Python: Add QL support for lazy imports

Adds a new `isLazy` predicate to the relevant classes, and adds the
relevant dbscheme (and up/downgrade) changes. On upgrades we do nothing,
and on downgrades we remove the `is_lazy` bits.

python/ql/lib/semmle/python/AstGenerated.qll

@@ -698,6 +698,9 @@ class Import_ extends @py_Import, Stmt {
   /** Gets an alias of this import statement. */
   Alias getAName() { result = this.getNames().getAnItem() }
 
+  /** Whether the lazy property of this import statement is true. */
+  predicate isLazy() { py_bools(this, 2) }
+
   override string toString() { result = "Import" }
 }
 
@@ -720,6 +723,9 @@ class ImportStar_ extends @py_ImportStar, Stmt {
   /** Gets the module of this import * statement. */
   Expr getModule() { py_exprs(result, _, this, 1) }
 
+  /** Whether the lazy property of this import * statement is true. */
+  predicate isLazy() { py_bools(this, 2) }
+
   override string toString() { result = "ImportStar" }
 }
 

python/ql/lib/semmlecode.python.dbscheme

@@ -517,6 +517,7 @@ py_extracted_version(int module : @py_Module ref,
 
 /* <Field> Import.location = 0, location */
 /* <Field> Import.names = 1, alias_list */
+/* <Field> Import.is_lazy = 2, bool */
 
 /* <Field> ImportExpr.location = 0, location */
 /* <Field> ImportExpr.parenthesised = 1, bool */
@@ -526,6 +527,7 @@ py_extracted_version(int module : @py_Module ref,
 
 /* <Field> ImportStar.location = 0, location */
 /* <Field> ImportStar.module = 1, expr */
+/* <Field> ImportStar.is_lazy = 2, bool */
 
 /* <Field> ImportMember.location = 0, location */
 /* <Field> ImportMember.parenthesised = 1, bool */
@@ -1127,7 +1129,7 @@ case @py_unaryop.kind of
 
 @py_ast_node = @py_Class | @py_Function | @py_Module | @py_StringPart | @py_comprehension | @py_dict_item | @py_expr | @py_pattern | @py_stmt | @py_type_parameter;
 
-@py_bool_parent = @py_For | @py_Function | @py_Print | @py_With | @py_expr | @py_pattern;
+@py_bool_parent = @py_For | @py_Function | @py_Import | @py_ImportStar | @py_Print | @py_With | @py_expr | @py_pattern;
 
 @py_dict_item_list_parent = @py_Call | @py_ClassExpr | @py_Dict;
 

python/ql/lib/upgrades/279cbb08d387ecd57ac177e87c94cfd5ca62f792/upgrade.properties

@@ -0,0 +1,2 @@
+description: Add is_lazy field to Import and ImportStar for PEP 810 lazy imports
+compatibility: backwards