Merge pull request #8527 from roc-lang/fix-str-split-on

Fix semantics for `Str.split_on`

src/canonicalize/Expression.zig

@@ -827,9 +827,9 @@ pub const Expr = union(enum) {
                 .str_reserve => &.{ .consume, .borrow },
                 .str_release_excess_capacity => &.{.consume},
                 .str_join_with => &.{ .consume, .borrow }, // list consumed, separator borrowed
-                .str_split_on => &.{ .consume, .borrow },
 
                 // String operations - borrowing with seamless slice result (incref internally)
+                .str_split_on => &.{ .borrow, .borrow },
                 .str_to_utf8 => &.{.borrow},
                 .str_drop_prefix, .str_drop_suffix => &.{ .borrow, .borrow },
 

src/cli/test/fx_platform_test.zig

@@ -771,3 +771,45 @@ test "string literal pattern matching" {
     try testing.expect(has_alice);
     try testing.expect(has_bob);
 }
+
+test "multiline string split_on" {
+    // Tests splitting a multiline string and iterating over the lines.
+    // This is a regression test to ensure split_on works correctly with
+    // multiline strings and doesn't cause memory issues.
+    const allocator = testing.allocator;
+
+    try ensureRocBinary(allocator);
+
+    const run_result = try std.process.Child.run(.{
+        .allocator = allocator,
+        .argv = &[_][]const u8{
+            "./zig-out/bin/roc",
+            "test/fx/multiline_split_leak.roc",
+        },
+    });
+    defer allocator.free(run_result.stdout);
+    defer allocator.free(run_result.stderr);
+
+    switch (run_result.term) {
+        .Exited => |code| {
+            if (code != 0) {
+                std.debug.print("Run failed with exit code {}\n", .{code});
+                std.debug.print("STDOUT: {s}\n", .{run_result.stdout});
+                std.debug.print("STDERR: {s}\n", .{run_result.stderr});
+                return error.RunFailed;
+            }
+        },
+        else => {
+            std.debug.print("Run terminated abnormally: {}\n", .{run_result.term});
+            std.debug.print("STDOUT: {s}\n", .{run_result.stdout});
+            std.debug.print("STDERR: {s}\n", .{run_result.stderr});
+            return error.RunFailed;
+        },
+    }
+
+    // Verify the output contains lines from the multiline string
+    try testing.expect(std.mem.indexOf(u8, run_result.stdout, "This is a longer line number one") != null);
+    try testing.expect(std.mem.indexOf(u8, run_result.stdout, "This is a longer line number two") != null);
+    try testing.expect(std.mem.indexOf(u8, run_result.stdout, "L68") != null);
+    try testing.expect(std.mem.indexOf(u8, run_result.stdout, "The last line is here") != null);
+}

test/fx/multiline_split_leak.roc

@@ -0,0 +1,20 @@
+app [main!] { pf: platform "./platform/main.roc" }
+
+import pf.Stdout
+
+input =
+    \\This is a longer line number one
+    \\This is a longer line number two
+	\\L68
+	\\L30
+	\\R48
+	\\L5
+	\\R60
+	\\L55
+	\\L1
+	\\The last line is here
+
+main! = || {
+    for line in input.split_on("\n")
+    Stdout.line!(line)
+}

test/snapshots/repl/multiline_string_split_7_lines.md

@@ -0,0 +1,16 @@
+# META
+~~~ini
+description=Multiline string with 7 lines split - memory leak test
+type=repl
+~~~
+# SOURCE
+~~~roc
+» input = "L68\nL30\nR48\nL5\nR60\nL55\nL1"
+» input.split_on("\n")
+~~~
+# OUTPUT
+assigned `input`
+---
+["L68", "L30", "R48", "L5", "R60", "L55", "L1"]
+# PROBLEMS
+NIL