如何捕获编译时异常？ [英] How to catch a compile-time exception?

问题描述

在Clojure中是否有可能捕获在编译时发生的异常？对于运行时异常，使用try / catch很容易，但是假设我有：

Is it possible in Clojure to catch an exception that occurs at compile time? Using try/catch is fine and easy for run-time exceptions, but suppose I have:

(defmacro will-throw-at-compile [] (assert false "it threw"))

(try (will-throw-at-compile) (catch Exception e "caught it"))

我找不到任何办法可以抓住这一点，但是抓不到。我也尝试过不同类型的异常类，这似乎不是问题。

I can't find any way to catch this, the catch never happens. I've tried different types of exception classes as well, doesn't seem to be the problem.

我还认为，由于上述尝试是运行时调用，使宏在编译时进行尝试：

I also thought that since the try above is a run-time call, making a macro to do the try at compile time:

(defmacro t [x] (try x (catch Exception e "caught it")))

也不起作用：

(t (will-throw-at-compile))

也许无法完成？

推荐答案

如果宏能够处理其自身的异常，则可以使其工作。将宏的大部分工作分解为一个函数：

You can make it work if the macro handles it's own exception. Break out the majority of the work of the macro into a function:

(defn thrower []
  (throw (Exception. "it threw")))

(defmacro will-throw 
  []
  (try 
    (thrower)
    (catch Exception e (println "caught it")))
  (println "leaving macro"))

(will-throw) 

运行此代码将导致：

> lein run
caught it
leaving macro

将所有宏功能转换为常规功能，因此可以将其称为&在编译时宏机制之外进行了测试。然后，您可以使用常规的单元测试，如下所示：

The idea is to put most or all of the macro functionality into a regular function, so it can be called & tested outside of the compile-time macro mechanism. Then you can use regular unit-tests like so:

(deftest t-thrower
  (is (thrown? Exception (thrower)))
  (println "t-thrower complete"))

> lein test
caught it
leaving macro

lein test tst.clj.core
t-thrower complete

Ran 1 tests containing 1 assertions.
0 failures, 0 errors.

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