Allow enabling config-include feature in config

Prior to this change, it is not possible to enable the unstable
`config-include` flag from within a config file itself. This is due to
the fact that, while cargo does reload configuration files if this
flag is set, it does not parse the top-level configuration file's
unstable flags before checking whether this flag is present.

This commit forces cargo to load unstable features before this check,
and if the flag is present, re-loads configuration files with
`config-include` enabled.

Author: lschuermann

src/cargo/util/context/mod.rs

@@ -1035,6 +1035,11 @@ impl GlobalContext {
             self.cli_config = Some(cli_config.iter().map(|s| s.to_string()).collect());
             self.merge_cli_args()?;
         }
+
+        // Load the unstable flags from config file here first, as the config
+        // file itself may enable inclusion of other configs. In that case, we
+        // want to re-load configs with includes enabled:
+        self.load_unstable_flags_from_config()?;
         if self.unstable_flags.config_include {
             // If the config was already loaded (like when fetching the
             // `[alias]` table), it was loaded with includes disabled because
@@ -1091,8 +1096,6 @@ impl GlobalContext {
         let cli_target_dir = target_dir.as_ref().map(|dir| Filesystem::new(dir.clone()));
         self.target_dir = cli_target_dir;
 
-        self.load_unstable_flags_from_config()?;
-
         Ok(())
     }
 

tests/testsuite/config_include.rs

@@ -72,11 +72,9 @@ fn enable_in_unstable_config() {
     let gctx = GlobalContextBuilder::new()
         .nightly_features_allowed(true)
         .build();
-    // On this commit, enabling `config-include` in the top-level
-    // configuration does not yet work.
     assert_eq!(gctx.get::<i32>("key1").unwrap(), 1);
     assert_eq!(gctx.get::<i32>("key2").unwrap(), 2);
-    assert_eq!(gctx.get::<i32>("key3").ok(), None);
+    assert_eq!(gctx.get::<i32>("key3").unwrap(), 4);
 }
 
 #[cargo_test]
@@ -200,15 +198,18 @@ fn mix_of_hierarchy_and_include_with_enable_in_unstable_config() {
         .cwd("foo")
         .nightly_features_allowed(true)
         .build();
-    // On this commit, enabling `config-include` in the top-level
-    // configuration does not yet work.
     assert_eq!(gctx.get::<i32>("key1").unwrap(), 1);
-    assert_eq!(gctx.get::<i32>("key2").unwrap(), 3);
+    assert_eq!(gctx.get::<i32>("key2").unwrap(), 2);
     assert_eq!(gctx.get::<i32>("key3").unwrap(), 3);
-    assert_eq!(gctx.get::<i32>("key4").ok(), None);
+    assert_eq!(gctx.get::<i32>("key4").unwrap(), 4);
     assert_eq!(
         gctx.get::<Vec<String>>("unstable.features").unwrap(),
-        vec!["3".to_string(), "1".to_string()]
+        vec![
+            "4".to_string(),
+            "3".to_string(),
+            "2".to_string(),
+            "1".to_string()
+        ]
     );
 }