refactor: improve import namespace handling

CHANGELOG.md

@@ -45,6 +45,31 @@ our [guidelines for writing a good changelog entry](https://github.com/biomejs/b
 
 #### Bug fixes
 
+- [noUndeclaredVariables](https://biomejs.dev/linter/rules/no-undeclared-variables/) and [noUnusedImports](https://biomejs.dev/linter/rules/no-unused-imports) now correctly handle import namespaces ([#2796](https://github.com/biomejs/biome/issues/2796)).
+
+  Previously, Biome bound unqualified type to import namespaces.
+  Import namespaces can only be used as qualified names in a type (ambient) context.
+
+  ```ts
+  // Unused import
+  import * as Ns1 from "";
+  // This doesn't reference the import namespace `Ns1`
+  type T1 = Ns1; // Undeclared variable `Ns1`
+
+  // Unused import
+  import type * as Ns2 from "";
+  // This doesn't reference the import namespace `Ns2`
+  type T2 = Ns2; // Undeclared variable `Ns2`
+
+  import type * as Ns3 from "";
+  // This references the import namespace because it is a qualified name.
+  type T3 = Ns3.Inner;
+  // This also references the import namespace.
+  export type { Ns3 }
+  ```
+
+  Contributed by @Conaclos
+
 - `useJsxKeyInIterable` now handles more cases involving fragments. See the snippets below. Contributed by @dyc3
 ```jsx
 // valid

crates/biome_js_analyze/tests/specs/correctness/noUndeclaredVariables/invalidNamesapceReference.ts

@@ -0,0 +1,5 @@
+import * as Ns1 from "";
+export type T1 = Ns1; // This doesn't reference the import namespace `Ns1`
+
+import type * as Ns2 from "";
+export type T2 = Ns2;  // This doesn't reference the import namespace `Ns1`

crates/biome_js_analyze/tests/specs/correctness/noUndeclaredVariables/invalidNamesapceReference.ts.snap

@@ -0,0 +1,39 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: invalidNamesapceReference.ts
+---
+# Input
+```ts
+import * as Ns1 from "";
+export type T1 = Ns1; // This doesn't reference the import namespace `Ns1`
+
+import type * as Ns2 from "";
+export type T2 = Ns2;  // This doesn't reference the import namespace `Ns1`
+```
+
+# Diagnostics
+```
+invalidNamesapceReference.ts:2:18 lint/correctness/noUndeclaredVariables ━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! The Ns1 variable is undeclared
+  
+    1 │ import * as Ns1 from "";
+  > 2 │ export type T1 = Ns1; // This doesn't reference the import namespace `Ns1`
+      │                  ^^^
+    3 │ 
+    4 │ import type * as Ns2 from "";
+  
+
+```
+
+```
+invalidNamesapceReference.ts:5:18 lint/correctness/noUndeclaredVariables ━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! The Ns2 variable is undeclared
+  
+    4 │ import type * as Ns2 from "";
+  > 5 │ export type T2 = Ns2;  // This doesn't reference the import namespace `Ns1`
+      │                  ^^^
+  
+
+```

crates/biome_js_analyze/tests/specs/correctness/noUnusedImports/invalid-import-namespace.ts

@@ -0,0 +1,5 @@
+import * as Ns1 from ""
+export type T1 = Ns1;
+
+import type * as Ns2 from ""
+export type T2 = Ns2;

crates/biome_js_analyze/tests/specs/correctness/noUnusedImports/invalid-import-namespace.ts.snap

@@ -0,0 +1,56 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: invalid-import-namespace.ts
+---
+# Input
+```ts
+import * as Ns1 from ""
+export type T1 = Ns1;
+
+import type * as Ns2 from ""
+export type T2 = Ns2;
+```
+
+# Diagnostics
+```
+invalid-import-namespace.ts:1:13 lint/correctness/noUnusedImports  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! This import is unused.
+  
+  > 1 │ import * as Ns1 from ""
+      │             ^^^
+    2 │ export type T1 = Ns1;
+    3 │ 
+  
+  i Unused imports might be the result of an incomplete refactoring.
+  
+  i Safe fix: Remove the unused import.
+  
+    1 │ import·*·as·Ns1·from·""
+      │ -----------------------
+
+```
+
+```
+invalid-import-namespace.ts:4:18 lint/correctness/noUnusedImports  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! This import is unused.
+  
+    2 │ export type T1 = Ns1;
+    3 │ 
+  > 4 │ import type * as Ns2 from ""
+      │                  ^^^
+    5 │ export type T2 = Ns2;
+  
+  i Unused imports might be the result of an incomplete refactoring.
+  
+  i Safe fix: Remove the unused import.
+  
+    1 1 │   import * as Ns1 from ""
+    2 2 │   export type T1 = Ns1;
+    3   │ - 
+    4   │ - import·type·*·as·Ns2·from·""
+    5 3 │   export type T2 = Ns2;
+  
+
+```

crates/biome_js_analyze/tests/specs/correctness/noUnusedVariables/validNamesapceExportType.ts

@@ -0,0 +1,2 @@
+namespace Ns {}
+export type { Ns }

crates/biome_js_analyze/tests/specs/correctness/noUnusedVariables/validNamesapceExportType.ts.snap

@@ -0,0 +1,9 @@
+---
+source: crates/biome_js_analyze/tests/spec_tests.rs
+expression: validNamesapceExportType.ts
+---
+# Input
+```ts
+namespace Ns {}
+export type { Ns }
+```

crates/biome_js_analyze/tests/specs/style/useExportType/valid.ts

@@ -38,4 +38,7 @@ export type { f2, Class2, typeNs };
 declare class AmbientClass {}
 declare enum AmbientEnum {}
 declare class AmbientFunction {}
-export { AmbientClass, AmbientEnum, AmbientFunction }
+export { AmbientClass, AmbientEnum, AmbientFunction }
+
+import type * as Ns from ""
+export { Ns }

crates/biome_js_analyze/tests/specs/style/useExportType/valid.ts.snap

@@ -45,6 +45,26 @@ declare class AmbientClass {}
 declare enum AmbientEnum {}
 declare class AmbientFunction {}
 export { AmbientClass, AmbientEnum, AmbientFunction }
+
+import type * as Ns from ""
+export { Ns }
+```
+
+# Diagnostics
 ```
+valid.ts:44:8 lint/style/useExportType  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
 
+  ! All exports are only types and should thus use export type.
+  
+    43 │ import type * as Ns from ""
+  > 44 │ export { Ns }
+       │        ^^^^^^
+  
+  i Using export type allows transpilers to safely drop exports of types without looking for their definition.
+  
+  i Safe fix: Use a grouped export type.
+  
+    44 │ export·type·{·Ns·}
+       │        +++++      
 
+```

crates/biome_js_analyze/tests/specs/suspicious/noRedeclare/invalid.ts

@@ -9,4 +9,10 @@ function f<T, T>() {}
 
 function g<T>() {
     type T = number;
-}
+}
+
+import * as Ns1 from ""
+namespace Ns1 {}
+
+import type * as Ns2 from ""
+namespace Ns2 {}

crates/biome_js_analyze/tests/specs/suspicious/noRedeclare/invalid.ts.snap

@@ -16,6 +16,13 @@ function f<T, T>() {}
 function g<T>() {
     type T = number;
 }
+
+import * as Ns1 from ""
+namespace Ns1 {}
+
+import type * as Ns2 from ""
+namespace Ns2 {}
+
 ```
 
 # Diagnostics
@@ -76,6 +83,7 @@ invalid.ts:11:10 lint/suspicious/noRedeclare ━━━━━━━━━━━
   > 11 │     type T = number;
        │          ^
     12 │ }
+    13 │ 
   
   i 'T' is defined here:
   
@@ -88,3 +96,48 @@ invalid.ts:11:10 lint/suspicious/noRedeclare ━━━━━━━━━━━
   
 
 ```
+
+```
+invalid.ts:15:11 lint/suspicious/noRedeclare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Shouldn't redeclare 'Ns1'. Consider to delete it or rename it.
+  
+    14 │ import * as Ns1 from ""
+  > 15 │ namespace Ns1 {}
+       │           ^^^
+    16 │ 
+    17 │ import type * as Ns2 from ""
+  
+  i 'Ns1' is defined here:
+  
+    12 │ }
+    13 │ 
+  > 14 │ import * as Ns1 from ""
+       │             ^^^
+    15 │ namespace Ns1 {}
+    16 │ 
+  
+
+```
+
+```
+invalid.ts:18:11 lint/suspicious/noRedeclare ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+
+  ! Shouldn't redeclare 'Ns2'. Consider to delete it or rename it.
+  
+    17 │ import type * as Ns2 from ""
+  > 18 │ namespace Ns2 {}
+       │           ^^^
+    19 │ 
+  
+  i 'Ns2' is defined here:
+  
+    15 │ namespace Ns1 {}
+    16 │ 
+  > 17 │ import type * as Ns2 from ""
+       │                  ^^^
+    18 │ namespace Ns2 {}
+    19 │ 
+  
+
+```