bon_macros/util/
ident.rs

1use crate::util::prelude::*;
2use ident_case::RenameRule;
3
4pub(crate) trait IdentExt {
5    /// Converts the ident (assumed to be in `snake_case`) to `PascalCase` without
6    /// preserving its span.
7    ///
8    /// Span loss is intentional to work around the semantic token type assignment
9    /// ambiguity that may be experienced by IDEs. For example, rust analyzer
10    /// assigns different colors to identifiers according to their semantic meaning.
11    ///
12    /// If identifiers with the same span were used in different contexts such as
13    /// in function name and struct name positions, then rust-analyzer would chose
14    /// the semantic meaning for syntax highlighting of the input identifier randomly
15    /// out of these two contexts.
16    ///
17    /// By not preserving the span, we can ensure that the semantic meaning of the
18    /// produced identifier won't influence the syntax highlighting of the original
19    /// identifier.
20    fn snake_to_pascal_case(&self) -> Self;
21
22    /// Same thing as `snake_to_pascal_case` but converts `PascalCase` to `snake_case`.
23    fn pascal_to_snake_case(&self) -> Self;
24
25    /// Creates a new ident with the given name and span. If the name starts with
26    /// `r#` then automatically creates a raw ident.
27    fn new_maybe_raw(name: &str, span: Span) -> Self;
28
29    /// Returns the name of the identifier stripping the `r#` prefix if it exists.
30    fn raw_name(&self) -> String;
31}
32
33impl IdentExt for syn::Ident {
34    fn snake_to_pascal_case(&self) -> Self {
35        // There are no pascal case keywords in Rust except for `Self`, which
36        // is anyway not allowed even as a raw identifier:
37        // https://internals.rust-lang.org/t/raw-identifiers-dont-work-for-all-identifiers/9094
38        //
39        // So no need to handle raw identifiers here.
40        let renamed = RenameRule::PascalCase.apply_to_field(self.raw_name());
41        Self::new(&renamed, Span::call_site())
42    }
43
44    fn pascal_to_snake_case(&self) -> Self {
45        let renamed = RenameRule::SnakeCase.apply_to_variant(self.raw_name());
46        Self::new_maybe_raw(&renamed, Span::call_site())
47    }
48
49    fn new_maybe_raw(name: &str, span: Span) -> Self {
50        // If the ident is already raw (starts with `r#`) then just create a raw ident.
51        if let Some(name) = name.strip_prefix("r#") {
52            return Self::new_raw(name, span);
53        }
54
55        // ..otherwise validate if it is a valid identifier.
56        // The `parse_str` method will return an error if the name is not a valid
57        // identifier.
58        if syn::parse_str::<Self>(name).is_ok() {
59            return Self::new(name, span);
60        }
61
62        // Try to make it a raw ident by adding `r#` prefix.
63        // This won't work for some keywords such as `super`, `crate`,
64        // `Self`, which are not allowed as raw identifiers
65        if syn::parse_str::<Self>(&format!("r#{name}")).is_ok() {
66            return Self::new_raw(name, span);
67        }
68
69        // As the final fallback add a trailing `_` to create a valid identifier
70        Self::new(&format!("{name}_"), span)
71    }
72
73    fn raw_name(&self) -> String {
74        let name = self.to_string();
75        if let Some(raw) = name.strip_prefix("r#") {
76            raw.to_owned()
77        } else {
78            name
79        }
80    }
81}
bon_macros/util/ident.rs

bon_macros/util/
ident.rs
