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

use syn::parse::{Parse, ParseStream};
use syn::{parenthesized, punctuated::Punctuated};
use syn::{token, Token};

/// This struct is intented to represent the contents of the `#[pgx]` attribute when parsed.
///
/// The intended usage is to parse an `Attribute`, then use `attr.parse_args::<PgxAttribute>()?` to
/// parse the contents of the attribute into this struct.
///
/// We use this rather than `Attribute::parse_meta` because it is not supported to parse bare paths
/// as values of a `NameValueMeta`, and we want to support that to avoid conflating SQL strings with
/// paths-as-strings. We re-use as much of the standard `parse_meta` structure types as possible though.
pub struct PgxAttribute {
    pub args: Vec<PgxArg>,
}

impl Parse for PgxAttribute {
    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
        let parser = Punctuated::<PgxArg, Token![,]>::parse_terminated;
        let punctuated = input.call(parser)?;
        let args = punctuated
            .into_pairs()
            .map(|p| p.into_value())
            .collect::<Vec<_>>();
        Ok(Self { args })
    }
}

/// This enum is akin to `syn::Meta`, but supports a custom `NameValue` variant which allows
/// for bare paths in the value position.
pub enum PgxArg {
    Path(syn::Path),
    List(syn::MetaList),
    NameValue(NameValueArg),
}

impl Parse for PgxArg {
    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
        let path = input.parse::<syn::Path>()?;
        if input.peek(token::Paren) {
            let content;
            Ok(Self::List(syn::MetaList {
                path,
                paren_token: parenthesized!(content in input),
                nested: content.parse_terminated(syn::NestedMeta::parse)?,
            }))
        } else if input.peek(Token![=]) {
            Ok(Self::NameValue(NameValueArg {
                path,
                eq_token: input.parse()?,
                value: input.parse()?,
            }))
        } else {
            Ok(Self::Path(path))
        }
    }
}

/// This struct is akin to `syn::NameValueMeta`, but allows for more than just `syn::Lit` as a value.
pub struct NameValueArg {
    pub path: syn::Path,
    pub eq_token: syn::token::Eq,
    pub value: ArgValue,
}

/// This is the type of a value that can be used in the value position of a `name = value` attribute argument.
pub enum ArgValue {
    Path(syn::Path),
    Lit(syn::Lit),
}

impl Parse for ArgValue {
    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
        if input.peek(syn::Lit) {
            return Ok(Self::Lit(input.parse()?));
        }

        Ok(Self::Path(input.parse()?))
    }
}