Import path binding in source code

Abstract

Prov ide 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.