Revert "Merge pull request #5552 from RasmusWL/revert-import-change"

This reverts commit 49d1937, reversing
changes made to d4877a9.

Author: tausbn

python/ql/src/semmle/python/Files.qll

@@ -72,6 +72,33 @@ class File extends Container {
    * are specified to be extracted.
    */
   string getContents() { file_contents(this, result) }
+
+  /** Holds if this file is likely to get executed directly, and thus act as an entry point for execution. */
+  predicate maybeExecutedDirectly() {
+    // Only consider files in the source code, and not things like the standard library
+    exists(this.getRelativePath()) and
+    (
+      // The file doesn't have the extension `.py` but still contains Python statements
+      not this.getExtension().matches("py%") and
+      exists(Stmt s | s.getLocation().getFile() = this)
+      or
+      // The file contains the usual `if __name__ == '__main__':` construction
+      exists(If i, Name name, StrConst main, Cmpop op |
+        i.getScope().(Module).getFile() = this and
+        op instanceof Eq and
+        i.getTest().(Compare).compares(name, op, main) and
+        name.getId() = "__name__" and
+        main.getText() = "__main__"
+      )
+      or
+      // The file contains a `#!` line referencing the python interpreter
+      exists(Comment c |
+        c.getLocation().getFile() = this and
+        c.getLocation().getStartLine() = 1 and
+        c.getText().regexpMatch("^#! */.*python(2|3)?[ \\\\t]*$")
+      )
+    )
+  }
 }
 
 private predicate occupied_line(File f, int n) {
@@ -121,6 +148,9 @@ class Folder extends Container {
     this.getBaseName().regexpMatch("[^\\d\\W]\\w*") and
     result = this.getParent().getImportRoot(n)
   }
+
+  /** Holds if execution may start in a file in this directory. */
+  predicate mayContainEntryPoint() { any(File f | f.getParent() = this).maybeExecutedDirectly() }
 }
 
 /**

python/ql/src/semmle/python/Module.qll

@@ -204,8 +204,13 @@ private string moduleNameFromBase(Container file) {
 string moduleNameFromFile(Container file) {
   exists(string basename |
     basename = moduleNameFromBase(file) and
-    legalShortName(basename) and
+    legalShortName(basename)
+  |
     result = moduleNameFromFile(file.getParent()) + "." + basename
+    or
+    // If execution can start in the folder containing this module, then we will assume `file` can
+    // be imported as an absolute import, and hence return `basename` as a possible name.
+    file.getParent().(Folder).mayContainEntryPoint() and result = basename
   )
   or
   isPotentialSourcePackage(file) and

python/ql/test/3/library-tests/modules/entry_point/hash_bang/main.py

@@ -0,0 +1,7 @@
+#! /usr/bin/python3
+print(__file__)
+import module
+import package
+import namespace_package
+import namespace_package.namespace_package_main
+print(module.message)

python/ql/test/3/library-tests/modules/entry_point/hash_bang/module.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+message = "Hello world!"

python/ql/test/3/library-tests/modules/entry_point/hash_bang/namespace_package/namespace_package_main.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+import namespace_package.namespace_package_module

python/ql/test/3/library-tests/modules/entry_point/hash_bang/namespace_package/namespace_package_module.py

@@ -0,0 +1 @@
+print(__file__.split("entry_point")[1])

python/ql/test/3/library-tests/modules/entry_point/hash_bang/package/__init__.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+from . import package_main

python/ql/test/3/library-tests/modules/entry_point/hash_bang/package/package_main.py

@@ -0,0 +1,2 @@
+print(__file__.split("entry_point")[1])
+from . import package_module

python/ql/test/3/library-tests/modules/entry_point/hash_bang/package/package_module.py

@@ -0,0 +1 @@
+print(__file__.split("entry_point")[1])

python/ql/test/3/library-tests/modules/entry_point/modules.expected

@@ -0,0 +1,16 @@
+| main | hash_bang/main.py:0:0:0:0 | Script main |
+| main | name_main/main.py:0:0:0:0 | Module main |
+| module | hash_bang/module.py:0:0:0:0 | Module module |
+| module | name_main/module.py:0:0:0:0 | Module module |
+| package | hash_bang/package:0:0:0:0 | Package package |
+| package | name_main/package:0:0:0:0 | Package package |
+| package | no_py_extension/package:0:0:0:0 | Package package |
+| package.__init__ | hash_bang/package/__init__.py:0:0:0:0 | Module package.__init__ |
+| package.__init__ | name_main/package/__init__.py:0:0:0:0 | Module package.__init__ |
+| package.__init__ | no_py_extension/package/__init__.py:0:0:0:0 | Module package.__init__ |
+| package.package_main | hash_bang/package/package_main.py:0:0:0:0 | Module package.package_main |
+| package.package_main | name_main/package/package_main.py:0:0:0:0 | Module package.package_main |
+| package.package_main | no_py_extension/package/package_main.py:0:0:0:0 | Module package.package_main |
+| package.package_module | hash_bang/package/package_module.py:0:0:0:0 | Module package.package_module |
+| package.package_module | name_main/package/package_module.py:0:0:0:0 | Module package.package_module |
+| package.package_module | no_py_extension/package/package_module.py:0:0:0:0 | Module package.package_module |