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Be more DRY with conditional cfgs in build.rs

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This commit is contained in:
Jethro Beekman 2019-04-30 18:41:09 -07:00
parent 83eeab3405
commit 29b012608c
1 changed files with 23 additions and 12 deletions
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31
build.rs
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@ -45,6 +45,18 @@ fn parse_mappings(mut mappings: &'static str) -> Vec<Mapping> {
result
}
type Cfg = Option<&'static str>;
type Date = &'static str;
/// A `ConditionalCfg` is basically a list of optional feature names
/// (`Cfg`s) separated by `Date`s. The dates specify ranges of compiler
/// versions for which to enable particular features.
type ConditionalCfg = (Cfg, &'static [(Date, Cfg)]);
const CONDITIONAL_CFGS: &'static [ConditionalCfg] = &[
(None, &[("2018-01-01", Some("core_memchr"))]),
(None, &[("2017-06-15", Some("no_collections"))]),
(Some("rustc_unicode"), &[("2016-12-15", Some("std_unicode")), ("2017-03-03", None)]),
];
fn main() {
let ver=rustc_version::version_meta();
@ -59,18 +71,17 @@ fn main() {
}
};
if ver.commit_date.as_ref().map_or(false,|d| &**d>="2018-01-01") {
println!("cargo:rustc-cfg=core_memchr");
for &(mut curcfg, rest) in CONDITIONAL_CFGS {
for &(date, nextcfg) in rest {
// if no commit_date is provided, assume compiler is current
if ver.commit_date.as_ref().map_or(false,|d| &**d<date) {
break;
}
if ver.commit_date.as_ref().map_or(false,|d| &**d>="2017-06-15") {
println!("cargo:rustc-cfg=no_collections");
curcfg = nextcfg;
}
if let Some(cfg) = curcfg {
println!("cargo:rustc-cfg={}", cfg);
}
if ver.commit_date.as_ref().map_or(false,|d| &**d<"2016-12-15") {
println!("cargo:rustc-cfg=rustc_unicode");
} else if ver.commit_date.as_ref().map_or(false,|d| &**d<"2017-03-03") {
println!("cargo:rustc-cfg=std_unicode");
}
let mut dest_path=PathBuf::from(env::var_os("OUT_DIR").unwrap());