Lint against unexpected cfgs in [target.'cfg(...)']

crates/cargo-platform/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cargo-platform"
-version = "0.2.0"
+version = "0.2.1"
 edition.workspace = true
 license.workspace = true
 rust-version.workspace = true

crates/cargo-platform/src/cfg.rs

@@ -149,6 +149,28 @@ impl CfgExpr {
             CfgExpr::Value(ref e) => cfg.contains(e),
         }
     }
+
+    /// Walk over all the `Cfg`s of the given `CfgExpr`, recursing into `not(...)`, `all(...)`,
+    /// `any(...)` and stopping at the first error and returning that error.
+    pub fn walk<E>(&self, mut f: impl FnMut(&Cfg) -> Result<(), E>) -> Result<(), E> {
+        fn walk_inner<E>(
+            cfg_expr: &CfgExpr,
+            f: &mut impl FnMut(&Cfg) -> Result<(), E>,
+        ) -> Result<(), E> {
+            match *cfg_expr {
+                CfgExpr::Not(ref e) => walk_inner(e, &mut *f),
+                CfgExpr::All(ref e) | CfgExpr::Any(ref e) => {
+                    for e in e {
+                        let _ = walk_inner(e, &mut *f)?;
+                    }
+                    Ok(())
+                }
+                CfgExpr::Value(ref e) => f(e),
+            }
+        }
+
+        walk_inner(self, &mut f)
+    }
 }
 
 impl FromStr for CfgExpr {

crates/cargo-platform/src/check_cfg.rs

@@ -0,0 +1,98 @@
+//! check-cfg
+
+use std::{
+    collections::{HashMap, HashSet},
+    error::Error,
+    fmt::Display,
+};
+
+/// Check Config (aka `--check-cfg`/`--print=check-cfg` representation)
+#[derive(Debug, Default, Clone)]
+pub struct CheckCfg {
+    /// Is `--check-cfg` activated
+    pub exhaustive: bool,
+    /// List of expected cfgs
+    pub expecteds: HashMap<String, ExpectedValues>,
+}
+
+/// List of expected check-cfg values
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ExpectedValues {
+    /// List of expected values
+    ///
+    ///  - `#[cfg(foo)]` value is `None`
+    ///  - `#[cfg(foo = "")]` value is `Some("")`
+    ///  - `#[cfg(foo = "bar")]` value is `Some("bar")`
+    Some(HashSet<Option<String>>),
+    /// All values expected
+    Any,
+}
+
+/// Error when parse a line from `--print=check-cfg`
+#[derive(Debug)]
+#[non_exhaustive]
+pub struct PrintCheckCfgParsingError;
+
+impl Error for PrintCheckCfgParsingError {}
+
+impl Display for PrintCheckCfgParsingError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str("error when parsing a `--print=check-cfg` line")
+    }
+}
+
+impl CheckCfg {
+    /// Parse a line from `--print=check-cfg`
+    pub fn parse_print_check_cfg_line(
+        &mut self,
+        line: &str,
+    ) -> Result<(), PrintCheckCfgParsingError> {
+        if line == "any()=any()" || line == "any()" {
+            self.exhaustive = false;
+            return Ok(());
+        }
+
+        let mut value: HashSet<Option<String>> = HashSet::default();
+        let mut value_any_specified = false;
+        let name: String;
+
+        if let Some((n, val)) = line.split_once('=') {
+            name = n.to_string();
+
+            if val == "any()" {
+                value_any_specified = true;
+            } else if val.is_empty() {
+                // no value, nothing to add
+            } else if let Some(val) = maybe_quoted_value(val) {
+                value.insert(Some(val.to_string()));
+            } else {
+                // missing quotes and non-empty
+                return Err(PrintCheckCfgParsingError);
+            }
+        } else {
+            name = line.to_string();
+            value.insert(None);
+        }
+
+        self.expecteds
+            .entry(name)
+            .and_modify(|v| match v {
+                ExpectedValues::Some(_) if value_any_specified => *v = ExpectedValues::Any,
+                ExpectedValues::Some(v) => v.extend(value.clone()),
+                ExpectedValues::Any => {}
+            })
+            .or_insert_with(|| {
+                if value_any_specified {
+                    ExpectedValues::Any
+                } else {
+                    ExpectedValues::Some(value)
+                }
+            });
+        Ok(())
+    }
+}
+
+fn maybe_quoted_value<'a>(v: &'a str) -> Option<&'a str> {
+    // strip "" around the value, e.g. "linux" -> linux
+    v.strip_prefix('"').and_then(|v| v.strip_suffix('"'))
+}

crates/cargo-platform/src/lib.rs

@@ -15,10 +15,12 @@ use std::str::FromStr;
 use std::{fmt, path::Path};
 
 mod cfg;
+mod check_cfg;
 mod error;
 
 use cfg::KEYWORDS;
 pub use cfg::{Cfg, CfgExpr, Ident};
+pub use check_cfg::{CheckCfg, ExpectedValues};
 pub use error::{ParseError, ParseErrorKind};
 
 /// Platform definition.

crates/cargo-platform/tests/test_print_check_cfg.rs

@@ -0,0 +1,123 @@
+use cargo_platform::{CheckCfg, ExpectedValues};
+use std::collections::HashSet;
+
+#[test]
+fn print_check_cfg_none() {
+    let mut check_cfg = CheckCfg::default();
+
+    check_cfg.parse_print_check_cfg_line("cfg_a").unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_a").unwrap(),
+        ExpectedValues::Some(HashSet::from([None]))
+    );
+}
+
+#[test]
+fn print_check_cfg_empty() {
+    let mut check_cfg = CheckCfg::default();
+
+    check_cfg.parse_print_check_cfg_line("cfg_b=").unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_b").unwrap(),
+        ExpectedValues::Some(HashSet::from([]))
+    );
+}
+
+#[test]
+fn print_check_cfg_any() {
+    let mut check_cfg = CheckCfg::default();
+
+    check_cfg.parse_print_check_cfg_line("cfg_c=any()").unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_c").unwrap(),
+        ExpectedValues::Any
+    );
+
+    check_cfg.parse_print_check_cfg_line("cfg_c").unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_c").unwrap(),
+        ExpectedValues::Any
+    );
+}
+
+#[test]
+fn print_check_cfg_value() {
+    let mut check_cfg = CheckCfg::default();
+
+    check_cfg
+        .parse_print_check_cfg_line("cfg_d=\"test\"")
+        .unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_d").unwrap(),
+        ExpectedValues::Some(HashSet::from([Some("test".to_string())]))
+    );
+
+    check_cfg
+        .parse_print_check_cfg_line("cfg_d=\"tmp\"")
+        .unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_d").unwrap(),
+        ExpectedValues::Some(HashSet::from([
+            Some("test".to_string()),
+            Some("tmp".to_string())
+        ]))
+    );
+}
+
+#[test]
+fn print_check_cfg_none_and_value() {
+    let mut check_cfg = CheckCfg::default();
+
+    check_cfg.parse_print_check_cfg_line("cfg").unwrap();
+    check_cfg.parse_print_check_cfg_line("cfg=\"foo\"").unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg").unwrap(),
+        ExpectedValues::Some(HashSet::from([None, Some("foo".to_string())]))
+    );
+}
+
+#[test]
+fn print_check_cfg_quote_in_value() {
+    let mut check_cfg = CheckCfg::default();
+
+    check_cfg
+        .parse_print_check_cfg_line("cfg_e=\"quote_in_value\"\"")
+        .unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_e").unwrap(),
+        ExpectedValues::Some(HashSet::from([Some("quote_in_value\"".to_string())]))
+    );
+}
+
+#[test]
+fn print_check_cfg_value_and_any() {
+    let mut check_cfg = CheckCfg::default();
+
+    // having both a value and `any()` shouldn't be possible but better
+    // handle this correctly anyway
+
+    check_cfg
+        .parse_print_check_cfg_line("cfg_1=\"foo\"")
+        .unwrap();
+    check_cfg.parse_print_check_cfg_line("cfg_1=any()").unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_1").unwrap(),
+        ExpectedValues::Any
+    );
+
+    check_cfg.parse_print_check_cfg_line("cfg_2=any()").unwrap();
+    check_cfg
+        .parse_print_check_cfg_line("cfg_2=\"foo\"")
+        .unwrap();
+    assert_eq!(
+        *check_cfg.expecteds.get("cfg_2").unwrap(),
+        ExpectedValues::Any
+    );
+}
+
+#[test]
+#[should_panic]
+fn print_check_cfg_missing_quote_value() {
+    let mut check_cfg = CheckCfg::default();
+    check_cfg.parse_print_check_cfg_line("foo=bar").unwrap();
+}