testgen: fix cli exit status and write logging

Author: Bao Zhiyuan

testgen/main.mbt

@@ -22,6 +22,21 @@ fn usage() -> String {
   text
 }
 
+///|
+fn write_generated_file(path : String, content : String) -> Unit {
+  let write_ok = try @fs.write_string_to_file(path, content) catch {
+    err => {
+      println("Error: failed to write \{path}: \{err}")
+      false
+    }
+  } noraise {
+    _ => true
+  }
+  if write_ok {
+    println("generated \{path}")
+  }
+}
+
 ///|
 fn normalized_args(args : Array[String]) -> Array[String] {
   if args.length() == 0 {
@@ -100,13 +115,7 @@ fn ensure_dune_file(project_root : String) -> Unit {
     #| (deps
     #|  (source_tree .)))
     #|
-  @fs.write_string_to_file(dune_path, dune_content) catch {
-    err => {
-      println("Error: failed to write \{dune_path}: \{err}")
-      return
-    }
-  }
-  println("generated \{dune_path}")
+  write_generated_file(dune_path, dune_content)
 }
 
 ///|
@@ -116,6 +125,7 @@ fn run(args : Array[String]) -> Unit {
     Error(msg) => {
       println("Error: \{msg}")
       println(usage())
+      @sys.exit(1)
     }
     Parsed(config) => {
       ensure_dune_file(config.project_root)
@@ -126,10 +136,7 @@ fn run(args : Array[String]) -> Unit {
       let files = render_cram_files(result)
       for file in files {
         let path = @path.Path::join(config.project_root, file.name).to_string()
-        @fs.write_string_to_file(path, file.content) catch {
-          err => println("Error: failed to write \{path}: \{err}")
-        }
-        println("generated \{path}")
+        write_generated_file(path, file.content)
       }
     }
   }

testgen/moon.pkg

@@ -7,6 +7,7 @@ import {
   "moonbitlang/parser/syntax" @syntax,
   "moonbitlang/x/fs" @fs,
   "moonbitlang/x/path" @path,
+  "moonbitlang/x/sys" @sys,
 }
 
 options(