Validate static asserts

[Ali Çehreli]

On 9/9/22 10:35, Dennis wrote:
 > On Friday, 9 September 2022 at 16:41:54 UTC, Andrey Zherikov wrote:
 >> What's about new `compileOutput` trait that returns compiler output?
 >> ```d
 >> static assert(__traits(compileOutput, { <my code> }) == "message");
 >> ```
 >
 > As a compiler dev, that sounds terrifying. It would make basically every
 > change to dmd a breaking change.

For that very reason, I wrote the function 'assertErrorStringContains()' 
a couple of days ago to ensure *my* strings were in the output:

A precondition:

     void test_1(int i)
     in (i > 0, fooError("The value must be positive", i, 42))
     {
         // ...
     }

A unit test that ensures it fails and checks string pieces appear in the 
output:

     /*
         The .msg text of the error contains both the error string and 
the data
         that is included in the error.
     */
     assertErrorStringContains(() => test_1(-1), [ "The value must be 
positive",
                                                   "-1, 42" ]);
Here is assertErrorStringContains:

     // Assert that the expression throws an Error object and that its 
string
     // representation contains all expected strings.
     void assertErrorStringContains(void delegate() expr, string[] expected)
     {
         bool thrown = false;

         try
         {
             expr();

         }
         catch (Error err)
         {
             thrown = true;

             import std.algorithm : any, canFind, splitter;
             import std.conv : to;
             import std.format : format;

             auto lines = err.to!string.splitter('\n');
             foreach (exp; expected)
             {
                 assert(lines.any!(line => line.canFind(exp)),
                        format!"Failed to find \"%s\" in the output: 
%-(\n  |%s%)"(
                            exp, lines));
             }
         }

         assert(thrown);
     }

Ali