compiler: move prelude files to tools/preludes/

tools/preludes/tests_assertions.v

@@ -0,0 +1,36 @@
+module main
+
+import os
+import term
+// //////////////////////////////////////////////////////////////////
+// / This file will get compiled as part of the main program,
+// / for a _test.v file.
+// / The methods defined here are called back by the test program's
+// / assert statements, on each success/fail. The goal is to make
+// / customizing the look & feel of the assertions results easier,
+// / since it is done in normal V code, instead of in embedded C ...
+// //////////////////////////////////////////////////////////////////
+fn cb_assertion_failed(filename string, line int, sourceline string, funcname string) {
+	color_on := term.can_show_color_on_stderr()
+	use_relative_paths := match os.getenv('VERROR_PATHS') {
+		'absolute'{
+			false
+		}
+		else {
+			true}
+	}
+	final_filename := if use_relative_paths { filename } else { os.realpath(filename) }
+	final_funcname := funcname.replace('main__', '').replace('__', '.')
+	mut fail_message := 'FAILED assertion'
+	if color_on {
+		fail_message = term.bold(term.red(fail_message))
+	}
+	eprintln('$final_filename:$line: $fail_message')
+	eprintln('Function: $final_funcname')
+	eprintln('Source  : $sourceline')
+}
+
+fn cb_assertion_ok(filename string, line int, sourceline string, funcname string) {
+	// do nothing for now on an OK assertion
+	// println('OK ${line:5d}|$sourceline ')
+	}