[ty] Improve diagnostics when a submodule is not available as an attribute on a module-literal type

Author: AlexWaygood

crates/ty_python_semantic/resources/mdtest/attributes.md

@@ -2683,6 +2683,39 @@ reveal_type(datetime.UTC)  # revealed: Unknown
 reveal_type(datetime.fakenotreal)  # revealed: Unknown
 ```
 
+## Unimported submodule incorrectly accessed as attribute
+
+We give special diagnostics for this common case too:
+
+<!-- snapshot-diagnostics -->
+
+`foo/__init__.py`:
+
+```py
+```
+
+`foo/bar.py`:
+
+```py
+```
+
+`baz/bar.py`:
+
+```py
+```
+
+`main.py`:
+
+```py
+import foo
+import baz
+
+# error: [unresolved-attribute]
+reveal_type(foo.bar)  # revealed: Unknown
+# error: [unresolved-attribute]
+reveal_type(baz.bar)  # revealed: Unknown
+```
+
 ## References
 
 Some of the tests in the *Class and instance variables* section draw inspiration from

crates/ty_python_semantic/resources/mdtest/import/nonstandard_conventions.md

@@ -60,7 +60,7 @@ Y: int = 47
 import mypackage
 
 reveal_type(mypackage.imported.X)  # revealed: int
-# error: "has no member `fails`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.fails.Y)  # revealed: Unknown
 ```
 
@@ -90,7 +90,7 @@ Y: int = 47
 import mypackage
 
 reveal_type(mypackage.imported.X)  # revealed: int
-# error: "has no member `fails`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.fails.Y)  # revealed: Unknown
 ```
 
@@ -125,7 +125,7 @@ Y: int = 47
 import mypackage
 
 reveal_type(mypackage.imported.X)  # revealed: int
-# error: "has no member `fails`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.fails.Y)  # revealed: Unknown
 ```
 
@@ -155,7 +155,7 @@ Y: int = 47
 import mypackage
 
 reveal_type(mypackage.imported.X)  # revealed: int
-# error: "has no member `fails`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.fails.Y)  # revealed: Unknown
 ```
 
@@ -184,7 +184,7 @@ X: int = 42
 import mypackage
 
 # TODO: this could work and would be nice to have?
-# error: "has no member `imported`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported.X)  # revealed: Unknown
 ```
 
@@ -208,7 +208,7 @@ X: int = 42
 import mypackage
 
 # TODO: this could work and would be nice to have
-# error: "has no member `imported`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported.X)  # revealed: Unknown
 ```
 
@@ -241,15 +241,15 @@ X: int = 42
 ```py
 import mypackage
 
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested.X)  # revealed: Unknown
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.nested)  # revealed: Unknown
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.nested.X)  # revealed: Unknown
 ```
 
@@ -281,9 +281,9 @@ import mypackage
 
 reveal_type(mypackage.submodule)  # revealed: <module 'mypackage.submodule'>
 # TODO: this would be nice to support
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested)  # revealed: Unknown
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested.X)  # revealed: Unknown
 reveal_type(mypackage.nested)  # revealed: <module 'mypackage.submodule.nested'>
 reveal_type(mypackage.nested.X)  # revealed: int
@@ -319,15 +319,15 @@ X: int = 42
 import mypackage
 
 # TODO: this could work and would be nice to have
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested.X)  # revealed: Unknown
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.nested)  # revealed: Unknown
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.nested.X)  # revealed: Unknown
 ```
 
@@ -359,9 +359,9 @@ import mypackage
 
 reveal_type(mypackage.submodule)  # revealed: <module 'mypackage.submodule'>
 # TODO: this would be nice to support
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested)  # revealed: Unknown
-# error: "has no member `nested`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested.X)  # revealed: Unknown
 reveal_type(mypackage.nested)  # revealed: <module 'mypackage.submodule.nested'>
 reveal_type(mypackage.nested.X)  # revealed: int
@@ -396,11 +396,11 @@ X: int = 42
 ```py
 import mypackage
 
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested.X)  # revealed: Unknown
 ```
 
@@ -432,11 +432,11 @@ X: int = 42
 import mypackage
 
 # TODO: this would be nice to support
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested)  # revealed: Unknown
-# error: "has no member `submodule`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.submodule.nested.X)  # revealed: Unknown
 ```
 
@@ -463,9 +463,9 @@ X: int = 42
 ```py
 import mypackage
 
-# error: "has no member `imported`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported.X)  # revealed: Unknown
-# error: "has no member `imported_m`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported_m.X)  # revealed: Unknown
 ```
 
@@ -489,7 +489,7 @@ X: int = 42
 import mypackage
 
 # TODO: this would be nice to support, as it works at runtime
-# error: "has no member `imported`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported.X)  # revealed: Unknown
 reveal_type(mypackage.imported_m.X)  # revealed: int
 ```
@@ -623,7 +623,7 @@ X: int = 42
 ```py
 import mypackage
 
-# error: "no member `imported`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported.X)  # revealed: Unknown
 ```
 
@@ -676,7 +676,7 @@ from mypackage import imported
 # TODO: this would be nice to support, but it's dangerous with available_submodule_attributes
 # for details, see: https://github.com/astral-sh/ty/issues/1488
 reveal_type(imported.X)  # revealed: int
-# error: "has no member `imported`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported.X)  # revealed: Unknown
 ```
 
@@ -699,9 +699,10 @@ X: int = 42
 import mypackage
 from mypackage import imported
 
-# TODO: this would be nice to support, as it works at runtime
 reveal_type(imported.X)  # revealed: int
-# error: "has no member `imported`"
+
+# TODO: this would be nice to support, as it works at runtime
+# error: [unresolved-attribute]
 reveal_type(mypackage.imported.X)  # revealed: Unknown
 ```
 
@@ -737,9 +738,9 @@ import mypackage
 from mypackage import imported
 
 reveal_type(imported.X)  # revealed: int
-# error: "has no member `fails`"
+# error: [unresolved-attribute]
 reveal_type(imported.fails.Y)  # revealed: Unknown
-# error: "has no member `fails`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.fails.Y)  # revealed: Unknown
 ```
 
@@ -772,7 +773,7 @@ from mypackage import imported
 
 reveal_type(imported.X)  # revealed: int
 reveal_type(imported.fails.Y)  # revealed: int
-# error: "has no member `fails`"
+# error: [unresolved-attribute]
 reveal_type(mypackage.fails.Y)  # revealed: Unknown
 ```
 

crates/ty_python_semantic/resources/mdtest/import/relative.md

@@ -247,7 +247,7 @@ X: int = 42
 from . import foo
 import package
 
-# error: [unresolved-attribute] "Module `package` has no member `foo`"
+# error: [unresolved-attribute]
 reveal_type(package.foo.X)  # revealed: Unknown
 ```
 

crates/ty_python_semantic/resources/mdtest/snapshots/attributes.md_-_Attributes_-_Unimported_submodule…_(2b6da09ed380b2).snap

@@ -0,0 +1,68 @@
+---
+source: crates/ty_test/src/lib.rs
+expression: snapshot
+---
+---
+mdtest name: attributes.md - Attributes - Unimported submodule incorrectly accessed as attribute
+mdtest path: crates/ty_python_semantic/resources/mdtest/attributes.md
+---
+
+# Python source files
+
+## foo/__init__.py
+
+```
+```
+
+## foo/bar.py
+
+```
+```
+
+## baz/bar.py
+
+```
+```
+
+## main.py
+
+```
+1 | import foo
+2 | import baz
+3 | 
+4 | # error: [unresolved-attribute]
+5 | reveal_type(foo.bar)  # revealed: Unknown
+6 | # error: [unresolved-attribute]
+7 | reveal_type(baz.bar)  # revealed: Unknown
+```
+
+# Diagnostics
+
+```
+error[unresolved-attribute]: Submodule `bar` may not be available as an attribute on module `foo`
+ --> src/main.py:5:13
+  |
+4 | # error: [unresolved-attribute]
+5 | reveal_type(foo.bar)  # revealed: Unknown
+  |             ^^^^^^^
+6 | # error: [unresolved-attribute]
+7 | reveal_type(baz.bar)  # revealed: Unknown
+  |
+help: Consider explicitly importing `foo.bar`
+info: rule `unresolved-attribute` is enabled by default
+
+```
+
+```
+error[unresolved-attribute]: Submodule `bar` may not be available as an attribute on module `baz`
+ --> src/main.py:7:13
+  |
+5 | reveal_type(foo.bar)  # revealed: Unknown
+6 | # error: [unresolved-attribute]
+7 | reveal_type(baz.bar)  # revealed: Unknown
+  |             ^^^^^^^
+  |
+help: Consider explicitly importing `baz.bar`
+info: rule `unresolved-attribute` is enabled by default
+
+```

crates/ty_python_semantic/resources/mdtest/type_properties/is_equivalent_to.md

@@ -628,7 +628,7 @@ import imported
 from module2 import imported as other_imported
 from ty_extensions import TypeOf, static_assert, is_equivalent_to
 
-# error: [unresolved-attribute] "Module `imported` has no member `abc`"
+# error: [unresolved-attribute]
 reveal_type(imported.abc)  # revealed: Unknown
 
 reveal_type(other_imported.abc)  # revealed: <module 'imported.abc'>

crates/ty_python_semantic/src/types/infer/builder.rs

@@ -9077,10 +9077,30 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
                 }
 
                 let diagnostic = match value_type {
-                    Type::ModuleLiteral(module) => builder.into_diagnostic(format_args!(
-                        "Module `{}` has no member `{attr_name}`",
-                        module.module(db).name(db),
-                    )),
+                    Type::ModuleLiteral(module) => {
+                        let module = module.module(db);
+                        let module_name = module.name(db);
+                        if module.kind(db).is_package()
+                            && let Some(relative_submodule) = ModuleName::new(attr_name)
+                        {
+                            let mut maybe_submodule_name = module_name.clone();
+                            maybe_submodule_name.extend(&relative_submodule);
+                            if resolve_module(db, &maybe_submodule_name).is_some() {
+                                let mut diag = builder.into_diagnostic(format_args!(
+                                    "Submodule `{attr_name}` may not be available as an attribute \
+                                    on module `{module_name}`"
+                                ));
+                                diag.help(format_args!(
+                                    "Consider explicitly importing `{maybe_submodule_name}`"
+                                ));
+                                return fallback();
+                            }
+                        }
+
+                        builder.into_diagnostic(format_args!(
+                            "Module `{module_name}` has no member `{attr_name}`",
+                        ))
+                    }
                     Type::ClassLiteral(class) => builder.into_diagnostic(format_args!(
                         "Class `{}` has no attribute `{attr_name}`",
                         class.name(db),