Swift: generate getParent implementation

By explicitly marking children in the `schema.yml` file, an internal
`getAChild` predicate is implemented, that is in turn used in `AstNode`
to implement `getParent`.

This is yet to be used in the control flow library to replace the
hand-rolled implementation.

A further, more complex step is to use the same information to fully
generate the core implementation of `PrintAst` (including the
accessor string). This will be done later.

The `parent` tests use the same swift code as the extractor tests, and
this is currently enforced by `sync-files.py`. Notice that `qltest.sh`
had to be modified to deal with multiple files, which was not working
yet.

Author: redsun82

.pre-commit-config.yaml

@@ -25,7 +25,7 @@ repos:
 
       - id: sync-files
         name: Fix files required to be identical
-        files: \.(qll?|qhelp)$
+        files: \.(qll?|qhelp|swift)$
         language: system
         entry: python3 config/sync-files.py --latest
         pass_filenames: false

config/identical-files.json

@@ -566,5 +566,21 @@
   "Typo database": [
     "javascript/ql/src/Expressions/TypoDatabase.qll",
     "ql/ql/src/codeql_ql/style/TypoDatabase.qll"
+  ],
+  "Swift declarations test file": [
+    "swift/ql/test/extractor-tests/declarations/declarations.swift",
+    "swift/ql/test/library-tests/parent/declarations.swift"
+  ],
+  "Swift statements test file": [
+    "swift/ql/test/extractor-tests/statements/statements.swift",
+    "swift/ql/test/library-tests/parent/statements.swift"
+  ],
+  "Swift expressions test file": [
+    "swift/ql/test/extractor-tests/expressions/expressions.swift",
+    "swift/ql/test/library-tests/parent/expressions.swift"
+  ],
+  "Swift patterns test file": [
+    "swift/ql/test/extractor-tests/patterns/patterns.swift",
+    "swift/ql/test/library-tests/parent/patterns.swift"
   ]
-}
+}

swift/codegen/generators/qlgen.py

@@ -19,6 +19,7 @@ def get_ql_property(cls: schema.Class, prop: schema.Property):
             type=prop.type,
             tablename=inflection.tableize(cls.name),
             tableparams=["this"] + ["result" if p is prop else "_" for p in cls.properties if p.is_single],
+            is_child=prop.is_child,
         )
     elif prop.is_repeated:
         return ql.Property(
@@ -28,6 +29,7 @@ def get_ql_property(cls: schema.Class, prop: schema.Property):
             tablename=inflection.tableize(f"{cls.name}_{prop.name}"),
             tableparams=["this", "index", "result"],
             is_optional=prop.is_optional,
+            is_child=prop.is_child,
         )
     elif prop.is_optional:
         return ql.Property(
@@ -36,6 +38,7 @@ def get_ql_property(cls: schema.Class, prop: schema.Property):
             tablename=inflection.tableize(f"{cls.name}_{prop.name}"),
             tableparams=["this", "result"],
             is_optional=True,
+            is_child=prop.is_child,
         )
     elif prop.is_predicate:
         return ql.Property(

swift/codegen/lib/ql.py

@@ -22,6 +22,7 @@ class Property:
     local_var: str = "x"
     is_optional: bool = False
     is_predicate: bool = False
+    is_child: bool = False
 
     def __post_init__(self):
         if self.tableparams:

swift/codegen/lib/schema.py

@@ -19,6 +19,7 @@ class Property:
 
     name: str
     type: str = None
+    is_child: bool = False
 
 
 @dataclass
@@ -62,17 +63,18 @@ class Schema:
     includes: Set[str] = field(default_factory=set)
 
 
-def _parse_property(name, type):
+def _parse_property(name: str, type: str, is_child: bool = False):
+    assert not (is_child and type[0].islower()), f"children must have class type, got {type} for {name}"
     if type.endswith("?*"):
-        return RepeatedOptionalProperty(name, type[:-2])
+        return RepeatedOptionalProperty(name, type[:-2], is_child=is_child)
     elif type.endswith("*"):
-        return RepeatedProperty(name, type[:-1])
+        return RepeatedProperty(name, type[:-1], is_child=is_child)
     elif type.endswith("?"):
-        return OptionalProperty(name, type[:-1])
+        return OptionalProperty(name, type[:-1], is_child=is_child)
     elif type == "predicate":
         return PredicateProperty(name)
     else:
-        return SingleProperty(name, type)
+        return SingleProperty(name, type, is_child=is_child)
 
 
 class _DirSelector:
@@ -109,6 +111,8 @@ def load(path):
                     classes[base].derived.add(name)
             elif k == "_dir":
                 cls.dir = pathlib.Path(v)
+            elif k == "_children":
+                cls.properties.extend(_parse_property(kk, vv, is_child=True) for kk, vv in v.items())
         if not cls.bases and cls.name != root_class_name:
             cls.bases.add(root_class_name)
             classes[root_class_name].derived.add(name)