annotation sometimes points at the line above the correct line

[BurntSushi]

Here is a repro program (note the assert to make it clear where the span is pointing):

use annotate_snippets::{Level, Renderer, Snippet};

fn main() {
    let source = "    \"\"\"Summary.\n\nDescription.\n\n    \"\"\"\n";
    assert_eq!(&source[17..], "Description.\n\n    \"\"\"\n");
    let src_annotation = Level::Error.span(17..17).label("D207");
    let snippet =
        Snippet::source(source).line_start(230).annotation(src_annotation);
    let message = Level::Error.title("").snippet(snippet);

    println!("{}", Renderer::plain().render(message));
}

The actual output:

error
    |
230 |     """Summary.
231 |
    | ^ D207
232 | Description.
233 |
234 |     """
    |

And the expected output:

error
    |
230 |     """Summary.
231 |
232 | Description.
    | ^ D207
233 |
234 |     """
    |

In annotate-snippets 0.9.2, the rendering targeted the right line, but the ^ is missing. Here's a repro program for that:

use annotate_snippets::{
    display_list::{DisplayList, FormatOptions},
    snippet::{AnnotationType, Slice, Snippet, SourceAnnotation},
};

fn main() {
    let source = "    \"\"\"Summary.\n\nDescription.\n\n    \"\"\"\n";
    let snippet = Snippet {
        title: None,
        footer: vec![],
        slices: vec![Slice {
            source,
            line_start: 230,
            origin: None,
            annotations: vec![SourceAnnotation {
                range: (17, 17),
                label: "D207",
                annotation_type: AnnotationType::Error,
            }],
            fold: false,
        }],
        opt: FormatOptions {
            color: false,
            anonymized_line_numbers: false,
            margin: None,
        },
    };
    println!("{message}", message = DisplayList::from(snippet));
}

And the output:

    |
230 |     """Summary.
231 |
232 | Description.
    |  D207
233 |
234 |     """
    |

[epage]

This looks like an empty span immediately before the start of a line. How is this different than #176?

[BurntSushi]

Ah right right. I think the whitespace made this look different to my brain, but you're absolutely right. I'll close in favor of #176.