1 files changed, 27 insertions, 13 deletions
diff --git a/crate_universe/src/utils/starlark/glob.rs b/crate_universe/src/utils/starlark/glob.rs
index a7bcebbb..c8bf4bf5 100644
--- a/crate_universe/src/utils/starlark/glob.rs
+++ b/crate_universe/src/utils/starlark/glob.rs
@@ -6,20 +6,22 @@ use serde::de::{Deserialize, Deserializer, MapAccess, SeqAccess, Visitor};
 use serde::ser::{Serialize, SerializeStruct, Serializer};
 
 #[derive(Debug, Default, PartialEq, Eq, PartialOrd, Ord, Clone)]
-pub struct Glob {
-    pub include: BTreeSet<String>,
-    pub exclude: BTreeSet<String>,
+pub(crate) struct Glob {
+    pub(crate) allow_empty: bool,
+    pub(crate) include: BTreeSet<String>,
+    pub(crate) exclude: BTreeSet<String>,
 }
 
 impl Glob {
-    pub fn new_rust_srcs() -> Self {
+    pub(crate) fn new_rust_srcs() -> Self {
         Self {
+            allow_empty: false,
             include: BTreeSet::from(["**/*.rs".to_owned()]),
             exclude: BTreeSet::new(),
         }
     }
 
-    pub fn is_empty(&self) -> bool {
+    pub(crate) fn has_any_include(&self) -> bool {
         self.include.is_empty()
         // Note: self.exclude intentionally not considered. A glob is empty if
         // there are no included globs. A glob cannot have only excludes.
@@ -31,16 +33,17 @@ impl Serialize for Glob {
     where
         S: Serializer,
     {
-        if self.exclude.is_empty() {
-            // Serialize as glob([...]).
-            serializer.serialize_newtype_struct("glob", &self.include)
-        } else {
-            // Serialize as glob(include = [...], exclude = [...]).
-            let mut call = serializer.serialize_struct("glob", 2)?;
-            call.serialize_field("include", &self.include)?;
+        let has_exclude = !self.exclude.is_empty();
+        let len = 2 + if has_exclude { 1 } else { 0 };
+
+        // Serialize as glob(allow_empty = False, include = [...], exclude = [...]).
+        let mut call = serializer.serialize_struct("glob", len)?;
+        call.serialize_field("allow_empty", &self.allow_empty)?;
+        call.serialize_field("include", &self.include)?;
+        if has_exclude {
             call.serialize_field("exclude", &self.exclude)?;
-            call.end()
         }
+        call.end()
     }
 }
 
@@ -68,6 +71,9 @@ impl<'de> Visitor<'de> for GlobVisitor {
         A: SeqAccess<'de>,
     {
         Ok(Glob {
+            // At time of writing the default value of allow_empty is true.
+            // We may want to change this if the default changes in Bazel.
+            allow_empty: true,
             include: BTreeSet::deserialize(SeqAccessDeserializer::new(seq))?,
             exclude: BTreeSet::new(),
         })
@@ -78,14 +84,22 @@ impl<'de> Visitor<'de> for GlobVisitor {
     where
         A: MapAccess<'de>,
     {
+        fn default_true() -> bool {
+            true
+        }
+
         #[derive(serde::Deserialize)]
         struct GlobMap {
+            #[serde(default = "default_true")]
+            allow_empty: bool,
             include: BTreeSet<String>,
+            #[serde(default)]
             exclude: BTreeSet<String>,
         }
 
         let glob_map = GlobMap::deserialize(MapAccessDeserializer::new(map))?;
         Ok(Glob {
+            allow_empty: glob_map.allow_empty,
             include: glob_map.include,
             exclude: glob_map.exclude,
         })