mailparsing/
nom_utils.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
use nom::error::{ContextError, ErrorKind};
use nom_locate::LocatedSpan;
use std::fmt::{Debug, Write};

pub(crate) type Span<'a> = LocatedSpan<&'a str>;
pub(crate) type IResult<'a, A, B> = nom::IResult<A, B, ParseError<Span<'a>>>;

pub fn make_span(s: &str) -> Span {
    Span::new(s)
}

#[derive(Debug)]
pub enum ParseErrorKind {
    Context(&'static str),
    Char(char),
    Nom(ErrorKind),
    External { kind: ErrorKind, reason: String },
}

#[derive(Debug)]
pub struct ParseError<I: Debug> {
    pub errors: Vec<(I, ParseErrorKind)>,
}

impl<I: Debug> ContextError<I> for ParseError<I> {
    fn add_context(input: I, ctx: &'static str, mut other: Self) -> Self {
        other.errors.push((input, ParseErrorKind::Context(ctx)));
        other
    }
}

impl<I: Debug> nom::error::ParseError<I> for ParseError<I> {
    fn from_error_kind(input: I, kind: ErrorKind) -> Self {
        Self {
            errors: vec![(input, ParseErrorKind::Nom(kind))],
        }
    }

    fn append(input: I, kind: ErrorKind, mut other: Self) -> Self {
        other.errors.push((input, ParseErrorKind::Nom(kind)));
        other
    }

    fn from_char(input: I, c: char) -> Self {
        Self {
            errors: vec![(input, ParseErrorKind::Char(c))],
        }
    }
}

impl<I: Debug, E: std::fmt::Display> nom::error::FromExternalError<I, E> for ParseError<I> {
    fn from_external_error(input: I, kind: ErrorKind, err: E) -> Self {
        Self {
            errors: vec![(
                input,
                ParseErrorKind::External {
                    kind,
                    reason: format!("{err:#}"),
                },
            )],
        }
    }
}

pub fn make_context_error<'a, S: Into<String>>(
    input: Span<'a>,
    reason: S,
) -> nom::Err<ParseError<Span<'a>>> {
    nom::Err::Error(ParseError {
        errors: vec![(
            input,
            ParseErrorKind::External {
                kind: nom::error::ErrorKind::Fail,
                reason: reason.into(),
            },
        )],
    })
}

pub fn explain_nom(input: Span, err: nom::Err<ParseError<Span<'_>>>) -> String {
    match err {
        nom::Err::Error(e) => {
            let mut result = String::new();
            for (i, (span, kind)) in e.errors.iter().enumerate() {
                if input.is_empty() {
                    match kind {
                        ParseErrorKind::Char(c) => {
                            write!(&mut result, "{i}: expected '{c}', got empty input\n\n")
                        }
                        ParseErrorKind::Context(s) => {
                            write!(&mut result, "{i}: in {s}, got empty input\n\n")
                        }
                        ParseErrorKind::External { kind, reason } => {
                            write!(&mut result, "{i}: {reason} {kind:?}, got empty input\n\n")
                        }
                        ParseErrorKind::Nom(e) => {
                            write!(&mut result, "{i}: in {e:?}, got empty input\n\n")
                        }
                    }
                    .ok();
                    continue;
                }

                let line_number = span.location_line();
                let line = std::str::from_utf8(span.get_line_beginning())
                    .unwrap_or("<INVALID: line slice is not utf8!>");
                // Remap \t in particular, because it can render as multiple
                // columns and defeat the column number calculation provided
                // by the Span type
                let line: String = line
                    .chars()
                    .map(|c| match c {
                        '\t' => '\u{2409}',
                        '\r' => '\u{240d}',
                        '\n' => '\u{240a}',
                        _ => c,
                    })
                    .collect();
                let column = span.get_utf8_column();
                let mut caret = " ".repeat(column.saturating_sub(1));
                caret.push('^');
                for _ in 1..span.fragment().len() {
                    caret.push('_')
                }

                match kind {
                    ParseErrorKind::Char(expected) => {
                        if let Some(actual) = span.fragment().chars().next() {
                            write!(
                                &mut result,
                                "{i}: at line {line_number}:\n\
                                    {line}\n\
                                    {caret}\n\
                                    expected '{expected}', found {actual}\n\n",
                            )
                        } else {
                            write!(
                                &mut result,
                                "{i}: at line {line_number}:\n\
                                    {line}\n\
                                    {caret}\n\
                                    expected '{expected}', got end of input\n\n",
                            )
                        }
                    }
                    ParseErrorKind::Context(context) => {
                        write!(
                            &mut result,
                            "{i}: at line {line_number}, in {context}:\n\
                                {line}\n\
                                {caret}\n\n",
                        )
                    }
                    ParseErrorKind::External { kind, reason } => {
                        write!(
                            &mut result,
                            "{i}: at line {line_number}, {reason} {kind:?}:\n\
                                {line}\n\
                                {caret}\n\n",
                        )
                    }
                    ParseErrorKind::Nom(nom_err) => {
                        write!(
                            &mut result,
                            "{i}: at line {line_number}, in {nom_err:?}:\n\
                                {line}\n\
                                {caret}\n\n",
                        )
                    }
                }
                .ok();
            }
            result
        }
        _ => format!("{err:#}"),
    }
}