Make --print=check-cfg output compatible --check-cfg arguments

compiler/rustc_driver_impl/src/lib.rs

@@ -765,30 +765,35 @@ fn print_crate_info(
                 for (name, expected_values) in &sess.psess.check_config.expecteds {
                     use crate::config::ExpectedValues;
                     match expected_values {
-                        ExpectedValues::Any => check_cfgs.push(format!("{name}=any()")),
+                        ExpectedValues::Any => {
+                            check_cfgs.push(format!("cfg({name}, values(any()))"))
+                        }
                         ExpectedValues::Some(values) => {
-                            if !values.is_empty() {
-                                check_cfgs.extend(values.iter().map(|value| {
+                            let mut values: Vec<_> = values
+                                .iter()
+                                .map(|value| {
                                     if let Some(value) = value {
-                                        format!("{name}=\"{value}\"")
+                                        format!("\"{value}\"")
                                     } else {
-                                        name.to_string()
+                                        "none()".to_string()
                                     }
-                                }))
-                            } else {
-                                check_cfgs.push(format!("{name}="))
-                            }
+                                })
+                                .collect();
+
+                            values.sort_unstable();
+
+                            let values = values.join(", ");
+
+                            check_cfgs.push(format!("cfg({name}, values({values}))"))
                         }
                     }
                 }
 
                 check_cfgs.sort_unstable();
-                if !sess.psess.check_config.exhaustive_names {
-                    if !sess.psess.check_config.exhaustive_values {
-                        println_info!("any()=any()");
-                    } else {
-                        println_info!("any()");
-                    }
+                if !sess.psess.check_config.exhaustive_names
+                    && sess.psess.check_config.exhaustive_values
+                {
+                    println_info!("cfg(any())");
                 }
                 for check_cfg in check_cfgs {
                     println_info!("{check_cfg}");

src/doc/unstable-book/src/compiler-flags/print-check-cfg.md

@@ -9,23 +9,28 @@ This option of the `--print` flag print the list of all the expected cfgs.
 This is related to the [`--check-cfg` flag][check-cfg] which allows specifying arbitrary expected
 names and values.
 
-This print option works similarly to `--print=cfg` (modulo check-cfg specifics).
-
-| `--check-cfg`                     | `--print=check-cfg`         |
-|-----------------------------------|-----------------------------|
-| `cfg(foo)`                        | `foo`                       |
-| `cfg(foo, values("bar"))`         | `foo="bar"`                 |
-| `cfg(foo, values(none(), "bar"))` | `foo` & `foo="bar"`         |
-|                                   | *check-cfg specific syntax* |
-| `cfg(foo, values(any())`          | `foo=any()`                 |
-| `cfg(foo, values())`              | `foo=`                      |
-| `cfg(any())`                      | `any()`                     |
-| *none*                            | `any()=any()`               |
+This print option outputs compatible `--check-cfg` arguments with a reduced syntax where all the
+expected values are on the same line and `values(...)` is always explicit.
+
+| `--check-cfg`                     | `--print=check-cfg`               |
+|-----------------------------------|-----------------------------------|
+| `cfg(foo)`                        | `cfg(foo, values(none()))         |
+| `cfg(foo, values("bar"))`         | `cfg(foo, values("bar"))`         |
+| `cfg(foo, values(none(), "bar"))` | `cfg(foo, values(none(), "bar"))` |
+| `cfg(foo, values(any())`          | `cfg(foo, values(any())`          |
+| `cfg(foo, values())`              | `cfg(foo, values())`              |
+| `cfg(any())`                      | `cfg(any())`                      |
+| *nothing*                         | *nothing*                         |
+
+The print option includes well known cfgs.
 
 To be used like this:
 
 ```bash
 rustc --print=check-cfg -Zunstable-options lib.rs
 ```
 
+> **Note:** Users should be resilient when parsing, in particular against new predicates that
+may be added in the future.
+
 [check-cfg]: https://doc.rust-lang.org/nightly/rustc/check-cfg.html

src/tools/compiletest/src/common.rs

@@ -1065,11 +1065,27 @@ fn builtin_cfg_names(config: &Config) -> HashSet<String> {
         Default::default(),
     )
     .lines()
-    .map(|l| if let Some((name, _)) = l.split_once('=') { name.to_string() } else { l.to_string() })
+    .map(|l| extract_cfg_name(&l).unwrap().to_string())
     .chain(std::iter::once(String::from("test")))
     .collect()
 }
 
+/// Extract the cfg name from `cfg(name, values(...))` lines
+fn extract_cfg_name(check_cfg_line: &str) -> Result<&str, &'static str> {
+    let trimmed = check_cfg_line.trim();
+
+    #[rustfmt::skip]
+    let inner = trimmed
+        .strip_prefix("cfg(")
+        .ok_or("missing cfg(")?
+        .strip_suffix(")")
+        .ok_or("missing )")?;
+
+    let first_comma = inner.find(',').ok_or("no comma found")?;
+
+    Ok(inner[..first_comma].trim())
+}
+
 pub const KNOWN_CRATE_TYPES: &[&str] =
     &["bin", "cdylib", "dylib", "lib", "proc-macro", "rlib", "staticlib"];
 

tests/run-make/print-check-cfg/rmake.rs

@@ -14,51 +14,55 @@ struct CheckCfg {
 
 enum Contains {
     Some { contains: &'static [&'static str], doesnt_contain: &'static [&'static str] },
-    Only(&'static str),
+    Nothing,
 }
 
 fn main() {
-    check(CheckCfg { args: &[], contains: Contains::Only("any()=any()") });
+    check(CheckCfg { args: &[], contains: Contains::Nothing });
     check(CheckCfg {
         args: &["--check-cfg=cfg()"],
         contains: Contains::Some {
-            contains: &["unix", "miri"],
-            doesnt_contain: &["any()", "any()=any()"],
+            contains: &["cfg(unix, values(none()))", "cfg(miri, values(none()))"],
+            doesnt_contain: &["cfg(any())"],
         },
     });
     check(CheckCfg {
         args: &["--check-cfg=cfg(any())"],
         contains: Contains::Some {
-            contains: &["any()", "unix", r#"target_feature="crt-static""#],
+            contains: &["cfg(any())", "cfg(unix, values(none()))"],
             doesnt_contain: &["any()=any()"],
         },
     });
     check(CheckCfg {
         args: &["--check-cfg=cfg(feature)"],
         contains: Contains::Some {
-            contains: &["unix", "miri", "feature"],
-            doesnt_contain: &["any()", "any()=any()", "feature=none()", "feature="],
+            contains: &[
+                "cfg(unix, values(none()))",
+                "cfg(miri, values(none()))",
+                "cfg(feature, values(none()))",
+            ],
+            doesnt_contain: &["cfg(any())", "cfg(feature)"],
         },
     });
     check(CheckCfg {
         args: &[r#"--check-cfg=cfg(feature, values(none(), "", "test", "lol"))"#],
         contains: Contains::Some {
-            contains: &["feature", "feature=\"\"", "feature=\"test\"", "feature=\"lol\""],
-            doesnt_contain: &["any()", "any()=any()", "feature=none()", "feature="],
+            contains: &[r#"cfg(feature, values("", "lol", "test", none()))"#],
+            doesnt_contain: &["cfg(any())", "cfg(feature, values(none()))", "cfg(feature)"],
         },
     });
     check(CheckCfg {
         args: &["--check-cfg=cfg(feature, values())"],
         contains: Contains::Some {
-            contains: &["feature="],
-            doesnt_contain: &["any()", "any()=any()", "feature=none()", "feature"],
+            contains: &["cfg(feature, values())"],
+            doesnt_contain: &["cfg(any())", "cfg(feature, values(none()))", "cfg(feature)"],
         },
     });
     check(CheckCfg {
         args: &["--check-cfg=cfg(feature, values())", "--check-cfg=cfg(feature, values(none()))"],
         contains: Contains::Some {
-            contains: &["feature"],
-            doesnt_contain: &["any()", "any()=any()", "feature=none()", "feature="],
+            contains: &["cfg(feature, values(none()))"],
+            doesnt_contain: &["cfg(any())", "cfg(feature, values())"],
         },
     });
     check(CheckCfg {
@@ -67,8 +71,8 @@ fn main() {
             r#"--check-cfg=cfg(feature, values("tmp"))"#,
         ],
         contains: Contains::Some {
-            contains: &["unix", "miri", "feature=any()"],
-            doesnt_contain: &["any()", "any()=any()", "feature", "feature=", "feature=\"tmp\""],
+            contains: &["cfg(feature, values(any()))"],
+            doesnt_contain: &["cfg(any())", r#"cfg(feature, values("tmp"))"#],
         },
     });
     check(CheckCfg {
@@ -78,8 +82,12 @@ fn main() {
             r#"--check-cfg=cfg(feature, values("tmp"))"#,
         ],
         contains: Contains::Some {
-            contains: &["has_foo", "has_bar", "feature=\"tmp\""],
-            doesnt_contain: &["any()", "any()=any()", "feature"],
+            contains: &[
+                "cfg(has_foo, values(none()))",
+                "cfg(has_bar, values(none()))",
+                r#"cfg(feature, values("tmp"))"#,
+            ],
+            doesnt_contain: &["cfg(any())", "cfg(feature)"],
         },
     });
 }
@@ -94,16 +102,15 @@ fn check(CheckCfg { args, contains }: CheckCfg) {
 
     for l in stdout.lines() {
         assert!(l == l.trim());
-        if let Some((left, right)) = l.split_once('=') {
-            if right != "any()" && right != "" {
-                assert!(right.starts_with("\""));
-                assert!(right.ends_with("\""));
-            }
-            assert!(!left.contains("\""));
-        } else {
-            assert!(!l.contains("\""));
-        }
-        assert!(found.insert(l.to_string()), "{}", &l);
+        assert!(l.starts_with("cfg("), "{l}");
+        assert!(l.ends_with(")"), "{l}");
+        assert_eq!(
+            l.chars().filter(|c| *c == '(').count(),
+            l.chars().filter(|c| *c == ')').count(),
+            "{l}"
+        );
+        assert!(l.chars().filter(|c| *c == '"').count() % 2 == 0, "{l}");
+        assert!(found.insert(l.to_string()), "{l}");
     }
 
     match contains {
@@ -131,9 +138,8 @@ fn check(CheckCfg { args, contains }: CheckCfg) {
                 );
             }
         }
-        Contains::Only(only) => {
-            assert!(found.contains(&only.to_string()), "{:?} != {:?}", &only, &found);
-            assert!(found.len() == 1, "len: {}, instead of 1", found.len());
+        Contains::Nothing => {
+            assert!(found.len() == 0, "len: {}, instead of 0", found.len());
         }
     }
 }