Consistent break after string constant argument

CHANGES.md

@@ -15,6 +15,7 @@ profile. This started with version 0.26.0.
 
 - Remove trailing space inside a wrapping empty signature (#2443, @Julow)
 - Fix extension-point spacing in structures (#2450, @Julow)
+- \* Consistent break after string constant argument (#2453, @Julow)
 
 ## 0.26.1 (2023-09-15)
 

lib/Fmt_ast.ml

@@ -1467,15 +1467,15 @@ and fmt_args_grouped ?epi:(global_epi = noop) c ctx args =
       | Pexp_fun _ | Pexp_function _ -> Some false
       | _ -> None
     in
-    let epi =
-      match (lbl, last) with
-      | _, true -> None
-      | Nolabel, _ -> Some (fits_breaks "" ~hint:(1000, -1) "")
-      | _ -> Some (fits_breaks "" ~hint:(1000, -3) "")
+    let break_after =
+      match (ast.pexp_desc, c.conf.fmt_opts.break_string_literals.v) with
+      | Pexp_constant _, `Auto when not last ->
+          fits_breaks "" ~hint:(1000, -2) ""
+      | _ -> noop
     in
     hovbox
       (Params.Indent.fun_args_group c.conf ~lbl ast)
-      (fmt_label_arg c ?box ?epi (lbl, xarg))
+      (fmt_label_arg c ?box (lbl, xarg) $ break_after)
     $ fmt_if_k (not last) (break_unless_newline 1 0)
   in
   let fmt_args ~first ~last args =

test/passing/tests/break_string_literals-never.ml.err

@@ -3,3 +3,5 @@ Warning: tests/break_string_literals.ml:7 exceeds the margin
 Warning: tests/break_string_literals.ml:11 exceeds the margin
 Warning: tests/break_string_literals.ml:48 exceeds the margin
 Warning: tests/break_string_literals.ml:51 exceeds the margin
+Warning: tests/break_string_literals.ml:63 exceeds the margin
+Warning: tests/break_string_literals.ml:68 exceeds the margin

test/passing/tests/break_string_literals-never.ml.ref

@@ -58,3 +58,13 @@ let _ = "abc@,def\n\n ghi"
 let _ = "abc@,def\n\n"
 
 let _ = "abc@,def@\n\n"
+
+let _ =
+  Pp.textf
+    "Failed to parse environment variable: %s=%s\nPermitted values: if-exists always never\nDefault: %s"
+    var v (to_string default)
+
+let _ =
+  Pp.textf
+    "Failed to parse environment variable: %s=%s Permitted values: if-exists always never Default: %s"
+    var v (to_string default)

test/passing/tests/break_string_literals.ml

@@ -69,3 +69,17 @@ let _ = "abc@,def\n\nghi"
 let _ = "abc@,def\n\n ghi"
 let _ = "abc@,def\n\n"
 let _ = "abc@,def@\n\n"
+
+let _ =
+  Pp.textf
+    "Failed to parse environment variable: %s=%s\n\
+     Permitted values: if-exists always never\n\
+     Default: %s"
+    var v (to_string default)
+
+let _ =
+  Pp.textf
+    "Failed to parse environment variable: %s=%s \
+     Permitted values: if-exists always never \
+     Default: %s"
+    var v (to_string default)

test/passing/tests/break_string_literals.ml.ref

@@ -92,3 +92,16 @@ let _ = "abc@,def\n\n ghi"
 let _ = "abc@,def\n\n"
 
 let _ = "abc@,def@\n\n"
+
+let _ =
+  Pp.textf
+    "Failed to parse environment variable: %s=%s\n\
+     Permitted values: if-exists always never\n\
+     Default: %s"
+    var v (to_string default)
+
+let _ =
+  Pp.textf
+    "Failed to parse environment variable: %s=%s Permitted values: \
+     if-exists always never Default: %s"
+    var v (to_string default)

test/passing/tests/js_args.ml.ref

@@ -33,7 +33,8 @@ let () =
   messages :=
     Message_store.create (Session_id.of_string "")
       (* Tuareg indents these lines too far to the left. *)
-      "herd-retransmitter" Message_store.Message_size.Byte
+      "herd-retransmitter"
+      Message_store.Message_size.Byte
 
 let () =
   raise