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alexcrichtonalexcrichton
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Implement cfg-based target-specific dependencies
This commit is an implementation of [RFC 1361][rfc] which is an extension of Cargo's `target` section in `Cargo.toml` to allow the use of `#[cfg]`-like expressions for target-specific dependencies. Now that the compiler has been extended with `--print cfg` each invocation of Cargo will scrape this output and learn about the relevant `#[cfg]` directives in play for the target being compiled. Cargo will then use these directives to decide whether a dependency should be activated or not. This should allow definition of dependencies along the lines of: [target.'cfg(unix)'.dependencies] [target.'cfg(target_os = "linux")'.dependencies] [target.'cfg(windows)'.dependencies] Which is much more ergonomic and robust than listing all the triples out!
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-116
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11 files changed

+823
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lines changed

‎src/cargo/core/dependency.rs

+74-22
Original file line numberDiff line numberDiff line change
@@ -1,12 +1,22 @@
1+
use std::fmt;
2+
use std::rc::Rc;
3+
use std::str::FromStr;
4+
15
use semver::VersionReq;
26
use rustc_serialize::{Encoder, Encodable};
37

48
use core::{SourceId, Summary, PackageId};
5-
use std::rc::Rc;
6-
use util::CargoResult;
9+
use util::{CargoError, CargoResult, Cfg, CfgExpr, ChainError, human};
10+
11+
/// Information about a dependency requested by a Cargo manifest.
12+
/// Cheap to copy.
13+
#[derive(PartialEq, Clone ,Debug)]
14+
pub struct Dependency {
15+
inner: Rc<DependencyInner>,
16+
}
717

818
/// The data underlying a Dependency.
9-
#[derive(PartialEq,Clone,Debug)]
19+
#[derive(PartialEq, Clone, Debug)]
1020
pub struct DependencyInner {
1121
name: String,
1222
source_id: SourceId,
@@ -21,17 +31,15 @@ pub struct DependencyInner {
2131

2232
// This dependency should be used only for this platform.
2333
// `None` means *all platforms*.
24-
only_for_platform: Option<String>,
34+
platform: Option<Platform>,
2535
}
2636

27-
/// Information about a dependency requested by a Cargo manifest.
28-
/// Cheap to copy.
29-
#[derive(PartialEq,Clone,Debug)]
30-
pub struct Dependency {
31-
inner: Rc<DependencyInner>,
37+
#[derive(Clone, Debug, PartialEq)]
38+
pub enum Platform {
39+
Name(String),
40+
Cfg(CfgExpr),
3241
}
3342

34-
3543
#[derive(RustcEncodable)]
3644
struct SerializedDependency<'a> {
3745
name: &'a str,
@@ -42,7 +50,7 @@ struct SerializedDependency<'a> {
4250
optional: bool,
4351
uses_default_features: bool,
4452
features: &'a [String],
45-
target: &'a Option<&'a str>,
53+
target: Option<&'a Platform>,
4654
}
4755

4856
impl Encodable for Dependency {
@@ -55,7 +63,7 @@ impl Encodable for Dependency {
5563
optional: self.is_optional(),
5664
uses_default_features: self.uses_default_features(),
5765
features: self.features(),
58-
target: &self.only_for_platform(),
66+
target: self.platform(),
5967
}.encode(s)
6068
}
6169
}
@@ -106,7 +114,7 @@ impl DependencyInner {
106114
features: Vec::new(),
107115
default_features: true,
108116
specified_req: None,
109-
only_for_platform: None,
117+
platform: None,
110118
}
111119
}
112120

@@ -118,10 +126,10 @@ impl DependencyInner {
118126
self.specified_req.as_ref().map(|s| &s[..])
119127
}
120128

121-
/// If none, this dependencies must be built for all platforms.
122-
/// If some, it must only be built for the specified platform.
123-
pub fn only_for_platform(&self) -> Option<&str> {
124-
self.only_for_platform.as_ref().map(|s| &s[..])
129+
/// If none, this dependency must be built for all platforms.
130+
/// If some, it must only be built for matching platforms.
131+
pub fn platform(&self) -> Option<&Platform> {
132+
self.platform.as_ref()
125133
}
126134

127135
pub fn set_kind(mut self, kind: Kind) -> DependencyInner {
@@ -159,9 +167,9 @@ impl DependencyInner {
159167
self
160168
}
161169

162-
pub fn set_only_for_platform(mut self, platform: Option<String>)
163-
-> DependencyInner {
164-
self.only_for_platform = platform;
170+
pub fn set_platform(mut self, platform: Option<Platform>)
171+
-> DependencyInner {
172+
self.platform = platform;
165173
self
166174
}
167175

@@ -230,8 +238,8 @@ impl Dependency {
230238

231239
/// If none, this dependencies must be built for all platforms.
232240
/// If some, it must only be built for the specified platform.
233-
pub fn only_for_platform(&self) -> Option<&str> {
234-
self.inner.only_for_platform()
241+
pub fn platform(&self) -> Option<&Platform> {
242+
self.inner.platform()
235243
}
236244

237245
/// Lock this dependency to depending on the specified package id
@@ -258,3 +266,47 @@ impl Dependency {
258266
self.inner.matches_id(id)
259267
}
260268
}
269+
270+
impl Platform {
271+
pub fn matches(&self, name: &str, cfg: Option<&[Cfg]>) -> bool {
272+
match *self {
273+
Platform::Name(ref p) => p == name,
274+
Platform::Cfg(ref p) => {
275+
match cfg {
276+
Some(cfg) => p.matches(cfg),
277+
None => false,
278+
}
279+
}
280+
}
281+
}
282+
}
283+
284+
impl Encodable for Platform {
285+
fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
286+
self.to_string().encode(s)
287+
}
288+
}
289+
290+
impl FromStr for Platform {
291+
type Err = Box<CargoError>;
292+
293+
fn from_str(s: &str) -> CargoResult<Platform> {
294+
if s.starts_with("cfg(") && s.ends_with(")") {
295+
let s = &s[4..s.len()-1];
296+
s.parse().map(Platform::Cfg).chain_error(|| {
297+
human(format!("failed to parse `{}` as a cfg expression", s))
298+
})
299+
} else {
300+
Ok(Platform::Name(s.to_string()))
301+
}
302+
}
303+
}
304+
305+
impl fmt::Display for Platform {
306+
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
307+
match *self {
308+
Platform::Name(ref n) => n.fmt(f),
309+
Platform::Cfg(ref e) => write!(f, "cfg({})", e),
310+
}
311+
}
312+
}

‎src/cargo/ops/cargo_rustc/context.rs

+61-39
Original file line numberDiff line numberDiff line change
@@ -1,14 +1,14 @@
11
use std::collections::{HashSet, HashMap};
22
use std::path::{Path, PathBuf};
3-
use std::str;
3+
use std::str::{self, FromStr};
44
use std::sync::Arc;
55

66
use regex::Regex;
77

88
use core::{SourceMap, Package, PackageId, PackageSet, Resolve, Target, Profile};
99
use core::{TargetKind, LibKind, Profiles, Metadata, Dependency};
1010
use core::dependency::Kind as DepKind;
11-
use util::{self, CargoResult, ChainError, internal, Config, profile};
11+
use util::{self, CargoResult, ChainError, internal, Config, profile, Cfg, human};
1212

1313
use super::TargetConfig;
1414
use super::custom_build::{BuildState, BuildScripts};
@@ -41,16 +41,20 @@ pub struct Context<'a, 'cfg: 'a> {
4141
host: Layout,
4242
target: Option<Layout>,
4343
target_triple: String,
44-
host_dylib: Option<(String, String)>,
45-
host_staticlib: Option<(String, String)>,
46-
host_exe: String,
44+
target_info: TargetInfo,
45+
host_info: TargetInfo,
4746
package_set: &'a PackageSet,
48-
target_dylib: Option<(String, String)>,
49-
target_staticlib: Option<(String, String)>,
50-
target_exe: String,
5147
profiles: &'a Profiles,
5248
}
5349

50+
#[derive(Clone)]
51+
struct TargetInfo {
52+
dylib: Option<(String, String)>,
53+
staticlib: Option<(String, String)>,
54+
exe: String,
55+
cfg: Option<Vec<Cfg>>,
56+
}
57+
5458
impl<'a, 'cfg> Context<'a, 'cfg> {
5559
pub fn new(resolve: &'a Resolve,
5660
sources: &'a SourceMap<'cfg>,
@@ -62,12 +66,11 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
6266
profiles: &'a Profiles) -> CargoResult<Context<'a, 'cfg>> {
6367
let target = build_config.requested_target.clone();
6468
let target = target.as_ref().map(|s| &s[..]);
65-
let (target_dylib, target_staticlib, target_exe) = try!(Context::filename_parts(target,
66-
config));
67-
let (host_dylib, host_staticlib, host_exe) = if build_config.requested_target.is_none() {
68-
(target_dylib.clone(), target_staticlib.clone(), target_exe.clone())
69+
let target_info = try!(Context::target_info(target, config));
70+
let host_info = if build_config.requested_target.is_none() {
71+
target_info.clone()
6972
} else {
70-
try!(Context::filename_parts(None, config))
73+
try!(Context::target_info(None, config))
7174
};
7275
let target_triple = target.unwrap_or_else(|| {
7376
&config.rustc_info().host[..]
@@ -83,12 +86,8 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
8386
sources: sources,
8487
package_set: deps,
8588
config: config,
86-
target_dylib: target_dylib,
87-
target_staticlib: target_staticlib,
88-
target_exe: target_exe,
89-
host_dylib: host_dylib,
90-
host_staticlib: host_staticlib,
91-
host_exe: host_exe,
89+
target_info: target_info,
90+
host_info: host_info,
9291
compilation: Compilation::new(config),
9392
build_state: Arc::new(BuildState::new(&build_config, deps)),
9493
build_config: build_config,
@@ -103,8 +102,8 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
103102

104103
/// Run `rustc` to discover the dylib prefix/suffix for the target
105104
/// specified as well as the exe suffix
106-
fn filename_parts(target: Option<&str>, cfg: &Config)
107-
-> CargoResult<(Option<(String, String)>, Option<(String, String)>, String)> {
105+
fn target_info(target: Option<&str>, cfg: &Config)
106+
-> CargoResult<TargetInfo> {
108107
let mut process = util::process(cfg.rustc());
109108
process.arg("-")
110109
.arg("--crate-name").arg("_")
@@ -116,7 +115,18 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
116115
if let Some(s) = target {
117116
process.arg("--target").arg(s);
118117
};
119-
let output = try!(process.exec_with_output());
118+
119+
let mut with_cfg = process.clone();
120+
with_cfg.arg("--print=cfg");
121+
122+
let mut has_cfg = true;
123+
let output = try!(with_cfg.exec_with_output().or_else(|_| {
124+
has_cfg = false;
125+
process.exec_with_output()
126+
}).chain_error(|| {
127+
human(format!("failed to run `rustc` to learn about \
128+
target-specific information"))
129+
}));
120130

121131
let error = str::from_utf8(&output.stderr).unwrap();
122132
let output = str::from_utf8(&output.stdout).unwrap();
@@ -143,13 +153,25 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
143153
Some((staticlib_parts[0].to_string(), staticlib_parts[1].to_string()))
144154
};
145155

146-
let exe_suffix = if nobin.is_match(error) {
156+
let exe = if nobin.is_match(error) {
147157
String::new()
148158
} else {
149159
lines.next().unwrap().trim()
150160
.split('_').skip(1).next().unwrap().to_string()
151161
};
152-
Ok((dylib, staticlib, exe_suffix))
162+
163+
let cfg = if has_cfg {
164+
Some(try!(lines.map(Cfg::from_str).collect()))
165+
} else {
166+
None
167+
};
168+
169+
Ok(TargetInfo {
170+
dylib: dylib,
171+
staticlib: staticlib,
172+
exe: exe,
173+
cfg: cfg,
174+
})
153175
}
154176

155177
/// Prepare this context, ensuring that all filesystem directories are in
@@ -207,9 +229,9 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
207229
/// otherwise it corresponds to the target platform.
208230
fn dylib(&self, kind: Kind) -> CargoResult<(&str, &str)> {
209231
let (triple, pair) = if kind == Kind::Host {
210-
(&self.config.rustc_info().host, &self.host_dylib)
232+
(&self.config.rustc_info().host, &self.host_info.dylib)
211233
} else {
212-
(&self.target_triple, &self.target_dylib)
234+
(&self.target_triple, &self.target_info.dylib)
213235
};
214236
match *pair {
215237
None => bail!("dylib outputs are not supported for {}", triple),
@@ -223,9 +245,9 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
223245
/// otherwise it corresponds to the target platform.
224246
pub fn staticlib(&self, kind: Kind) -> CargoResult<(&str, &str)> {
225247
let (triple, pair) = if kind == Kind::Host {
226-
(&self.config.rustc_info().host, &self.host_staticlib)
248+
(&self.config.rustc_info().host, &self.host_info.staticlib)
227249
} else {
228-
(&self.target_triple, &self.target_staticlib)
250+
(&self.target_triple, &self.target_info.staticlib)
229251
};
230252
match *pair {
231253
None => bail!("staticlib outputs are not supported for {}", triple),
@@ -284,9 +306,9 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
284306
pub fn target_filenames(&self, unit: &Unit) -> CargoResult<Vec<String>> {
285307
let stem = self.file_stem(unit);
286308
let suffix = if unit.target.for_host() {
287-
&self.host_exe
309+
&self.host_info.exe
288310
} else {
289-
&self.target_exe
311+
&self.target_info.exe
290312
};
291313

292314
let mut ret = Vec::new();
@@ -532,15 +554,15 @@ impl<'a, 'cfg> Context<'a, 'cfg> {
532554
fn dep_platform_activated(&self, dep: &Dependency, kind: Kind) -> bool {
533555
// If this dependency is only available for certain platforms,
534556
// make sure we're only enabling it for that platform.
535-
match (dep.only_for_platform(), kind) {
536-
(Some(ref platform), Kind::Host) => {
537-
*platform == self.config.rustc_info().host
538-
},
539-
(Some(ref platform), Kind::Target) => {
540-
*platform == self.target_triple
541-
},
542-
(None, _) => true
543-
}
557+
let platform = match dep.platform() {
558+
Some(p) => p,
559+
None => return true,
560+
};
561+
let (name, info) = match kind {
562+
Kind::Host => (&self.config.rustc_info().host, &self.host_info),
563+
Kind::Target => (&self.target_triple, &self.target_info),
564+
};
565+
platform.matches(name, info.cfg.as_ref().map(|cfg| &cfg[..]))
544566
}
545567

546568
/// Gets a package for the given package id.

‎src/cargo/ops/registry.rs

+1-1
Original file line numberDiff line numberDiff line change
@@ -81,7 +81,7 @@ fn transmit(pkg: &Package, tarball: &Path, registry: &mut Registry)
8181
name: dep.name().to_string(),
8282
features: dep.features().to_vec(),
8383
version_req: dep.version_req().to_string(),
84-
target: dep.only_for_platform().map(|s| s.to_string()),
84+
target: dep.platform().map(|s| s.to_string()),
8585
kind: match dep.kind() {
8686
Kind::Normal => "normal",
8787
Kind::Build => "build",

‎src/cargo/sources/registry.rs

+6-1
Original file line numberDiff line numberDiff line change
@@ -435,6 +435,11 @@ impl<'cfg> RegistrySource<'cfg> {
435435
_ => Kind::Normal,
436436
};
437437

438+
let platform = match target {
439+
Some(target) => Some(try!(target.parse())),
440+
None => None,
441+
};
442+
438443
// Unfortunately older versions of cargo and/or the registry ended up
439444
// publishing lots of entries where the features array contained the
440445
// empty feature, "", inside. This confuses the resolution process much
@@ -445,7 +450,7 @@ impl<'cfg> RegistrySource<'cfg> {
445450
Ok(dep.set_optional(optional)
446451
.set_default_features(default_features)
447452
.set_features(features)
448-
.set_only_for_platform(target)
453+
.set_platform(platform)
449454
.set_kind(kind)
450455
.into_dependency())
451456
}

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