Print missing no-eol in pretty test result

Summary:
This CL ensures Scrut suggest to add `(no-eol)` with the pretty renderer if it is missing.

# What?

Append ` (no-eol)` to unexpected output lines that do not end in a new-line in the pretty validation result renderer

# Why?

Before this CL, if a test output validation contained an `equal` rule (i.e. a comparison with a line that ends in a new-line) but expected a `no-eol` rule (i.e. a comparison with a line that does not end with a new-line), then the pretty rendere would provide:

```
1     | - There is no new line
   1  | + There is no new line
```

This was unclear and did not provide the test author with any actionable steps to fix the test. With this CL the output will now correctly show:

```
1     | - There is no new line
   1  | + There is no new line (no-eol)
```

Reviewed By: AndreasBackx

Differential Revision: D63902398

fbshipit-source-id: 0703165dc80b41e1fe32a837493ae320baf5f759

py/pytest/parsertest.py

@@ -61,7 +61,7 @@ def test_fail_on_invalid_exit_code(self) -> None:
         )
 
     def test_validation_invalid_input(self) -> None:
-        result = Output(b"Wrong", b"", 0)
+        result = Output(b"Wrong\n", b"", 0)
         ok, error = self._testcases()[0].validate(result, "the-location")
         self.assertEqual(False, ok)
         print(ok)

selftest/complex/no-eol/invalid.mdtest

@@ -0,0 +1,13 @@
+# A test where output does NOT end in new-line
+
+```scrut
+$ echo -n There is no new line
+There is no new line
+```
+
+# A test where output DOES end in new-line
+
+```scrut
+$ echo There is a new line
+There is a new line (no-eol)
+```

selftest/complex/no-eol/pretty-renderer-shows-no-eol.md

@@ -0,0 +1,36 @@
+# Test that Scrut proposes noeol if a line does not match for that reason
+
+This test validates that if the user writes a Scrut test where they use an equal-rule (i.e. with ending new-line
+character) but the output does not end in a new-line, then Scrut prints the missing `(no-eol)` suffix.
+
+## No-EOL is proposed in the pretty print of the failed test
+
+```scrut
+$ "$SCRUT_BIN" test --renderer pretty --match-markdown "*.mdtest" "$TESTDIR/invalid.mdtest"
+// =============================================================================
+// @ .*[/\\]invalid\.mdtest:4 (regex)
+// -----------------------------------------------------------------------------
+// # A test where output does NOT end in new-line
+// -----------------------------------------------------------------------------
+// $ echo -n There is no new line
+// =============================================================================
+
+1     | - There is no new line
+   1  | + There is no new line (no-eol) (equal)
+
+
+// =============================================================================
+// @ .*[/\\]invalid\.mdtest:11 (regex)
+// -----------------------------------------------------------------------------
+// # A test where output DOES end in new-line
+// -----------------------------------------------------------------------------
+// $ echo There is a new line
+// =============================================================================
+
+1     | - There is a new line (no-eol) (equal)
+   1  | + There is a new line
+
+
+Result: 1 file(s) with 2 test(s): 0 succeeded, 2 failed and 0 skipped
+[50]
+```

selftest/complex/no-eol/update-generates-no-eol.md

@@ -0,0 +1,22 @@
+# Test that Scrut proposes noeol if a line does not match for that reason
+
+This test validates that if the user writes a Scrut test where they use an equal-rule (i.e. with ending new-line
+character) but the output does not end in a new-line, then Scrut prints the missing `(no-eol)` suffix.
+
+
+```scrut
+$ cp "$TESTDIR/invalid.mdtest" "$(pwd)/invalid.mdtest"
+```
+
+## No-EOL is proposed in the pretty print of the failed test
+
+```scrut
+$ "$SCRUT_BIN" update --match-markdown "*.mdtest" "$(pwd)/invalid.mdtest"
+Result: 1 file(s) of which 1 updated, 0 skipped and 0 unchanged
+```
+
+## Generated file matches valid result
+
+```scrut
+$ diff "$(pwd)/invalid.mdtest.new" "$TESTDIR/valid.mdtest"
+```

selftest/complex/no-eol/valid.mdtest

@@ -0,0 +1,13 @@
+# A test where output does NOT end in new-line
+
+```scrut
+$ echo -n There is no new line
+There is no new line (no-eol)
+```
+
+# A test where output DOES end in new-line
+
+```scrut
+$ echo There is a new line
+There is a new line
+```

src/diff.rs

@@ -13,6 +13,7 @@ use serde::Serialize;
 
 use crate::expectation::Expectation;
 use crate::lossy_string;
+use crate::newline::BytesNewline;
 use crate::newline::SplitLinesByNewline;
 
 /// Compares [`crate::output::Output`]s of [`crate::executors::executor::Executor`]
@@ -455,7 +456,14 @@ impl Debug for DiffLine {
             }
             Self::UnexpectedLines { lines } => {
                 for (index, line) in lines {
-                    write!(f, "     {:04} | + {}", index + 1, lossy_string!(line))?;
+                    let eol = (line.as_ref() as &[u8]).ends_in_newline();
+                    write!(
+                        f,
+                        "     {:04} | + {}{}",
+                        index + 1,
+                        lossy_string!(line),
+                        if eol { "" } else { " (no-eol)" }
+                    )?;
                 }
                 Ok(())
             }

src/newline.rs

@@ -27,6 +27,9 @@ pub(crate) trait BytesNewline {
 
     /// Returns byte slice that ends in newline character(s)
     fn assure_newline(&self) -> Cow<'_, [u8]>;
+
+    /// Return bool whether ends in new line
+    fn ends_in_newline(&self) -> bool;
 }
 
 impl BytesNewline for &[u8] {
@@ -46,6 +49,10 @@ impl BytesNewline for &[u8] {
         updated.push(b'\n');
         updated.into()
     }
+
+    fn ends_in_newline(&self) -> bool {
+        ends_in_newline(self)
+    }
 }
 
 fn ends_in_newline(data: &[u8]) -> bool {

src/renderers/pretty.rs

@@ -17,6 +17,7 @@ use crate::diff::Diff;
 use crate::diff::DiffLine;
 use crate::escaping::strip_colors;
 use crate::formatln;
+use crate::newline::BytesNewline;
 use crate::newline::StringNewline;
 use crate::outcome::Outcome;
 use crate::testcase::TestCaseError;
@@ -240,9 +241,17 @@ impl ErrorRenderer for PrettyColorRenderer {
                 }
                 DiffLine::UnexpectedLines { lines } => {
                     lines.iter().for_each(|(line_index, line)| {
+                        let eol = (line.as_ref() as &[u8]).ends_in_newline();
+                        let line = if !eol {
+                            let mut line = line.clone();
+                            line.extend(b" (no-eol)");
+                            line
+                        } else {
+                            line.to_owned()
+                        };
                         let line = outcome
                             .escaping
-                            .escaped_expectation(line)
+                            .escaped_expectation(&line)
                             .higlight_tailing_spaces();
                         last_error_index = Some(diff_index);
                         output.push_str(