importing: Import a module or package

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Import a module or package

Description

Actual implementation of the import process

Usage

use_one(declaration, alias, caller, use_call)

load_and_register(spec, info, caller)

register_as_import(spec, info, mod_ns, caller)

defer_import_finalization(spec, info, mod_ns, caller)

finalize_deferred(info)

export_and_attach(spec, info, mod_ns, caller)

load_from_source(info, mod_ns)

load_mod(info)

mod_exports(info, spec, mod_ns)

mod_export_names(info, mod_ns)

attach_to_caller(spec, info, mod_exports, mod_ns, caller)

attach_list(spec, exports)

assign_alias(spec, mod_exports, caller)

assign_temp_alias(spec, caller)

Arguments

declaration	an unevaluated use declaration expression without the surrounding use call
alias	the use alias, if given, otherwise NULL
caller	the client’s calling environment (parent frame)
use_call	the use call which is invoking this code
spec	a module use declaration specification
info	the physical module information
mod_ns	the module namespace environment of the newly loaded module

Details

use_one performs the actual import. It is invoked by use given the calling context and unevaluated expressions as arguments, and only uses standard evaluation.

load_and_register performs the loading, attaching and exporting of a module identified by its spec and info.

register_as_import registers a use declaration in the calling module so that it can be found later on, if the declaration is reexported by the calling module.

defer_import_finalization is called by load_and_register to earmark a module for deferred initialization if it hasn’t been fully loaded yet.

finalize_deferred exports and attaches names from a module use declaration which has been deferred due to being part of a cyclic loading chain.

export_and_attach exports and attaches names from a given module use declaration.

load_from_source loads a module source file into its newly created, empty module namespace.

load_mod tests whether a module or package was already loaded and, if not, loads it.

mod_exports returns an export environment containing a copy of the module’s exported objects.

attach_to_caller attaches the listed names of an attach specification for a given use declaration to the calling environment.

assign_alias creates a module/package object in calling environment, unless it contains an attach declaration, and no explicit alias is given.

assign_temp_alias creates a placeholder object for the module in the calling environment, to be replaced by the actual module export environment once the module is completely loaded (which happens in the case of cyclic imports).

Value

use_one does not currently return a value. — This might change in the future.

load_mod returns the module or package namespace environment of the specified module or package info.

mod_exports returns an export environment containing the exported names of a given module.

mode_export_names returns a vector containing the same names as names(mod_exports(info, spec, mod_ns)) but does not create an export environment.

attach_list returns a named character vector of the names in an attach specification. The vector’s names are the aliases, if provided, or the attach specification names themselves otherwise.

Note

If a module is still being loaded (because it is part of a cyclic import chain), load_and_register earmarks the module for deferred registration and holds off on attaching and exporting for now, since not all its names are available yet.

box documentation built on May 29, 2024, 5:55 a.m.