# lib.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/paste-impl-0.1.18/src/lib.rs`.
Keywords: rust, rustlang, rust-lang

      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
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262
    263
    264
    265
    266
    267
    268
    269
    270
    271
    272
    273
    274
    275
    276
    277
    278
    279
    280
    281
    282
    283
    284
    285
    286
    287
    288
    289
    290
    291
    292
    293
    294
    295
    296
    297
    298
    299
    300
    301
    302
    303
    304
    305
    306
    307
    308
    309
    310
    311
    312
    313
    314
    315
    316
    317
    318
    319
    320
    321
    322
    323
    324
    325
    326
    327
    328
    329
    330
    331
    332
    333
    334
    335
    336
    337
    338
    339
    340
    341
    342
    343
    344
    345
    346
    347
    348
    349
    350
    351
    352
    353
    354
    355
    356
    357
    358
    359
    360
    361
    362
    363
    364
    365
    366
    367
    368
    369
    370
    371
    372
    373
    374
    375
    376
    377
    378
    379
    380
    381
    382
    383
    384
    385
    386
    387
    388
    389
    390
    391
    392
    393
    394
    395
    396
    397
    398
    399
    400
    401
    402
    403
    404
    405
    406
    407
    408
    409
    410
    411
    412
    413
    414
    415
    416
    417
    418
    419
    420
    421
    422
    423
    424
    425
    426
    427
    428
    429
    430
    431
    432
    433
    434
    435
    436
    437
    438
    439
    440
    441
    442
    443

    extern crate proc_macro;

    mod enum_hack;
    mod error;

    use crate::error::{Error, Result};
    use proc_macro::{
        token_stream, Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree,
    };
    use proc_macro_hack::proc_macro_hack;
    use std::iter::{self, FromIterator, Peekable};
    use std::panic;

    #[proc_macro]
    pub fn item(input: TokenStream) -> TokenStream {
        expand_paste(input)
    }

    #[proc_macro]
    pub fn item_with_macros(input: TokenStream) -> TokenStream {
        enum_hack::wrap(expand_paste(input))
    }

    #[proc_macro_hack]
    pub fn expr(input: TokenStream) -> TokenStream {
        TokenStream::from(TokenTree::Group(Group::new(
            Delimiter::Brace,
            expand_paste(input),
        )))
    }

    #[doc(hidden)]
    #[proc_macro_derive(EnumHack)]
    pub fn enum_hack(input: TokenStream) -> TokenStream {
        enum_hack::extract(input)
    }

    fn expand_paste(input: TokenStream) -> TokenStream {
        let mut contains_paste = false;
        match expand(input, &mut contains_paste) {
            Ok(expanded) => expanded,
            Err(err) => err.to_compile_error(),
        }
    }

    fn expand(input: TokenStream, contains_paste: &mut bool) -> Result<TokenStream> {
        let mut expanded = TokenStream::new();
        let (mut prev_colon, mut colon) = (false, false);
        let mut prev_none_group = None::<Group>;
        let mut tokens = input.into_iter().peekable();
        loop {
            let token = tokens.next();
            if let Some(group) = prev_none_group.take() {
                if match (&token, tokens.peek()) {
                    (Some(TokenTree::Punct(fst)), Some(TokenTree::Punct(snd))) => {
                        fst.as_char() == ':' && snd.as_char() == ':' && fst.spacing() == Spacing::Joint
                    }
                    _ => false,
                } {
                    expanded.extend(group.stream());
                    *contains_paste = true;
                } else {
                    expanded.extend(iter::once(TokenTree::Group(group)));
                }
            }
            match token {
                Some(TokenTree::Group(group)) => {
                    let delimiter = group.delimiter();
                    let content = group.stream();
                    let span = group.span();
                    if delimiter == Delimiter::Bracket && is_paste_operation(&content) {
                        let segments = parse_bracket_as_segments(content, span)?;
                        let pasted = paste_segments(span, &segments)?;
                        expanded.extend(pasted);
                        *contains_paste = true;
                    } else if is_none_delimited_flat_group(delimiter, &content) {
                        expanded.extend(content);
                        *contains_paste = true;
                    } else {
                        let mut group_contains_paste = false;
                        let nested = expand(content, &mut group_contains_paste)?;
                        let group = if group_contains_paste {
                            let mut group = Group::new(delimiter, nested);
                            group.set_span(span);
                            *contains_paste = true;
                            group
                        } else {
                            group.clone()
                        };
                        if delimiter != Delimiter::None {
                            expanded.extend(iter::once(TokenTree::Group(group)));
                        } else if prev_colon {
                            expanded.extend(group.stream());
                            *contains_paste = true;
                        } else {
                            prev_none_group = Some(group);
                        }
                    }
                    prev_colon = false;
                    colon = false;
                }
                Some(other) => {
                    match &other {
                        TokenTree::Punct(punct) if punct.as_char() == ':' => {
                            prev_colon = colon;
                            colon = punct.spacing() == Spacing::Joint;
                        }
                        _ => {
                            prev_colon = false;
                            colon = false;
                        }
                    }
                    expanded.extend(iter::once(other));
                }
                None => return Ok(expanded),
            }
        }
    }

    // https://github.com/dtolnay/paste/issues/26
    fn is_none_delimited_flat_group(delimiter: Delimiter, input: &TokenStream) -> bool {
        if delimiter != Delimiter::None {
            return false;
        }

        #[derive(PartialEq)]
        enum State {
            Init,
            Ident,
            Literal,
            Apostrophe,
            Lifetime,
            Colon1,
            Colon2,
        }

        let mut state = State::Init;
        for tt in input.clone() {
            state = match (state, &tt) {
                (State::Init, TokenTree::Ident(_)) => State::Ident,
                (State::Init, TokenTree::Literal(_)) => State::Literal,
                (State::Init, TokenTree::Punct(punct)) if punct.as_char() == '\'' => State::Apostrophe,
                (State::Apostrophe, TokenTree::Ident(_)) => State::Lifetime,
                (State::Ident, TokenTree::Punct(punct))
                    if punct.as_char() == ':' && punct.spacing() == Spacing::Joint =>
                {
                    State::Colon1
                }
                (State::Colon1, TokenTree::Punct(punct))
                    if punct.as_char() == ':' && punct.spacing() == Spacing::Alone =>
                {
                    State::Colon2
                }
                (State::Colon2, TokenTree::Ident(_)) => State::Ident,
                _ => return false,
            };
        }

        state == State::Ident || state == State::Literal || state == State::Lifetime
    }

    struct LitStr {
        value: String,
        span: Span,
    }

    struct Colon {
        span: Span,
    }

    enum Segment {
        String(String),
        Apostrophe(Span),
        Env(LitStr),
        Modifier(Colon, Ident),
    }

    fn is_paste_operation(input: &TokenStream) -> bool {
        let mut tokens = input.clone().into_iter();

        match &tokens.next() {
            Some(TokenTree::Punct(punct)) if punct.as_char() == '<' => {}
            _ => return false,
        }

        let mut has_token = false;
        loop {
            match &tokens.next() {
                Some(TokenTree::Punct(punct)) if punct.as_char() == '>' => {
                    return has_token && tokens.next().is_none();
                }
                Some(_) => has_token = true,
                None => return false,
            }
        }
    }

    fn parse_bracket_as_segments(input: TokenStream, scope: Span) -> Result<Vec<Segment>> {
        let mut tokens = input.into_iter().peekable();

        match &tokens.next() {
            Some(TokenTree::Punct(punct)) if punct.as_char() == '<' => {}
            Some(wrong) => return Err(Error::new(wrong.span(), "expected `<`")),
            None => return Err(Error::new(scope, "expected `[< ... >]`")),
        }

        let segments = parse_segments(&mut tokens, scope)?;

        match &tokens.next() {
            Some(TokenTree::Punct(punct)) if punct.as_char() == '>' => {}
            Some(wrong) => return Err(Error::new(wrong.span(), "expected `>`")),
            None => return Err(Error::new(scope, "expected `[< ... >]`")),
        }

        match tokens.next() {
            Some(unexpected) => Err(Error::new(
                unexpected.span(),
                "unexpected input, expected `[< ... >]`",
            )),
            None => Ok(segments),
        }
    }

    fn parse_segments(
        tokens: &mut Peekable<token_stream::IntoIter>,
        scope: Span,
    ) -> Result<Vec<Segment>> {
        let mut segments = Vec::new();
        while match tokens.peek() {
            None => false,
            Some(TokenTree::Punct(punct)) => punct.as_char() != '>',
            Some(_) => true,
        } {
            match tokens.next().unwrap() {
                TokenTree::Ident(ident) => {
                    let mut fragment = ident.to_string();
                    if fragment.starts_with("r#") {
                        fragment = fragment.split_off(2);
                    }
                    if fragment == "env"
                        && match tokens.peek() {
                            Some(TokenTree::Punct(punct)) => punct.as_char() == '!',
                            _ => false,
                        }
                    {
                        tokens.next().unwrap(); // `!`
                        let expect_group = tokens.next();
                        let parenthesized = match &expect_group {
                            Some(TokenTree::Group(group))
                                if group.delimiter() == Delimiter::Parenthesis =>
                            {
                                group
                            }
                            Some(wrong) => return Err(Error::new(wrong.span(), "expected `(`")),
                            None => return Err(Error::new(scope, "expected `(` after `env!`")),
                        };
                        let mut inner = parenthesized.stream().into_iter();
                        let lit = match inner.next() {
                            Some(TokenTree::Literal(lit)) => lit,
                            Some(wrong) => {
                                return Err(Error::new(wrong.span(), "expected string literal"))
                            }
                            None => {
                                return Err(Error::new2(
                                    ident.span(),
                                    parenthesized.span(),
                                    "expected string literal as argument to env! macro",
                                ))
                            }
                        };
                        let lit_string = lit.to_string();
                        if lit_string.starts_with('"')
                            && lit_string.ends_with('"')
                            && lit_string.len() >= 2
                        {
                            // TODO: maybe handle escape sequences in the string if
                            // someone has a use case.
                            segments.push(Segment::Env(LitStr {
                                value: lit_string[1..lit_string.len() - 1].to_owned(),
                                span: lit.span(),
                            }));
                        } else {
                            return Err(Error::new(lit.span(), "expected string literal"));
                        }
                        if let Some(unexpected) = inner.next() {
                            return Err(Error::new(
                                unexpected.span(),
                                "unexpected token in env! macro",
                            ));
                        }
                    } else {
                        segments.push(Segment::String(fragment));
                    }
                }
                TokenTree::Literal(lit) => {
                    let mut lit_string = lit.to_string();
                    if lit_string.contains(&['#', '\\', '.', '+'][..]) {
                        return Err(Error::new(lit.span(), "unsupported literal"));
                    }
                    lit_string = lit_string
                        .replace('"', "")
                        .replace('\'', "")
                        .replace('-', "_");
                    segments.push(Segment::String(lit_string));
                }
                TokenTree::Punct(punct) => match punct.as_char() {
                    '_' => segments.push(Segment::String("_".to_owned())),
                    '\'' => segments.push(Segment::Apostrophe(punct.span())),
                    ':' => {
                        let colon = Colon { span: punct.span() };
                        let ident = match tokens.next() {
                            Some(TokenTree::Ident(ident)) => ident,
                            wrong => {
                                let span = wrong.as_ref().map_or(scope, TokenTree::span);
                                return Err(Error::new(span, "expected identifier after `:`"));
                            }
                        };
                        segments.push(Segment::Modifier(colon, ident));
                    }
                    _ => return Err(Error::new(punct.span(), "unexpected punct")),
                },
                TokenTree::Group(group) => {
                    if group.delimiter() == Delimiter::None {
                        let mut inner = group.stream().into_iter().peekable();
                        let nested = parse_segments(&mut inner, group.span())?;
                        if let Some(unexpected) = inner.next() {
                            return Err(Error::new(unexpected.span(), "unexpected token"));
                        }
                        segments.extend(nested);
                    } else {
                        return Err(Error::new(group.span(), "unexpected token"));
                    }
                }
            }
        }
        Ok(segments)
    }

    fn paste_segments(span: Span, segments: &[Segment]) -> Result<TokenStream> {
        let mut evaluated = Vec::new();
        let mut is_lifetime = false;

        for segment in segments {
            match segment {
                Segment::String(segment) => {
                    evaluated.push(segment.clone());
                }
                Segment::Apostrophe(span) => {
                    if is_lifetime {
                        return Err(Error::new(*span, "unexpected lifetime"));
                    }
                    is_lifetime = true;
                }
                Segment::Env(var) => {
                    let resolved = match std::env::var(&var.value) {
                        Ok(resolved) => resolved,
                        Err(_) => {
                            return Err(Error::new(
                                var.span,
                                &format!("no such env var: {:?}", var.value),
                            ));
                        }
                    };
                    let resolved = resolved.replace('-', "_");
                    evaluated.push(resolved);
                }
                Segment::Modifier(colon, ident) => {
                    let last = match evaluated.pop() {
                        Some(last) => last,
                        None => {
                            return Err(Error::new2(colon.span, ident.span(), "unexpected modifier"))
                        }
                    };
                    match ident.to_string().as_str() {
                        "lower" => {
                            evaluated.push(last.to_lowercase());
                        }
                        "upper" => {
                            evaluated.push(last.to_uppercase());
                        }
                        "snake" => {
                            let mut acc = String::new();
                            let mut prev = '_';
                            for ch in last.chars() {
                                if ch.is_uppercase() && prev != '_' {
                                    acc.push('_');
                                }
                                acc.push(ch);
                                prev = ch;
                            }
                            evaluated.push(acc.to_lowercase());
                        }
                        "camel" => {
                            let mut acc = String::new();
                            let mut prev = '_';
                            for ch in last.chars() {
                                if ch != '_' {
                                    if prev == '_' {
                                        for chu in ch.to_uppercase() {
                                            acc.push(chu);
                                        }
                                    } else if prev.is_uppercase() {
                                        for chl in ch.to_lowercase() {
                                            acc.push(chl);
                                        }
                                    } else {
                                        acc.push(ch);
                                    }
                                }
                                prev = ch;
                            }
                            evaluated.push(acc);
                        }
                        _ => {
                            return Err(Error::new2(
                                colon.span,
                                ident.span(),
                                "unsupported modifier",
                            ));
                        }
                    }
                }
            }
        }

        let pasted = evaluated.into_iter().collect::<String>();
        let ident = match panic::catch_unwind(|| Ident::new(&pasted, span)) {
            Ok(ident) => TokenTree::Ident(ident),
            Err(_) => {
                return Err(Error::new(
                    span,
                    &format!("`{:?}` is not a valid identifier", pasted),
                ));
            }
        };
        let tokens = if is_lifetime {
            let apostrophe = TokenTree::Punct(Punct::new('\'', Spacing::Joint));
            vec![apostrophe, ident]
        } else {
            vec![ident]
        };
        Ok(TokenStream::from_iter(tokens))
    }