rust/src/libsyntax/attr.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Functions dealing with attributes and meta items

use extra;

use ast;
use ast::{Attribute, Attribute_, MetaItem, MetaWord, MetaNameValue, MetaList};
use codemap::{spanned, dummy_spanned};
use codemap::BytePos;
use diagnostic::span_handler;
use parse::comments::{doc_comment_style, strip_doc_comment_decoration};

use std::hashmap::HashSet;

pub trait AttrMetaMethods {
    // This could be changed to `fn check_name(&self, name: @str) ->
    // bool` which would facilitate a side table recording which
    // attributes/meta items are used/unused.

    /// Retrieve the name of the meta item, e.g. foo in #[foo],
    /// #[foo="bar"] and #[foo(bar)]
    fn name(&self) -> @str;

    /**
     * Gets the string value if self is a MetaNameValue variant
     * containing a string, otherwise None.
     */
    fn value_str(&self) -> Option<@str>;
    /// Gets a list of inner meta items from a list MetaItem type.
    fn meta_item_list<'a>(&'a self) -> Option<&'a [@MetaItem]>;

    /**
     * If the meta item is a name-value type with a string value then returns
     * a tuple containing the name and string value, otherwise `None`
     */
    fn name_str_pair(&self) -> Option<(@str, @str)>;
}

impl AttrMetaMethods for Attribute {
    fn name(&self) -> @str { self.meta().name() }
    fn value_str(&self) -> Option<@str> { self.meta().value_str() }
    fn meta_item_list<'a>(&'a self) -> Option<&'a [@MetaItem]> {
        self.node.value.meta_item_list()
    }
    fn name_str_pair(&self) -> Option<(@str, @str)> { self.meta().name_str_pair() }
}

impl AttrMetaMethods for MetaItem {
    fn name(&self) -> @str {
        match self.node {
            MetaWord(n) => n,
            MetaNameValue(n, _) => n,
            MetaList(n, _) => n
        }
    }

    fn value_str(&self) -> Option<@str> {
        match self.node {
            MetaNameValue(_, ref v) => {
                match v.node {
                    ast::lit_str(s) => Some(s),
                    _ => None,
                }
            },
            _ => None
        }
    }

    fn meta_item_list<'a>(&'a self) -> Option<&'a [@MetaItem]> {
        match self.node {
            MetaList(_, ref l) => Some(l.as_slice()),
            _ => None
        }
    }

    pub fn name_str_pair(&self) -> Option<(@str, @str)> {
        self.value_str().map_consume(|s| (self.name(), s))
    }
}

// Annoying, but required to get test_cfg to work
impl AttrMetaMethods for @MetaItem {
    fn name(&self) -> @str { (**self).name() }
    fn value_str(&self) -> Option<@str> { (**self).value_str() }
    fn meta_item_list<'a>(&'a self) -> Option<&'a [@MetaItem]> {
        (**self).meta_item_list()
    }
    fn name_str_pair(&self) -> Option<(@str, @str)> { (**self).name_str_pair() }
}


pub trait AttributeMethods {
    fn meta(&self) -> @MetaItem;
    fn desugar_doc(&self) -> Attribute;
}

impl AttributeMethods for Attribute {
    /// Extract the MetaItem from inside this Attribute.
    pub fn meta(&self) -> @MetaItem {
        self.node.value
    }

    /// Convert self to a normal #[doc="foo"] comment, if it is a
    /// comment like `///` or `/** */`. (Returns self unchanged for
    /// non-sugared doc attributes.)
    pub fn desugar_doc(&self) -> Attribute {
        if self.node.is_sugared_doc {
            let comment = self.value_str().get();
            let meta = mk_name_value_item_str(@"doc",
                                              strip_doc_comment_decoration(comment).to_managed());
            mk_attr(meta)
        } else {
            *self
        }
    }
}

/* Constructors */

pub fn mk_name_value_item_str(name: @str, value: @str) -> @MetaItem {
    let value_lit = dummy_spanned(ast::lit_str(value));
    mk_name_value_item(name, value_lit)
}

pub fn mk_name_value_item(name: @str, value: ast::lit) -> @MetaItem {
    @dummy_spanned(MetaNameValue(name, value))
}

pub fn mk_list_item(name: @str, items: ~[@MetaItem]) -> @MetaItem {
    @dummy_spanned(MetaList(name, items))
}

pub fn mk_word_item(name: @str) -> @MetaItem {
    @dummy_spanned(MetaWord(name))
}

pub fn mk_attr(item: @MetaItem) -> Attribute {
    dummy_spanned(Attribute_ {
        style: ast::AttrInner,
        value: item,
        is_sugared_doc: false,
    })
}

pub fn mk_sugared_doc_attr(text: @str, lo: BytePos, hi: BytePos) -> Attribute {
    let style = doc_comment_style(text);
    let lit = spanned(lo, hi, ast::lit_str(text));
    let attr = Attribute_ {
        style: style,
        value: @spanned(lo, hi, MetaNameValue(@"doc", lit)),
        is_sugared_doc: true
    };
    spanned(lo, hi, attr)
}

/* Searching */
/// Check if `needle` occurs in `haystack` by a structural
/// comparison. This is slightly subtle, and relies on ignoring the
/// span included in the `==` comparison a plain MetaItem.
pub fn contains(haystack: &[@ast::MetaItem],
                needle: @ast::MetaItem) -> bool {
    debug!("attr::contains (name=%s)", needle.name());
    do haystack.iter().any |item| {
        debug!("  testing: %s", item.name());
        item.node == needle.node
    }
}

pub fn contains_name<AM: AttrMetaMethods>(metas: &[AM], name: &str) -> bool {
    debug!("attr::contains_name (name=%s)", name);
    do metas.iter().any |item| {
        debug!("  testing: %s", item.name());
        name == item.name()
    }
}

pub fn first_attr_value_str_by_name(attrs: &[Attribute], name: &str)
                                 -> Option<@str> {
    attrs.iter()
        .find_(|at| name == at.name())
        .chain(|at| at.value_str())
}

pub fn last_meta_item_value_str_by_name(items: &[@MetaItem], name: &str)
                                     -> Option<@str> {
    items.rev_iter().find_(|mi| name == mi.name()).chain(|i| i.value_str())
}

/* Higher-level applications */

pub fn sort_meta_items(items: &[@MetaItem]) -> ~[@MetaItem] {
    // This is sort of stupid here, but we need to sort by
    // human-readable strings.
    let mut v = items.iter()
        .transform(|&mi| (mi.name(), mi))
        .collect::<~[(@str, @MetaItem)]>();

    do extra::sort::quick_sort(v) |&(a, _), &(b, _)| {
        a <= b
    }

    // There doesn't seem to be a more optimal way to do this
    do v.consume_iter().transform |(_, m)| {
        match m.node {
            MetaList(n, ref mis) => {
                @spanned {
                    node: MetaList(n, sort_meta_items(*mis)),
                    .. /*bad*/ (*m).clone()
                }
            }
            _ => m
        }
    }.collect()
}

/**
 * From a list of crate attributes get only the meta_items that affect crate
 * linkage
 */
pub fn find_linkage_metas(attrs: &[Attribute]) -> ~[@MetaItem] {
    let mut result = ~[];
    for attr in attrs.iter().filter(|at| "link" == at.name()) {
        match attr.meta().node {
            MetaList(_, ref items) => result.push_all(*items),
            _ => ()
        }
    }
    result
}

#[deriving(Eq)]
pub enum InlineAttr {
    InlineNone,
    InlineHint,
    InlineAlways,
    InlineNever,
}

/// True if something like #[inline] is found in the list of attrs.
pub fn find_inline_attr(attrs: &[Attribute]) -> InlineAttr {
    // FIXME (#2809)---validate the usage of #[inline] and #[inline]
    do attrs.iter().fold(InlineNone) |ia,attr| {
        match attr.node.value.node {
          MetaWord(n) if "inline" == n => InlineHint,
          MetaList(n, ref items) if "inline" == n => {
            if contains_name(*items, "always") {
                InlineAlways
            } else if contains_name(*items, "never") {
                InlineNever
            } else {
                InlineHint
            }
          }
          _ => ia
        }
    }
}

/// Tests if any `cfg(...)` meta items in `metas` match `cfg`. e.g.
///
/// test_cfg(`[foo="a", bar]`, `[cfg(foo), cfg(bar)]`) == true
/// test_cfg(`[foo="a", bar]`, `[cfg(not(bar))]`) == false
/// test_cfg(`[foo="a", bar]`, `[cfg(bar, foo="a")]`) == true
/// test_cfg(`[foo="a", bar]`, `[cfg(bar, foo="b")]`) == false
pub fn test_cfg<AM: AttrMetaMethods, It: Iterator<AM>>
    (cfg: &[@MetaItem], mut metas: It) -> bool {
    // having no #[cfg(...)] attributes counts as matching.
    let mut no_cfgs = true;

    // this would be much nicer as a chain of iterator adaptors, but
    // this doesn't work.
    let some_cfg_matches = do metas.any |mi| {
        debug!("testing name: %s", mi.name());
        if "cfg" == mi.name() { // it is a #[cfg()] attribute
            debug!("is cfg");
            no_cfgs = false;
             // only #[cfg(...)] ones are understood.
            match mi.meta_item_list() {
                Some(cfg_meta) => {
                    debug!("is cfg(...)");
                    do cfg_meta.iter().all |cfg_mi| {
                        debug!("cfg(%s[...])", cfg_mi.name());
                        match cfg_mi.node {
                            ast::MetaList(s, ref not_cfgs) if "not" == s => {
                                debug!("not!");
                                // inside #[cfg(not(...))], so these need to all
                                // not match.
                                not_cfgs.iter().all(|mi| {
                                    debug!("cfg(not(%s[...]))", mi.name());
                                    !contains(cfg, *mi)
                                })
                            }
                            _ => contains(cfg, *cfg_mi)
                        }
                    }
                }
                None => false
            }
        } else {
            false
        }
    };
    debug!("test_cfg (no_cfgs=%?, some_cfg_matches=%?)", no_cfgs, some_cfg_matches);
    no_cfgs || some_cfg_matches
}

pub fn require_unique_names(diagnostic: @span_handler,
                            metas: &[@MetaItem]) {
    let mut set = HashSet::new();
    for meta in metas.iter() {
        let name = meta.name();

        // FIXME: How do I silence the warnings? --pcw (#2619)
        if !set.insert(name) {
            diagnostic.span_fatal(meta.span,
                                  fmt!("duplicate meta item `%s`", name));
        }
    }
}