common-lisp - 使用 ASDF 加载可选组件

Question

如何告诉 ASDF 仅在组件文件存在时才处理该组件文件(以便在组件文件尚不存在时不会生成错误)。

(asdf:defsystem "my-system"
  :components ((:file "utilities")
               (:file "temp-file" :depends-on ("utilities"))))

我的解决方法是使用读取器宏#。在 (probe-file "temp-file") 上，但无法使其工作。

Answer 1

我认为你真正想做的是让 ASDF 只是警告你，而不是在编译错误期间启动调试器。更改 *compile-file-warnings-behaviour* 和 *compile-file-failure-behaviour*，并读取 the section on error handling在手册中。

这个答案的其余部分是如何检查整个系统。您可以将可能要加载的文件打包到它们自己的系统中，并按照下面的方式执行此操作。

来自ASDF Manual section 6.3.8 .

6.3.8 Weakly depends on

We do NOT recommend you use this feature.

所以你无论如何都可以使用它。像这样:

(defpackage :foo-system
  (:use :cl :asdf))
(in-package :foo-system)
(defsystem foo
  :description "The main package that maybe loads bar if it exists."
  :weakly-depends-on (:bar)
  :components ((:file "foo")))

简单吧？

以下是他们的建议:

If you are tempted to write a system foo that weakly-depends-on a system bar, we recommend that you should instead write system foo in a parametric way, and offer some special variable and/or some hook to specialize its behaviour; then you should write a system foo+bar that does the hooking of things together.

我从未在野外见过其中的一个，可能是因为这样做会造成可怕的困惑。

(defpackage :bar-system
  (:use :cl :asdf))
(in-package :bar-system)
(defsystem bar
  :description "The package that maybe exists and is needed by foo."
  :components ((:file "bar")))

(defpackage :foo+bar-system
  (:use :cl :asdf))
(in-package :foo+bar-system)
(defsystem foo+bar
  :version      "0.1.0"
  :description  "Hook together foo and bar."
  :author       "Spenser Truex <web@spensertruex.com>"
  :serial       t
  :components ((:file "foo+bar")))

(defpackage :foo-system
  (:use :cl :asdf))
(in-package :foo-system)
(defsystem foo
  :description "The main package that maybe loads bar if it exists."
  :depends-on (:foo+bar)
  :components ((:file "foo")))