  1. Overview
  2. Docs

Formulas on variables, as used in opam files build scripts

Filters are a small language of formulas over strings and booleans used for conditions and text replacements. It has relational operators over strings (using version-number comparison), And, Or and Not boolean operations, dynamic casting (using strings "true" and "false"), and string interpolation. Variables are resolved using a user function returning an option, undefined values are propagated.

String interpolation uses the syntax %{identifier}%

Identifiers have the form


The last optional part specifies a conversion from boolean to static strings.

The syntax pkg1+pkg2+pkgn:var is allowed as a shortcut to pkg1:var & pkg2:var & pkgn:var.

The special variable pkg:enable is allowed as a shortcut for pkg:installed?enable:disable

val to_string : OpamTypes.filter -> string


val fold_down_left : ('a -> OpamTypes.filter -> 'a) -> 'a -> OpamTypes.filter -> 'a

Folds on the tree of a filter

Maps on all nodes of a filter, bottom-up

Returns all the variables appearing in a filter (including the ones within string interpolations

Type of filter environment.

type fident = option list * OpamTypes.variable * (string * string) option

The type of filter idents with (optionally multiple) qualifying package names and optional string converter. Package name None encodes the self-reference _

Maps on all variables appearing in a filter. The case where package variables are renamed differently and appear in a filter ident of the form %{pkg1+pkg2:var}% is not supported and raises Invalid_argument.

val map_variables_in_string : (OpamTypes.full_variable -> OpamTypes.full_variable) -> string -> string

Same limitation as map_variables

val map_variables_in_fident : (OpamTypes.full_variable -> OpamTypes.full_variable) -> fident -> fident

Does not handle rewriting the variables to different names (which can't be expressed with a fident anymore), and raises Invalid_argument

val distribute_negations : ?neg:bool -> OpamTypes.filter -> OpamTypes.filter

Distributes the negations to apply only to atoms

val expand_string : ?partial:bool -> ?default:(string -> string) -> env -> string -> string

Rewrites string interpolations within a string. default is applied to the fident string (e.g. what's between %{ and }%) when the expansion is undefined. If unspecified, this raises Failure.

With partial, default defaults to the identity, and is otherwise expected to return a fident. In this case, the returned string is supposed to be expanded again (expansion results are escaped, escapes are otherwise kept). This makes the function idempotent

val unclosed_expansions : string -> ((int * int) * string) list

Returns the (beginning, end) offsets and substrings of any unclosed %{ expansions

Computes the value of a filter. May raise Failure if default isn't provided

val eval_to_bool : ?default:bool -> env -> OpamTypes.filter -> bool

Like eval but casts the result to a bool. Raises Invalid_argument if not a valid bool and no default supplied.

val opt_eval_to_bool : env -> OpamTypes.filter option -> bool

Same as eval_to_bool, but takes an option as filter and returns always true on None, false when the filter is Undefined. This is the most common behaviour for using "filters" for filtering

val eval_to_string : ?default:string -> env -> OpamTypes.filter -> string

Like eval but casts the result to a string

val partial_eval : env -> OpamTypes.filter -> OpamTypes.filter

Reduces what can be, keeps the rest unchanged

val ident_of_var : OpamTypes.full_variable -> fident

Wraps a full_variable into a fident accessor

val ident_of_string : string -> fident

A fident accessor directly referring a variable with the given name

Resolves a filter ident. Like eval, may raise Failure if no default is provided

val ident_string : ?default:string -> env -> fident -> string

Like ident_value, but casts the result to a string

val ident_bool : ?default:bool -> env -> fident -> bool

Like ident_value, but casts the result to a bool

val expand_interpolations_in_file : env -> OpamTypes.basename -> unit

Rewrites to basename, expanding interpolations. If the first line begins "opam-version:", assumes that expansion of variables within strings should be properly escaped. In particular, this means that Windows paths should expand correctly when generating .config files.

val commands : env -> OpamTypes.command list -> string list list

Processes filters evaluation in a command list: parameter expansion and conditional filtering

val single_command : env -> OpamTypes.arg list -> string list

Process a simpler command, without filters

val commands_variables : OpamTypes.command list -> OpamTypes.full_variable list

Extracts variables appearing in a list of commands

Converts a generic formula to a filter, given a converter for atoms

val filter_formula : ?default_version:OpamTypes.version -> ?default:bool -> env -> OpamTypes.filtered_formula -> OpamTypes.formula

Resolves the filter in a filtered formula, reducing to a pure formula.

default is the assumed result for undefined filters. If a version filter doesn't resolve to a valid version, the constraint is dropped unless default_version is specified.

May raise, as other filter functions, if default is not provided and filters don't resolve.

val partial_filter_formula : env -> OpamTypes.filtered_formula -> OpamTypes.filtered_formula

Reduces according to what is defined in env, and returns the simplified formula

val gen_filter_formula : ('a -> [< `True | `False | `Formula of 'b OpamTypes.generic_formula ]) -> ('c * 'a) OpamFormula.formula -> ('c * 'b OpamTypes.generic_formula) OpamFormula.formula

A more generic formula reduction function, that takes a "partial resolver" as argument

val string_of_filtered_formula : OpamTypes.filtered_formula -> string
val variables_of_filtered_formula : OpamTypes.filtered_formula -> OpamTypes.full_variable list
val filter_deps : build:bool -> post:bool -> ?test:bool -> ?doc:bool -> ?dev:bool -> ?default_version:OpamTypes.version -> ?default:bool -> OpamTypes.filtered_formula -> OpamTypes.formula

Resolves the build, post, test, doc, dev flags in a filtered formula (which is supposed to have been pre-processed to remove switch and global variables). default determines the behaviour on undefined filters, and the function may raise if it is undefined. If a constraint resolves to an invalid version, it is dropped, or replaced with default_version if specified. If test, doc or dev are unspecified, they are assumed to be filtered out already and encountering them will raise an assert.

val deps_var_env : build:bool -> post:bool -> ?test:bool -> ?doc:bool -> ?dev:bool -> env

The environment used in resolving the dependency filters, as per filter_deps.

Like OpamFormula.simplify_version_formula, but on filtered formulas (filters are kept unchanged, but put in front)


Innovation. Community. Security.