fix(migrate-eslint): allow null in file lists (#4749)

CHANGELOG.md

@@ -38,6 +38,9 @@ our [guidelines for writing a good changelog entry](https://github.com/biomejs/b
 
   Contributed by @Conaclos
 
+- `biome migrate eslint` now correctly handles ESLint configuration with `null` values in file lists ([#4740](https://github.com/biomejs/biome/issues/4740)).
+  Contributed by @Conaclos
+
 ### Configuration
 
 ### Editors

crates/biome_cli/src/execute/migrate/eslint_eslint.rs

@@ -43,9 +43,9 @@ pub(crate) struct FlatConfigData(pub(crate) Vec<FlatConfigObject>);
 #[derive(Debug, Default, Deserializable)]
 #[deserializable(unknown_fields = "allow")]
 pub(crate) struct FlatConfigObject {
-    pub(crate) files: Vec<String>,
+    pub(crate) files: ShorthandVec<String>,
     /// The glob patterns that ignore to lint.
-    pub(crate) ignores: Vec<String>,
+    pub(crate) ignores: ShorthandVec<String>,
     // using `Option` is important to distinguish a global ignores from a config objerct
     pub(crate) language_options: Option<FlatLanguageOptions>,
     // using `Option` is important to distinguish a global ignores from a config objerct
@@ -240,6 +240,11 @@ impl<T> DerefMut for ShorthandVec<T> {
         &mut self.0
     }
 }
+impl<T> FromIterator<T> for ShorthandVec<T> {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
+        Self(iter.into_iter().collect())
+    }
+}
 impl<T> IntoIterator for ShorthandVec<T> {
     type Item = T;
     type IntoIter = vec::IntoIter<T>;
@@ -255,9 +260,14 @@ impl<T: Deserializable> Deserializable for ShorthandVec<T> {
     ) -> Option<Self> {
         Some(ShorthandVec(
             if value.visitable_type()? == DeserializableType::Array {
-                Deserializable::deserialize(value, name, diagnostics)?
+                <Vec<Option<T>>>::deserialize(value, name, diagnostics)?
+                    .into_iter()
+                    .flatten()
+                    .collect()
             } else {
-                Vec::from_iter([Deserializable::deserialize(value, name, diagnostics)?])
+                <Option<T>>::deserialize(value, name, diagnostics)?
+                    .into_iter()
+                    .collect()
             },
         ))
     }

crates/biome_cli/src/execute/migrate/eslint_to_biome.rs

@@ -323,8 +323,8 @@ mod tests {
     #[test]
     fn flat_config_single_config_object() {
         let flat_config = FlatConfigData(vec![FlatConfigObject {
-            files: vec!["*.js".to_string()],
-            ignores: vec!["*.test.js".to_string()],
+            files: ["*.js".to_string()].into_iter().collect(),
+            ignores: ["*.test.js".to_string()].into_iter().collect(),
             language_options: None,
             rules: Some(Rules(
                 [Rule::Any(Cow::Borrowed("eqeqeq"), Severity::Error)]
@@ -354,14 +354,14 @@ mod tests {
     fn flat_config_multiple_config_object() {
         let flat_config = FlatConfigData(vec![
             FlatConfigObject {
-                files: vec![],
-                ignores: vec!["*.test.js".to_string()],
+                files: ShorthandVec::default(),
+                ignores: ["*.test.js".to_string()].into_iter().collect(),
                 language_options: None,
                 rules: None,
             },
             FlatConfigObject {
-                files: vec![],
-                ignores: vec![],
+                files: ShorthandVec::default(),
+                ignores: ShorthandVec::default(),
                 language_options: None,
                 rules: Some(Rules(
                     [Rule::Any(Cow::Borrowed("eqeqeq"), Severity::Error)]
@@ -370,14 +370,14 @@ mod tests {
                 )),
             },
             FlatConfigObject {
-                files: vec![],
-                ignores: vec!["*.spec.js".to_string()],
+                files: ShorthandVec::default(),
+                ignores: ["*.spec.js".to_string()].into_iter().collect(),
                 language_options: None,
                 rules: None,
             },
             FlatConfigObject {
-                files: vec!["*.ts".to_string()],
-                ignores: vec![],
+                files: ["*.ts".to_string()].into_iter().collect(),
+                ignores: ShorthandVec::default(),
                 language_options: None,
                 rules: Some(Rules(
                     [Rule::Any(Cow::Borrowed("eqeqeq"), Severity::Off)]

crates/biome_cli/tests/commands/migrate_eslint.rs

@@ -676,7 +676,7 @@ fn migrate_merge_with_overrides() {
     }"#;
     let eslintrc = r#"{
         "overrides": [{
-            "files": ["bin/*.js", "lib/*.js"],
+            "files": ["bin/*.js", "lib/*.js", null],
             "excludedFiles": "*.test.js",
             "rules": {
                 "eqeqeq": ["off"]

crates/biome_cli/tests/snapshots/main_commands_migrate_eslint/migrate_merge_with_overrides.snap

@@ -1,6 +1,7 @@
 ---
 source: crates/biome_cli/tests/snap_test.rs
 expression: content
+snapshot_kind: text
 ---
 ## `biome.json`
 
@@ -20,7 +21,7 @@ expression: content
 ```json
 {
         "overrides": [{
-            "files": ["bin/*.js", "lib/*.js"],
+            "files": ["bin/*.js", "lib/*.js", null],
             "excludedFiles": "*.test.js",
             "rules": {
                 "eqeqeq": ["off"]

crates/biome_deserialize/src/impls.rs

@@ -534,7 +534,11 @@ impl<T: Deserializable> Deserializable for Option<T> {
         name: &str,
         diagnostics: &mut Vec<DeserializationDiagnostic>,
     ) -> Option<Self> {
-        T::deserialize(value, name, diagnostics).map(Option::Some)
+        if value.visitable_type() == Some(crate::DeserializableType::Null) {
+            None
+        } else {
+            T::deserialize(value, name, diagnostics).map(Option::Some)
+        }
     }
 }