fix(formatter): align conditional type formatting with Prettier

.changeset/honest-eagles-learn.md

@@ -0,0 +1,22 @@
+---
+"@biomejs/biome": patch
+---
+
+Fixed [#7806](https://github.com/biomejs/biome/issues/7806): Prefer breaking after the assignment operator for conditional types with generic parameters to match Prettier.
+
+```diff
+-type True = unknown extends Type<
+-  "many",
+-  "generic",
+-  "parameters",
+-  "one",
+-  "two",
+-  "three"
+->
+-  ? true
+-  : false;
++type True =
++  unknown extends Type<"many", "generic", "parameters", "one", "two", "three">
++    ? true
++    : false;
+```

crates/biome_js_formatter/src/utils/assignment_like.rs

@@ -16,9 +16,9 @@ use biome_js_syntax::{
     JsInitializerClause, JsLiteralMemberName, JsObjectAssignmentPattern,
     JsObjectAssignmentPatternProperty, JsObjectBindingPattern, JsPropertyClassMember,
     JsPropertyClassMemberFields, JsPropertyObjectMember, JsSyntaxKind, JsVariableDeclarator,
-    TsInitializedPropertySignatureClassMember, TsInitializedPropertySignatureClassMemberFields,
-    TsPropertySignatureClassMember, TsPropertySignatureClassMemberFields, TsTypeAliasDeclaration,
-    TsTypeArguments, TsUnionType,
+    TsConditionalType, TsInitializedPropertySignatureClassMember,
+    TsInitializedPropertySignatureClassMemberFields, TsPropertySignatureClassMember,
+    TsPropertySignatureClassMemberFields, TsTypeAliasDeclaration, TsTypeArguments, TsUnionType,
 };
 use biome_js_syntax::{AnyJsLiteralExpression, JsUnaryExpression};
 use biome_rowan::{AstNode, SyntaxNodeOptionExt, SyntaxResult, declare_node_union};
@@ -931,13 +931,34 @@ impl AnyJsAssignmentLike {
                 }
                 has_leading_comments
             }
+            RightAssignmentLike::AnyTsType(AnyTsType::TsConditionalType(conditional_type)) => {
+                comments.has_leading_own_line_comment(conditional_type.syntax())
+                    || should_break_before_conditional_type(conditional_type)?
+            }
             right => comments.has_leading_own_line_comment(right.syntax()),
         };
 
         Ok(result)
     }
 }
 
+fn is_generic(ty: &AnyTsType) -> bool {
+    match ty {
+        AnyTsType::TsReferenceType(reference) => reference.type_arguments().is_some(),
+        AnyTsType::TsFunctionType(function) => function.type_parameters().is_some(),
+        _ => false,
+    }
+}
+
+fn should_break_before_conditional_type(
+    conditional_type: &TsConditionalType,
+) -> SyntaxResult<bool> {
+    Ok(
+        is_generic(&conditional_type.check_type()?)
+            || is_generic(&conditional_type.extends_type()?),
+    )
+}
+
 /// Checks if the function is entitled to be printed with layout [AssignmentLikeLayout::BreakAfterOperator]
 pub(crate) fn should_break_after_operator(
     right: &AnyJsExpression,

crates/biome_js_formatter/tests/specs/prettier/typescript/type-alias/conditional.ts.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/biome_formatter_test/src/snapshot_builder.rs
+assertion_line: 211
 info: typescript/type-alias/conditional.ts
 ---
 # Input
@@ -48,35 +49,9 @@ export type Intersect<U1 extends any, U2 extends any> =
 ```diff
 --- Prettier
 +++ Biome
-@@ -1,18 +1,27 @@
--type FallbackFlags<F extends Flags | undefined> =
--  Equals<NonNullableFlag<F>["flags"], {}> extends true
--    ? Dict<any>
--    : NonNullableFlag<F>["flags"];
-+type FallbackFlags<F extends Flags | undefined> = Equals<
-+  NonNullableFlag<F>["flags"],
-+  {}
-+> extends true
-+  ? Dict<any>
-+  : NonNullableFlag<F>["flags"];
-
--export type UnPromise<Type extends Promise<unknown>> =
--  Type extends Promise<infer Generic> ? Generic : never;
-+export type UnPromise<Type extends Promise<unknown>> = Type extends Promise<
-+  infer Generic
-+>
-+  ? Generic
-+  : never;
-
--export type Equals<X, Y> =
--  (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y ? 1 : 2
--    ? true
--    : false;
-+export type Equals<X, Y> = (<T>() => T extends X ? 1 : 2) extends <
-+  T,
-+>() => T extends Y ? 1 : 2
-+  ? true
-+  : false;
+@@ -11,8 +11,11 @@
+     ? true
+     : false;
 
 -export type _Repeat<A extends any, N extends number, L extends List = []> =
 -  __Repeat<N, A, L> extends infer X ? Cast<X, List> : never;
@@ -93,24 +68,18 @@ export type Intersect<U1 extends any, U2 extends any> =
 # Output
 
 ```ts
-type FallbackFlags<F extends Flags | undefined> = Equals<
-  NonNullableFlag<F>["flags"],
-  {}
-> extends true
-  ? Dict<any>
-  : NonNullableFlag<F>["flags"];
-
-export type UnPromise<Type extends Promise<unknown>> = Type extends Promise<
-  infer Generic
->
-  ? Generic
-  : never;
+type FallbackFlags<F extends Flags | undefined> =
+  Equals<NonNullableFlag<F>["flags"], {}> extends true
+    ? Dict<any>
+    : NonNullableFlag<F>["flags"];
 
-export type Equals<X, Y> = (<T>() => T extends X ? 1 : 2) extends <
-  T,
->() => T extends Y ? 1 : 2
-  ? true
-  : false;
+export type UnPromise<Type extends Promise<unknown>> =
+  Type extends Promise<infer Generic> ? Generic : never;
+
+export type Equals<X, Y> =
+  (<T>() => T extends X ? 1 : 2) extends <T>() => T extends Y ? 1 : 2
+    ? true
+    : false;
 
 export type _Repeat<
   A extends any,

crates/biome_js_formatter/tests/specs/ts/type/conditional.ts

@@ -14,4 +14,30 @@ type T4 = test extends string
     // something
     ? unknown : test extends number ? undefined :
         // else
-        undefined;
+        undefined;
+
+type T5 =
+    // comment
+    test extends string ? test extends number ? unknown : unknown : undefined;
+
+type Echo<T> = T
+
+type T6 = test extends Echo<string> ? test extends number ? unknown : unknown : undefined;
+
+type T7 = test extends Echo<string> ?  unknown : test extends number ? undefined : undefined;
+
+type T8 = test extends Echo<string> ?
+// something
+    unknown : test extends number ? undefined :
+    // else
+        undefined;
+
+type T9 = test extends Echo<string>
+    // something
+    ? unknown : test extends number ? undefined :
+        // else
+        undefined;
+
+type T10 =
+    // comment
+    test extends Echo<string> ? test extends number ? unknown : unknown : undefined;

crates/biome_js_formatter/tests/specs/ts/type/conditional.ts.snap

@@ -1,5 +1,6 @@
 ---
 source: crates/biome_formatter_test/src/snapshot_builder.rs
+assertion_line: 211
 info: ts/type/conditional.ts
 ---
 # Input
@@ -22,6 +23,33 @@ type T4 = test extends string
     ? unknown : test extends number ? undefined :
         // else
         undefined;
+
+type T5 =
+    // comment
+    test extends string ? test extends number ? unknown : unknown : undefined;
+
+type Echo<T> = T
+
+type T6 = test extends Echo<string> ? test extends number ? unknown : unknown : undefined;
+
+type T7 = test extends Echo<string> ?  unknown : test extends number ? undefined : undefined;
+
+type T8 = test extends Echo<string> ?
+// something
+    unknown : test extends number ? undefined :
+    // else
+        undefined;
+
+type T9 = test extends Echo<string>
+    // something
+    ? unknown : test extends number ? undefined :
+        // else
+        undefined;
+
+type T10 =
+    // comment
+    test extends Echo<string> ? test extends number ? unknown : unknown : undefined;
+
 ```
 
 
@@ -79,4 +107,50 @@ type T4 = test extends string
 		? undefined
 		: // else
 			undefined;
+
+type T5 =
+	// comment
+	test extends string ? (test extends number ? unknown : unknown) : undefined;
+
+type Echo<T> = T;
+
+type T6 =
+	test extends Echo<string>
+		? test extends number
+			? unknown
+			: unknown
+		: undefined;
+
+type T7 =
+	test extends Echo<string>
+		? unknown
+		: test extends number
+			? undefined
+			: undefined;
+
+type T8 =
+	test extends Echo<string>
+		? // something
+			unknown
+		: test extends number
+			? undefined
+			: // else
+				undefined;
+
+type T9 =
+	test extends Echo<string>
+		? // something
+			unknown
+		: test extends number
+			? undefined
+			: // else
+				undefined;
+
+type T10 =
+	// comment
+	test extends Echo<string>
+		? test extends number
+			? unknown
+			: unknown
+		: undefined;
 ```