Account for 'cfgs' fixups when evaluating conditional dependencies

Summary:
I need this for the `windows-targets` crate. Version 0.53.3 in microsoft/windows-rs#3670 introduced the following conditional dependency:

```lang=toml
[target.'cfg(windows_raw_dylib)'.dependencies]
windows-link = { version = "0.1.3", default-features = false }
```

If a project were to use a fixup like this:

```lang=toml
# fixups/windows-targets/fixups.toml

cfgs = ["windows_raw_dylib"]
```

then Reindeer needs to know that the `windows-link` dependency applies. Previously, the `cfg(…)` predicate in conditional dependencies was only evaluated based on the cfgs of the platform according to reindeer.toml.

Reviewed By: diliop

Differential Revision: D80892198

fbshipit-source-id: a0567e99fb97fd8f3cb3fce21334743aacc75381

Author: David Tolnay

src/fixups.rs

@@ -148,6 +148,7 @@ impl<'meta> Fixups<'meta> {
             if fixup.platform.eval(
                 &self.config.platform[platform_name],
                 Some(&self.package.version),
+                &BTreeSet::new(),
             ) {
                 configs.push(fixup);
             }

src/index.rs

@@ -422,9 +422,11 @@ impl<'a, 'meta> FeatureResolver<'a, 'meta> {
                     DepKind::Dev => false,
                 }
                 && match &manifest_dep.target {
-                    Some(platform_expr) => {
-                        platform_expr.eval(&self.config.platform[platform_name], None)
-                    }
+                    Some(platform_expr) => platform_expr.eval(
+                        &self.config.platform[platform_name],
+                        None,
+                        &fixups.compute_rustc_cfg(platform_name),
+                    ),
                     None => true,
                 }
                 && !fixups.omit_dep(
@@ -514,8 +516,11 @@ impl<'a, 'meta> FeatureResolver<'a, 'meta> {
                                     DepKind::Dev => false,
                                 }
                                 && match &manifest_dep.target {
-                                    Some(platform_expr) => platform_expr
-                                        .eval(&self.config.platform[platform_name], None),
+                                    Some(platform_expr) => platform_expr.eval(
+                                        &self.config.platform[platform_name],
+                                        None,
+                                        &fixups.compute_rustc_cfg(platform_name),
+                                    ),
                                     None => true,
                                 }
                             {
@@ -597,9 +602,11 @@ impl<'a, 'meta> FeatureResolver<'a, 'meta> {
                     DepKind::Dev => false,
                 }
                 && match &manifest_dep.target {
-                    Some(platform_expr) => {
-                        platform_expr.eval(&self.config.platform[platform_name], None)
-                    }
+                    Some(platform_expr) => platform_expr.eval(
+                        &self.config.platform[platform_name],
+                        None,
+                        &fixups.compute_rustc_cfg(platform_name),
+                    ),
                     None => true,
                 }
             {

src/platform.rs

@@ -275,9 +275,14 @@ impl PlatformExpr {
         Err(anyhow::Error::new(err).context(format!("Bad platform expression `{input}`")))
     }
 
-    pub fn eval(&self, config: &PlatformConfig, version: Option<&Version>) -> bool {
+    pub fn eval(
+        &self,
+        config: &PlatformConfig,
+        version: Option<&Version>,
+        extra_cfg: &BTreeSet<String>,
+    ) -> bool {
         match self {
-            PlatformExpr::Bool { key } => config.cfg.contains_key(key),
+            PlatformExpr::Bool { key } => config.cfg.contains_key(key) || extra_cfg.contains(key),
             PlatformExpr::Value { key, value } => {
                 if key == "feature" {
                     // [target.'cfg(feature = "...")'.dependencies] never get applied by Cargo
@@ -291,19 +296,23 @@ impl PlatformExpr {
                 Some(version) => req.matches(version),
             },
             PlatformExpr::Target(target) => config.target.as_ref() == Some(target),
-            PlatformExpr::Not(pred) => !pred.eval(config, version),
-            PlatformExpr::Any(preds) => preds.iter().any(|pred| pred.eval(config, version)),
-            PlatformExpr::All(preds) => preds.iter().all(|pred| pred.eval(config, version)),
+            PlatformExpr::Not(pred) => !pred.eval(config, version, extra_cfg),
+            PlatformExpr::Any(preds) => preds
+                .iter()
+                .any(|pred| pred.eval(config, version, extra_cfg)),
+            PlatformExpr::All(preds) => preds
+                .iter()
+                .all(|pred| pred.eval(config, version, extra_cfg)),
             PlatformExpr::Unix => PlatformExpr::Value {
                 key: "target_family".to_owned(),
                 value: "unix".to_owned(),
             }
-            .eval(config, version),
+            .eval(config, version, extra_cfg),
             PlatformExpr::Windows => PlatformExpr::Value {
                 key: "target_family".to_owned(),
                 value: "windows".to_owned(),
             }
-            .eval(config, version),
+            .eval(config, version, extra_cfg),
         }
     }
 }