Fix keyword internalization in defsystem and defpackage

[kilianmh]

Replaced all keyword arguments with uninterned symbols in DEFPACKAGE and IN-PACKAGE. This should reduce pollution of namespace and enable consistent highlighting in editors.

[gefjon]

Personally, I am of the opinion that package names should be written as keywords, because I value having them autocompleted.

For symbol names in clauses like :export, I certainly favor using uninterned symbols, and will gladly merge those changes.

I find it both aesthetically pleasing and useful that, when a package definition lists package names as keywords and symbol names as uninterned symbols, my editor highlights them differently; it makes skimming the package definitions much easier.

I'd like input from some other people, ideally, as to whether it's preferable to write defpackage :cl-ppcre or defpackage #:cl-ppcre.

[phoe]

Two cents from me: I don't care much for package autocompletion since my interactive package traversal happens mostly via the slime REPL shortcut ,in and via C-c ~; as for programmatic use, I write in-package forms seldom enough to not really think about autocompletion for them. I'd personally use gensyms, but I have no strong opinion against keywords in the case you mentioned.

[hanshuebner]

Why is "polluting the namespace" a problem?

[phoe]

I guess it's about a) keeping keyword syntax completions minimal and b) microoptimizations, since you can't portably unintern a keyword without UB.

[gefjon]

Why is "polluting the namespace" a problem?

Editors (i.e. Emacs with SLIME or SLY) examine the accessible symbols in a package when autocompleting. With no package prefix, they search the interned symbols in *package*; with a single-colon package prefix, they search the external symbols of that package. This is exactly what you want for every package except keyword, where all symbols are automatically exported. When you begin typing a keyword and trigger autocomplete, the editor searches through every keyword that's ever been interned. This set is often quite large, and contains many bad suggestions; this means that a user must type more characters before autocomplete on keywords finds the intended symbol. This problem can be partially negated by avoiding interning keywords that you'll never use again. No one will ever use any of the keywords in the :export clause of the defpackage :cl-ppcre form, so they should instead be uninterned symbols.

I write in-package forms seldom enough to not really think about autocompletion for them

I favor a package-per-file style with ASDF's package-inferred-system, so I find myself writing defpackage or uiop:define-package forms relatively frequently, and listing relatively many packages in :use or:import-from clauses. For a package name as short as cl-ppcre it doesn't matter much, but in general I like having autocomplete so I can type e.g. :tri-ba M-i rather than all of :trivial-backtrace.

[hanshuebner]

No one will ever use any of the keywords in the :export clause of the defpackage :cl-ppcre form, so they should instead be uninterned symbols.

Thank you for explaining, that is a good reason.

[kilianmh]

Thank you for the valuable feedback! According to this post from Rainer Joswig, another problem might be:

The usual expectation is that unreferenced symbols interned in packages might not be removed by a Garbage Collector (GC) - the Common Lisp standard says nothing about this topic and has no required behavior. So adding new symbols to a package often keeps it growing. This could be a memory leak in some applications.

Now in-package arguments and defpackage name, :nicknames, :use clauses are reverted back to keywords. The pull request now comprises uninterened symbols in the defpackage clauses :shadow :shadowing-import-from :import-from :export.

[kilianmh]

Reverted :SHADOWING-IMPORT-FROM and :IMPORT-FROM package names to KEYWORD, which should improve readability without unnecessary expansion of *PACKAGE*.

[kilianmh]

Summary:

Fix keyword internalization in defsystem and defpackage

• Replace keywords in defpackage and defsystem (Remaining: library names)
• Simplify :perform clause in defsystem

-> 35 less keywords interned when loading cl-ppcre
-> 37 less keywords interned when loading cl-ppcre-unicode