fix(pretty): escape quoted/interpolated string output

Author: pchalamet

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to FScript are documented in this file.
 
 ## [Unreleased]
 
+- Escaped pretty-printed string values (including map string keys) so interpolated strings with embedded quotes render unambiguously in CLI/REPL output.
+
 ## [0.54.2]
 
 

src/FScript.Language/Pretty.fs

@@ -10,13 +10,21 @@ module Pretty =
             | _ -> acc
         loop [ firstArg ] body
 
+    let private escapeStringLiteral (value: string) =
+        value
+            .Replace("\\", "\\\\")
+            .Replace("\"", "\\\"")
+            .Replace("\r", "\\r")
+            .Replace("\n", "\\n")
+            .Replace("\t", "\\t")
+
     let rec valueToString v =
         match v with
         | VUnit -> "()"
         | VInt i -> string i
         | VFloat f -> string f
         | VBool b -> if b then "true" else "false"
-        | VString s -> sprintf "\"%s\"" s
+        | VString s -> sprintf "\"%s\"" (escapeStringLiteral s)
         | VList xs ->
             xs |> List.map valueToString |> String.concat ";" |> sprintf "[%s]"
         | VTuple xs ->
@@ -30,7 +38,7 @@ module Pretty =
         | VMap fields ->
             let mapKeyToString key =
                 match key with
-                | MKString s -> $"\"{s}\""
+                | MKString s -> $"\"{escapeStringLiteral s}\""
                 | MKInt i -> string i
             fields
             |> Map.toList

tests/FScript.Language.Tests/EvalTests.fs

@@ -508,6 +508,12 @@ type EvalTests () =
         | VString "missing" -> ()
         | _ -> Assert.Fail("Expected interpolation with string-literal placeholder expression")
 
+    [<Test>]
+    member _.``Evaluates interpolation containing escaped quotes around placeholder`` () =
+        match Helpers.eval "let value = \"'\"\n$\"Path=\\\"{value}\\\"\"" with
+        | VString "Path=\"'\"" -> ()
+        | _ -> Assert.Fail("Expected interpolation value with quoted placeholder content")
+
     [<Test>]
     member _.``Evaluates typeof for explicit recursive type`` () =
         match Helpers.eval "type rec Node = { Value: int; Next: Node option }\ntypeof Node" with

tests/FScript.Language.Tests/PrettyTests.fs

@@ -27,3 +27,15 @@ type PrettyTests () =
     [<Test>]
     member _.``Formats extern values with name and application progress`` () =
         Helpers.evalToString "print" |> should equal "<extern print>"
+
+    [<Test>]
+    member _.``Escapes quoted interpolation output in strings`` () =
+        Helpers.evalToString "let value = \"'\"\n$\"Path=\\\"{value}\\\"\"" |> should equal "\"Path=\\\"'\\\"\""
+
+    [<Test>]
+    member _.``Escapes special characters in rendered strings`` () =
+        Helpers.evalToString "\"a\\\"b\\\\c\\n\\t\"" |> should equal "\"a\\\"b\\\\c\\n\\t\""
+
+    [<Test>]
+    member _.``Escapes quoted map string keys`` () =
+        Helpers.evalToString "{ [\"a\\\"b\"] = 1 }" |> should equal "map { \"a\\\"b\" => 1 }"