Implement --randomize-powerset feature

Cargo.toml

@@ -28,6 +28,7 @@ pkg-fmt = "tgz"
 anyhow = "1.0.47"
 cargo-config2 = "0.1.13"
 ctrlc = { version = "3.4.4", features = ["termination"] }
+fastrand = "2.3.0"
 lexopt = "0.3"
 same-file = "1.0.1"
 serde_json = "1"

README.md

@@ -77,6 +77,13 @@ OPTIONS:
             --include-features and there are multiple features, this also includes runs with just
             --all-features flag.
 
+        --randomize-powerset <seed>
+            Randomize order of powerset elements.
+
+            Run feature powerset in random order with the specified seed.
+
+            Zero seed value means unseeded.
+
         --optional-deps [DEPS]...
             Use optional dependencies as features.
 

src/cli.rs

@@ -101,6 +101,9 @@ pub(crate) struct Args {
     // propagated to cargo (as a part of leading_args)
     /// --no-default-features
     pub(crate) no_default_features: bool,
+
+    /// --randomize-powerset
+    pub(crate) randomize_powerset: Option<u64>,
 }
 
 impl Args {
@@ -177,6 +180,8 @@ impl Args {
         let mut exclude_no_default_features = false;
         let mut exclude_all_features = false;
 
+        let mut randomize_powerset = None;
+
         let mut group_features: Vec<String> = vec![];
         let mut mutually_exclusive_features: Vec<String> = vec![];
         let mut depth = None;
@@ -303,6 +308,7 @@ impl Args {
                 Long("remove-dev-deps") => parse_flag!(remove_dev_deps),
                 Long("each-feature") => parse_flag!(each_feature),
                 Long("feature-powerset") => parse_flag!(feature_powerset),
+                Long("randomize-powerset") => parse_opt!(randomize_powerset, false),
                 Long("at-least-one-of") => at_least_one_of.push(parser.value()?.parse()?),
                 Long("no-private") => parse_flag!(no_private),
                 Long("ignore-private") => parse_flag!(ignore_private),
@@ -487,6 +493,10 @@ impl Args {
         if each_feature && feature_powerset {
             conflicts("--each-feature", "--feature-powerset")?;
         }
+
+        let randomize_powerset =
+            randomize_powerset.as_deref().map(str::parse::<u64>).transpose()?;
+
         if all_features {
             if each_feature {
                 conflicts("--all-features", "--each-feature")?;
@@ -644,6 +654,8 @@ impl Args {
 
             no_default_features,
             target: target.into_iter().collect(),
+
+            randomize_powerset,
         })
     }
 }
@@ -695,6 +707,10 @@ const HELP: &[HelpText<'_>] = &[
          --include-features and there are multiple features, this also includes runs with just \
          --all-features flag."
     ]),
+    ("", "--randomize-powerset", "<seed>", "Randomize order of powerset elements", &[
+        "Run feature powerset in random order with the specified seed.",
+        "Zero seed value means unseeded."
+    ]),
     ("", "--optional-deps", "[DEPS]...", "Use optional dependencies as features", &[
         "If DEPS are not specified, all optional dependencies are considered as features.",
         "This flag can only be used together with either --each-feature flag or --feature-powerset \

src/features.rs

@@ -210,11 +210,12 @@ pub(crate) fn feature_powerset<'a>(
     at_least_one_of: &[Feature],
     mutually_exclusive_features: &[Feature],
     package_features: &BTreeMap<String, Vec<String>>,
+    randomize: Option<u64>,
 ) -> Vec<Vec<&'a Feature>> {
     let deps_map = feature_deps(package_features);
     let at_least_one_of = at_least_one_of_for_package(at_least_one_of, &deps_map);
 
-    powerset(features, depth)
+    let mut result: Vec<Vec<&'a Feature>> = powerset(features, depth)
         .into_iter()
         .skip(1) // The first element of a powerset is `[]` so it should be skipped.
         .filter(|fs| {
@@ -249,7 +250,14 @@ pub(crate) fn feature_powerset<'a>(
             }
             true
         })
-        .collect()
+        .collect();
+    if let Some(seed) = randomize {
+        if seed != 0 {
+            fastrand::seed(seed);
+        }
+        fastrand::shuffle(&mut result);
+    }
+    result
 }
 
 fn feature_deps(map: &BTreeMap<String, Vec<String>>) -> BTreeMap<&str, BTreeSet<&str>> {
@@ -366,22 +374,22 @@ mod tests {
         let map = map![("a", v![]), ("b", v!["a"]), ("c", v!["b"]), ("d", v!["a", "b"])];
 
         let list = v!["a", "b", "c", "d"];
-        let filtered = feature_powerset(&list, None, &[], &[], &map);
+        let filtered = feature_powerset(&list, None, &[], &[], &map, None);
         assert_eq!(filtered, vec![vec!["a"], vec!["b"], vec!["c"], vec!["d"], vec!["c", "d"]]);
 
-        let filtered = feature_powerset(&list, None, &["a".into()], &[], &map);
+        let filtered = feature_powerset(&list, None, &["a".into()], &[], &map, None);
         assert_eq!(filtered, vec![vec!["a"], vec!["b"], vec!["c"], vec!["d"], vec!["c", "d"]]);
 
-        let filtered = feature_powerset(&list, None, &["c".into()], &[], &map);
+        let filtered = feature_powerset(&list, None, &["c".into()], &[], &map, None);
         assert_eq!(filtered, vec![vec!["c"], vec!["c", "d"]]);
 
-        let filtered = feature_powerset(&list, None, &["a".into(), "c".into()], &[], &map);
+        let filtered = feature_powerset(&list, None, &["a".into(), "c".into()], &[], &map, None);
         assert_eq!(filtered, vec![vec!["c"], vec!["c", "d"]]);
 
         let map = map![("tokio", v![]), ("async-std", v![]), ("a", v![]), ("b", v!["a"])];
         let list = v!["a", "b", "tokio", "async-std"];
         let mutually_exclusive_features = [Feature::group(["tokio", "async-std"])];
-        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map);
+        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map, None);
         assert_eq!(filtered, vec![
             vec!["a"],
             vec!["b"],
@@ -395,7 +403,7 @@ mod tests {
 
         let mutually_exclusive_features =
             [Feature::group(["tokio", "a"]), Feature::group(["tokio", "async-std"])];
-        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map);
+        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map, None);
         assert_eq!(filtered, vec![
             vec!["a"],
             vec!["b"],
@@ -413,7 +421,7 @@ mod tests {
         ];
         let list = v!["a", "b", "tokio", "async-std"];
         let mutually_exclusive_features = [Feature::group(["tokio", "async-std"])];
-        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map);
+        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map, None);
         assert_eq!(filtered, vec![
             vec!["a"],
             vec!["b"],
@@ -427,7 +435,7 @@ mod tests {
         let map = map![("a", v![]), ("b", v!["a"]), ("c", v![]), ("d", v!["b"])];
         let list = v!["a", "b", "c", "d"];
         let mutually_exclusive_features = [Feature::group(["a", "c"])];
-        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map);
+        let filtered = feature_powerset(&list, None, &[], &mutually_exclusive_features, &map, None);
         assert_eq!(filtered, vec![vec!["a"], vec!["b"], vec!["c"], vec!["d"]]);
     }
 
@@ -461,7 +469,7 @@ mod tests {
             vec!["b", "c", "d"],
             vec!["a", "b", "c", "d"],
         ]);
-        let filtered = feature_powerset(&list, None, &[], &[], &map);
+        let filtered = feature_powerset(&list, None, &[], &[], &map, None);
         assert_eq!(filtered, vec![vec!["a"], vec!["b"], vec!["c"], vec!["d"], vec!["c", "d"]]);
     }
 

src/main.rs

@@ -289,6 +289,7 @@ fn determine_kind<'a>(
             &cx.at_least_one_of,
             &cx.mutually_exclusive_features,
             &package.features,
+            cx.randomize_powerset,
         );
 
         if (pkg_features.normal().is_empty() && pkg_features.optional_deps().is_empty()

tests/long-help.txt

@@ -47,6 +47,13 @@ OPTIONS:
             --include-features and there are multiple features, this also includes runs with just
             --all-features flag.
 
+        --randomize-powerset <seed>
+            Randomize order of powerset elements.
+
+            Run feature powerset in random order with the specified seed.
+
+            Zero seed value means unseeded.
+
         --optional-deps [DEPS]...
             Use optional dependencies as features.
 

tests/short-help.txt

@@ -16,6 +16,7 @@ OPTIONS:
     -F, --features <FEATURES>...         Space or comma separated list of features to activate
         --each-feature                   Perform for each feature of the package
         --feature-powerset               Perform for the feature powerset of the package
+        --randomize-powerset <seed>      Randomize order of powerset elements
         --optional-deps [DEPS]...        Use optional dependencies as features
         --skip <FEATURES>...             Alias for --exclude-features
         --exclude-features <FEATURES>... Space or comma separated list of features to exclude