package_hash: remove all unassigned strings, not just docstrings

Some packages use top-level unassigned strings instead of comments, either just after a
docstring on in the body somewhere else. Ignore those strings becasue they have no
effect on package behavior.

- [x] adjust RemoveDocstrings to remove all free-standing strings.
- [x] move tests for util/package_hash.py to test/util/package_hash.py

Co-authored-by: Danny McClanahan <1305167+cosmicexplorer@users.noreply.github.com>

lib/spack/spack/test/util/package_hash.py

@@ -3,18 +3,22 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+import ast
+
+import spack.paths
+import spack.util.package_hash as ph
 from spack.spec import Spec
-from spack.util.package_hash import package_content, package_hash
+from spack.util.unparse import unparse
 
 
 def test_hash(tmpdir, mock_packages, config):
-    package_hash("hash-test1@1.2")
+    ph.package_hash("hash-test1@1.2")
 
 
 def test_different_variants(tmpdir, mock_packages, config):
     spec1 = Spec("hash-test1@1.2 +variantx")
     spec2 = Spec("hash-test1@1.2 +varianty")
-    assert package_hash(spec1) == package_hash(spec2)
+    assert ph.package_hash(spec1) == ph.package_hash(spec2)
 
 
 def test_all_same_but_name(tmpdir, mock_packages, config):
@@ -55,11 +59,67 @@ def test_all_same_but_install(tmpdir, mock_packages, config):
 
 
 def compare_sans_name(eq, spec1, spec2):
-    content1 = package_content(spec1)
+    content1 = ph.package_content(spec1)
     content1 = content1.replace(spec1.package.__class__.__name__, '')
-    content2 = package_content(spec2)
+    content2 = ph.package_content(spec2)
     content2 = content2.replace(spec2.package.__class__.__name__, '')
     if eq:
         assert content1 == content2
     else:
         assert content1 != content2
+
+
+many_strings = '''\
+"""ONE"""
+"""TWO"""
+
+var = "THREE"  # make sure this is not removed
+
+"FOUR"
+
+class ManyDocstrings:
+    """FIVE"""
+    """SIX"""
+
+    x = "SEVEN"
+
+    def method1():
+        """EIGHT"""
+
+        print("NINE")
+
+        "TEN"
+        for i in range(10):
+            print(i)
+
+    def method2():
+        """ELEVEN"""
+        return "TWELVE"
+'''
+
+
+def test_remove_docstrings():
+    tree = ast.parse(many_strings)
+    tree = ph.RemoveDocstrings().visit(tree)
+
+    unparsed = unparse(tree)
+
+    # make sure the methods are preserved
+    assert "method1" in unparsed
+    assert "method2" in unparsed
+
+    # all of these are unassigned and should be removed
+    assert "ONE" not in unparsed
+    assert "TWO" not in unparsed
+    assert "FOUR" not in unparsed
+    assert "FIVE" not in unparsed
+    assert "SIX" not in unparsed
+    assert "EIGHT" not in unparsed
+    assert "TEN" not in unparsed
+    assert "ELEVEN" not in unparsed
+
+    # these are used in legitimate expressions
+    assert "THREE" in unparsed
+    assert "SEVEN" in unparsed
+    assert "NINE" in unparsed
+    assert "TWELVE" in unparsed

lib/spack/spack/util/package_hash.py

@@ -15,12 +15,20 @@
 
 
 class RemoveDocstrings(ast.NodeTransformer):
-    """Transformer that removes docstrings from a Python AST."""
+    """Transformer that removes docstrings from a Python AST.
+
+    This removes *all* strings that aren't on the RHS of an assignment statement from
+    the body of functions, classes, and modules -- even if they're not directly after
+    the declaration.
+
+    """
     def remove_docstring(self, node):
+        def unused_string(node):
+            """Criteria for unassigned body strings."""
+            return isinstance(node, ast.Expr) and isinstance(node.value, ast.Str)
+
         if node.body:
-            if isinstance(node.body[0], ast.Expr) and \
-               isinstance(node.body[0].value, ast.Str):
-                node.body.pop(0)
+            node.body = [child for child in node.body if not unused_string(child)]
 
         self.generic_visit(node)
         return node