Last update March 7, 2012

DIP14

DIP14: Import path binding in source code

DIP:	14
Title:	Import path binding in source code
Version:	1
Status:	Draft
Created:	2011-10-18
Last Modified:	2011-10-18
Author:	Martin Nowak
Links:	Split of from DIP11

Abstract

Provide a language construct to declare import paths in source files.

Rationale

Declaring the location of dependencies should be done at the place where the dependency occurs. This reduces redundancy and maintenance effort. This is a requirement for DIP11.

Description

The specification for ImportDeclaration is extended as follows.

ModuleFullyQualifiedName:
        Identifier
        Expression of type String

Usage

module foo;
import "/path/bar.d";
import bar2="/path/bar2.d";
import "/path/bar3.d" : bar3fun;

void main()
{
  auto a = barfun();
  auto b = bar2fun();
  auto c = bar3fun();
}

This will not add a symbol bar to the current scope.

import "/path/bar.d"

An alternative would be to only allow alias imports.

Impact

Allowing an expression as module name does conflict with import bindings and alias imports.

@property string bar()
{
  return "/path/to/bar.d";
}
import bar;        // currently is an error due to name collision
static import bar; // ditto
import bar : fun;  // this would change it's behavior and evaluate bar
import baz = bar;  // ditto

Alternatives

It was proposed in DIP11 to add a new pragma(importpath, "ImportSpec") with the same rules as giving a command line import path.

This has two drawbacks. First one would need to statements to import a module.

pragma(importpath, "/path/to");
import bar;

Second using a pragma needs scoping rules. It was proposed that pragma(importpath) only be valid for that particular module. This has maintenance issues as every import from that path and the imported source themselves need to be kept in sync. One would need additional means to selectively transfer the import path to other modules.

Copyright

This document has been placed in the Public Domain.

Language Devel / DIPs / DIP14