add production mode tests

Due to the inability to detect warnings in REPL tests, I implemented running something very similar, but with the -prod flag enabled.
(See https://github.com/vlang/v/pull/2536)

There is also a minor change in os.walk_ext to not add duplicated path separators:
/path//file.ext -> /path/file.ext

vlib/compiler/tests/prod/.gitignore

@@ -0,0 +1,2 @@
+/*.prod
+/*.result.txt

vlib/compiler/tests/prod/assoc.prod.v

@@ -0,0 +1,14 @@
+struct MyStruct {
+    s string
+}
+fn new_st() MyStruct {
+    return MyStruct{}
+}
+fn get_st() MyStruct {
+    r := new_st() 
+    return {r|s:'6'}
+}
+fn main() {
+    s := get_st()
+    println(s)
+}

vlib/compiler/tests/prod/assoc.prod.v.expected.txt

@@ -0,0 +1,3 @@
+{
+	s: 6
+}

vlib/compiler/tests/prod_test.v

@@ -0,0 +1,29 @@
+// Build and run files in ./prod/ folder, comparing their output to *.expected.txt files.
+// (Similar to REPL tests, but in -prod mode.)
+
+// import os
+import compiler.tests.repl.runner
+import benchmark
+
+fn test_all_v_prod_files() {
+	// TODO: Fix running this test on Windows:
+	$if !windows {
+		options := runner.new_prod_options()
+		mut bmark := benchmark.new_benchmark()
+		for file in options.files {
+			// println('file:$file')
+			bmark.step()
+			fres := runner.run_prod_file(options.wd, options.vexec, file) or {
+				bmark.fail()
+				eprintln( bmark.step_message(err) )
+				assert false
+				continue
+			}
+			bmark.ok()
+			println( bmark.step_message(fres) )
+			assert true
+		}
+		bmark.stop()
+		println( bmark.total_message('total time spent running PROD files') )
+	}
+}

vlib/compiler/tests/repl/repl_test.v

@@ -3,7 +3,7 @@ import compiler.tests.repl.runner
 import benchmark
 
 fn test_the_v_compiler_can_be_invoked() {
-	vexec := runner.full_path_to_v()
+	vexec := runner.full_path_to_v(5)
 	println('vexecutable: $vexec')
 	assert vexec != ''
 

vlib/compiler/tests/repl/runner/runner.v

@@ -9,9 +9,13 @@ pub:
 	files []string
 }
 
-pub fn full_path_to_v() string {
-	vname  := if os.user_os() == 'windows' { 'v.exe' } else { 'v' }
-	vexec := os.dir(os.dir(os.dir(os.dir(os.dir( os.executable() ))))) + os.path_separator + vname
+pub fn full_path_to_v(dirs_in int) string {
+	vname := if os.user_os() == 'windows' { 'v.exe' } else { 'v' }
+	mut path := os.executable()
+	for i := 0; i < dirs_in; i++ {
+		path = os.dir(path)
+	}
+	vexec := path + os.path_separator + vname
 	/*
 	args := os.args
 	vreal  := os.realpath('v')
@@ -75,9 +79,42 @@ $diff
 	}
 }
 
+pub fn run_prod_file(wd string, vexec string, file string) ?string {
+	file_expected := '${file}.expected.txt'
+	f_expected_content := os.read_file(file_expected) or { return error('Could not read file $file') }
+	expected_content := f_expected_content.replace('\r', '')		
+
+	cmd := '"$vexec" -prod run "$file"'
+	r := os.exec(cmd) or {
+		return error('Could not execute: $cmd')
+	}
+
+	if r.exit_code != 0 {
+		return error('$cmd return exit code: $r.exit_code')
+	}
+
+	result := r.output.replace('\r','')
+
+	if result != expected_content {
+		file_result   := '${file}.result.txt'
+		os.write_file( file_result, result )
+		diff := diff_files( file_result, file_expected )
+		return error('Difference found in test: $file
+====> Got      :
+|$result|
+====> Expected :
+|$expected_content|
+====> Diff     :
+$diff
+		')
+	} else {
+		return 'Prod file $file is OK'
+	}
+}
+
 pub fn new_options() RunnerOptions {
 	wd := os.getwd() + os.path_separator
-	vexec := full_path_to_v()
+	vexec := full_path_to_v(5)
 	mut files := []string
 	if os.args.len > 1 {
 		files = os.args[1..]
@@ -91,3 +128,19 @@ pub fn new_options() RunnerOptions {
 	}
 }
 
+pub fn new_prod_options() RunnerOptions {
+	wd := os.getwd() + os.path_separator
+	vexec := full_path_to_v(4)
+	mut files := []string
+	if os.args.len > 1 {
+		files = os.args[1..]
+	} else {
+		files = os.walk_ext(wd, '.prod.v')
+	}
+	return RunnerOptions {
+		wd: wd
+		vexec: vexec
+		files: files
+	}
+}
+

vlib/os/os.v

@@ -856,11 +856,12 @@ pub fn walk_ext(path, ext string) []string {
 	}
 	mut files := os.ls(path) or { panic(err) }
 	mut res := []string
+	separator := if path.ends_with(path_separator) { '' } else { path_separator}
 	for i, file in files {
 		if file.starts_with('.') {
 			continue
 		}
-		p := path + path_separator + file
+		p := path + separator + file
 		if os.is_dir(p) {
 			res << walk_ext(p, ext)
 		}