Add requirements to cargo_test.

crates/cargo-test-macro/src/lib.rs

@@ -1,19 +1,62 @@
 extern crate proc_macro;
 
 use proc_macro::*;
+use std::env;
+use std::process::Command;
+use std::sync::Once;
 
 #[proc_macro_attribute]
 pub fn cargo_test(attr: TokenStream, item: TokenStream) -> TokenStream {
+    let mut build_std = false;
+    let mut ignore = false;
+    let mut requires_reason = false;
+    let mut found_reason = false;
+    for rule in split_rules(attr) {
+        match rule.as_str() {
+            "build_std" => build_std = true,
+            "nightly" => {
+                requires_reason = true;
+                ignore |= !version().1;
+            }
+            "disable_git_cli" => {
+                ignore |= disable_git_cli();
+            }
+            s if s.starts_with("requires_") => {
+                let command = &s[9..];
+                ignore |= !has_command(command);
+            }
+            s if s.starts_with(">=1.") => {
+                requires_reason = true;
+                let min_minor = s[4..].parse().unwrap();
+                ignore |= version().0 < min_minor;
+            }
+            s if s.starts_with("reason=") => {
+                found_reason = true;
+            }
+            _ => panic!("unknown rule {:?}", rule),
+        }
+    }
+    if requires_reason && !found_reason {
+        panic!(
+            "#[cargo_test] with a rule also requires a reason, \
+            such as #[cargo_test(nightly, reason = \"needs -Z unstable-thing\")]"
+        );
+    }
+
     let span = Span::call_site();
     let mut ret = TokenStream::new();
-    ret.extend(Some(TokenTree::from(Punct::new('#', Spacing::Alone))));
-    let test = TokenTree::from(Ident::new("test", span));
-    ret.extend(Some(TokenTree::from(Group::new(
-        Delimiter::Bracket,
-        test.into(),
-    ))));
-
-    let build_std = contains_ident(&attr, "build_std");
+    let add_attr = |ret: &mut TokenStream, attr_name| {
+        ret.extend(Some(TokenTree::from(Punct::new('#', Spacing::Alone))));
+        let attr = TokenTree::from(Ident::new(attr_name, span));
+        ret.extend(Some(TokenTree::from(Group::new(
+            Delimiter::Bracket,
+            attr.into(),
+        ))));
+    };
+    add_attr(&mut ret, "test");
+    if ignore {
+        add_attr(&mut ret, "ignore");
+    }
 
     for token in item {
         let group = match token {
@@ -59,13 +102,80 @@ pub fn cargo_test(attr: TokenStream, item: TokenStream) -> TokenStream {
     ret
 }
 
-fn contains_ident(t: &TokenStream, ident: &str) -> bool {
-    t.clone().into_iter().any(|t| match t {
-        TokenTree::Ident(i) => i.to_string() == ident,
+fn split_rules(t: TokenStream) -> Vec<String> {
+    let tts: Vec<_> = t.into_iter().collect();
+    tts.split(|tt| match tt {
+        TokenTree::Punct(p) => p.as_char() == ',',
         _ => false,
     })
+    .filter(|parts| !parts.is_empty())
+    .map(|parts| {
+        parts
+            .into_iter()
+            .map(|part| part.to_string())
+            .collect::<String>()
+    })
+    .collect()
 }
 
 fn to_token_stream(code: &str) -> TokenStream {
     code.parse().unwrap()
 }
+
+static mut VERSION: (u32, bool) = (0, false);
+
+fn version() -> &'static (u32, bool) {
+    static INIT: Once = Once::new();
+    INIT.call_once(|| {
+        let output = Command::new("rustc")
+            .arg("-V")
+            .output()
+            .expect("rustc should run");
+        let stdout = std::str::from_utf8(&output.stdout).expect("utf8");
+        let vers = stdout.split_whitespace().skip(1).next().unwrap();
+        let is_nightly = env::var("CARGO_TEST_DISABLE_NIGHTLY").is_err()
+            && (vers.contains("-nightly") || vers.contains("-dev"));
+        let minor = vers.split('.').skip(1).next().unwrap().parse().unwrap();
+        unsafe { VERSION = (minor, is_nightly) }
+    });
+    unsafe { &VERSION }
+}
+
+fn disable_git_cli() -> bool {
+    // mingw git on Windows does not support Windows-style file URIs.
+    // Appveyor in the rust repo has that git up front in the PATH instead
+    // of Git-for-Windows, which causes this to fail.
+    env::var("CARGO_TEST_DISABLE_GIT_CLI") == Ok("1".to_string())
+}
+
+fn has_command(command: &str) -> bool {
+    let output = match Command::new(command).arg("--version").output() {
+        Ok(output) => output,
+        Err(e) => {
+            if is_ci() {
+                panic!(
+                    "expected command `{}` to be somewhere in PATH: {}",
+                    command, e
+                );
+            }
+            return false;
+        }
+    };
+    if !output.status.success() {
+        panic!(
+            "expected command `{}` to be runnable, got error {}:\n\
+            stderr:{}\n\
+            stdout:{}\n",
+            command,
+            output.status,
+            String::from_utf8_lossy(&output.stderr),
+            String::from_utf8_lossy(&output.stdout)
+        );
+    }
+    true
+}
+
+/// Whether or not this running in a Continuous Integration environment.
+fn is_ci() -> bool {
+    std::env::var("CI").is_ok() || std::env::var("TF_BUILD").is_ok()
+}

crates/cargo-test-support/src/lib.rs

@@ -1128,6 +1128,10 @@ pub fn rustc_host_env() -> String {
 
 pub fn is_nightly() -> bool {
     let vv = &RUSTC_INFO.verbose_version;
+    // CARGO_TEST_DISABLE_NIGHTLY is set in rust-lang/rust's CI so that all
+    // nightly-only tests are disabled there. Otherwise, it could make it
+    // difficult to land changes which would need to be made simultaneously in
+    // rust-lang/cargo and rust-lan/rust, which isn't possible.
     env::var("CARGO_TEST_DISABLE_NIGHTLY").is_err()
         && (vv.contains("-nightly") || vv.contains("-dev"))
 }
@@ -1350,16 +1354,6 @@ pub fn slow_cpu_multiplier(main: u64) -> Duration {
     Duration::from_secs(*SLOW_CPU_MULTIPLIER * main)
 }
 
-pub fn command_is_available(cmd: &str) -> bool {
-    if let Err(e) = process(cmd).arg("-V").exec_with_output() {
-        eprintln!("{} not available, skipping tests", cmd);
-        eprintln!("{:?}", e);
-        false
-    } else {
-        true
-    }
-}
-
 #[cfg(windows)]
 pub fn symlink_supported() -> bool {
     if is_ci() {

src/doc/contrib/src/tests/writing.md

@@ -50,13 +50,7 @@ fn <description>() {
 }
 ```
 
-`#[cargo_test]`:
-- This is used in place of `#[test]`
-- This attribute injects code which does some setup before starting the
-  test, creating a filesystem "sandbox" under the "cargo integration test"
-  directory for each test such as
-  `/path/to/cargo/target/cit/t123/`
-- The sandbox will contain a `home` directory that will be used instead of your normal home directory
+The [`#[cargo_test]` attribute](#cargo_test-attribute) is used in place of `#[test]` to inject some setup code.
 
 [`ProjectBuilder`] via `project()`:
 - Each project is in a separate directory in the sandbox
@@ -68,6 +62,37 @@ fn <description>() {
   - See [`support::compare`] for an explanation of the string pattern matching.
     Patterns are used to make it easier to match against the expected output.
 
+#### `#[cargo_test]` attribute
+
+The `#[cargo_test]` attribute injects code which does some setup before starting the test.
+It will create a filesystem "sandbox" under the "cargo integration test" directory for each test, such as `/path/to/cargo/target/tmp/cit/t123/`.
+The sandbox will contain a `home` directory that will be used instead of your normal home directory.
+
+The `#[cargo_test`] attribute takes several options that will affect how the test is generated.
+They are listed in parentheses separated with commas, such as:
+
+```rust,ignore
+#[cargo_test(nightly, reason = "-Zfoo is unstable")]
+```
+
+The options it supports are:
+
+* `nightly` — This will cause the test to be ignored if not running on the nightly toolchain.
+  This is useful for tests that use unstable options in `rustc` or `rustdoc`.
+  These tests are run in Cargo's CI, but are disabled in rust-lang/rust's CI due to the difficulty of updating both repos simultaneously.
+  A `reason` field is required to explain why it is nightly-only.
+* `build_std` — This is a `-Zbuild-std` test.
+  This only runs on nightly, and only if the environment variable `CARGO_RUN_BUILD_STD_TESTS` is set.
+* `requires_` — This indicates a command that is required to be installed to be run.
+  For example, `requires_rustmft` means the test will only run if the executable `rustfmt` is installed.
+  These tests are *always* run on CI.
+  This is mainly used to avoid requiring contributors from having every dependency installed.
+* `>=1.64` — This indicates that the test will only run with the given version of `rustc` or newer.
+  This can be used when a new `rustc` feature has been stabilized that the test depends on.
+  If this is specified, a `reason` is required to explain why it is being checked.
+* `disable_git_cli` — This is needed for `git-fetch-with-cli` tests.
+  This disables the test in rust-lang/rust's CI due to a compatibility issue.
+
 #### Testing Nightly Features
 
 If you are testing a Cargo feature that only works on "nightly" Cargo, then
@@ -79,16 +104,15 @@ p.cargo("build").masquerade_as_nightly_cargo(&["print-im-a-teapot"])
 ```
 
 If you are testing a feature that only works on *nightly rustc* (such as
-benchmarks), then you should exit the test if it is not running with nightly
-rust, like this:
+benchmarks), then you should use the `nightly` option of the `cargo_test`
+attribute, like this:
 
 ```rust,ignore
-if !is_nightly() {
-    // Add a comment here explaining why this is necessary.
-    return;
-}
+#[cargo_test(nightly, reason = "-Zfoo is unstable")]
 ```
 
+This will cause the test to be ignored if not running on the nightly toolchain.
+
 #### Specifying Dependencies
 
 You should not write any tests that use the network such as contacting
@@ -201,16 +225,15 @@ the name of the feature as the reason, like this:
 ```
 
 If you are testing a feature that only works on *nightly rustc* (such as
-benchmarks), then you should exit the test if it is not running with nightly
-rust, like this:
+benchmarks), then you should use the `nightly` option of the `cargo_test`
+attribute, like this:
 
 ```rust,ignore
-if !is_nightly() {
-    // Add a comment here explaining why this is necessary.
-    return;
-}
+#[cargo_test(nightly, reason = "-Zfoo is unstable")]
 ```
 
+This will cause the test to be ignored if not running on the nightly toolchain.
+
 ### Platform-specific Notes
 
 When checking output, use `/` for paths even on Windows: the actual output