aoc_parse/
error.rs

1use thiserror::Error;
2
3#[derive(Clone, Debug, Error)]
4enum ParseErrorReason {
5    #[error("extra unparsed text after match")]
6    Extra,
7    #[error("line() can't match here because this is not at the start of a line")]
8    NotAtLineStart,
9    #[error("section() can't match here because this is not at the start of a section")]
10    NotAtSectionStart,
11    #[error("line(pattern) matched part of the line, but not all of it")]
12    LineExtra,
13    #[error("section(pattern) matched part of the section, but not all of it")]
14    SectionExtra,
15    #[error("expected {0}")]
16    Expected(String),
17    #[error("failed to parse {input:?} as type {type_name}: {message}")]
18    FromStrFailed {
19        input: String,
20        type_name: &'static str,
21        message: String,
22    },
23}
24
25/// An error happened while trying to parse puzzle input or convert the matched
26/// characters to a Rust value.
27#[derive(Clone)]
28pub struct ParseError {
29    /// The puzzle input we were trying to parse.
30    pub source: String,
31
32    /// The byte offset into `source` where the elves detected a problem and
33    /// could not go any further. This is guaranteed to be a char boundary in
34    /// `source`.
35    pub location: usize,
36
37    reason: ParseErrorReason,
38}
39
40impl std::fmt::Display for ParseError {
41    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
42        let reason = &self.reason;
43        let source = &self.source;
44        if self.location == source.len() {
45            write!(f, "{reason} at end of input")
46        } else {
47            let p = self.location.min(source.len());
48            let line_start = match source[..p].rfind('\n') {
49                Some(i) => i + 1,
50                None => 0,
51            };
52            let line_num = source[..line_start].chars().filter(|c| *c == '\n').count() + 1;
53            let column_num = source[line_start..p].chars().count() + 1;
54            write!(f, "{reason} at line {line_num} column {column_num}")
55        }
56    }
57}
58
59// aoc_runner prints the Debug form of errors, instead of the human-readable
60// Display form. Work around this by adding the Display form to ParseError's
61// Debug output.
62impl std::fmt::Debug for ParseError {
63    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
64        f.debug_struct("ParseError")
65            .field("source", &self.source)
66            .field("location", &self.location)
67            .field("reason", &self.reason)
68            .field("summary", &format!("{self}"))
69            .finish()
70    }
71}
72
73impl std::error::Error for ParseError {}
74
75impl ParseError {
76    fn new(source: &str, location: usize, reason: ParseErrorReason) -> Self {
77        assert!(source.is_char_boundary(location));
78        ParseError {
79            source: source.to_string(),
80            location,
81            reason,
82        }
83    }
84
85    pub(crate) fn new_extra(source: &str, location: usize) -> Self {
86        Self::new(source, location, ParseErrorReason::Extra)
87    }
88
89    pub(crate) fn new_bad_line_start(source: &str, location: usize) -> Self {
90        Self::new(source, location, ParseErrorReason::NotAtLineStart)
91    }
92
93    pub(crate) fn new_bad_section_start(source: &str, location: usize) -> Self {
94        Self::new(source, location, ParseErrorReason::NotAtSectionStart)
95    }
96
97    pub(crate) fn new_line_extra(source: &str, location: usize) -> Self {
98        Self::new(source, location, ParseErrorReason::LineExtra)
99    }
100
101    pub(crate) fn new_section_extra(source: &str, location: usize) -> Self {
102        Self::new(source, location, ParseErrorReason::SectionExtra)
103    }
104
105    pub(crate) fn new_expected(source: &str, location: usize, expected: &str) -> Self {
106        Self::new(
107            source,
108            location,
109            ParseErrorReason::Expected(expected.to_string()),
110        )
111    }
112
113    pub(crate) fn new_from_str_failed(
114        source: &str,
115        start: usize,
116        end: usize,
117        type_name: &'static str,
118        message: String,
119    ) -> Self {
120        Self::new(
121            source,
122            start,
123            ParseErrorReason::FromStrFailed {
124                input: source[start..end].to_string(),
125                type_name,
126                message,
127            },
128        )
129    }
130
131    /// This is used when a subparser is used on a slice of the original
132    /// string. If the subparse fails, the error location is a position within
133    /// the slice. This can be used, passing the start offset of the slice, to
134    /// convert that to a position within the original string.
135    pub(crate) fn adjust_location(mut self, full_source: &str, offset: usize) -> Self {
136        self.source = full_source.to_string();
137        self.location += offset;
138        self
139    }
140}
141
142pub(crate) type Result<T, E = ParseError> = std::result::Result<T, E>;
aoc_parse/error.rs

aoc_parse/
error.rs
