package hash: gracefully handle @when with non-string args (#14153)

* when constructing package hash, default to including a method in the content hash if we can't determine whether it would be included by examining the AST
* add a test for updated content-hash calculations
* refactor content hash tests to eliminate repeated lines

var/spack/repos/builtin.mock/packages/hash-test1/package.py

@@ -19,6 +19,9 @@ class HashTest1(Package):
     version('1.2', 'b' * 32)
     version('1.3', 'c' * 32)
     version('1.4', 'd' * 32)
+    version('1.5', 'd' * 32)
+    version('1.6', 'e' * 32)
+    version('1.7', 'f' * 32)
 
     patch('patch1.patch', when="@1.1")
     patch('patch2.patch', when="@1.4")
@@ -34,6 +37,10 @@ def install(self, spec, prefix):
         print("install 1")
         os.listdir(os.getcwd())
 
-    @when('@1.5')
+    @when('@1.5:')
     def install(self, spec, prefix):
         os.listdir(os.getcwd())
+
+    @when('@1.5,1.6')
+    def extra_phase(self, spec, prefix):
+        pass

var/spack/repos/builtin.mock/packages/hash-test3/package.py

@@ -0,0 +1,42 @@
+# Copyright 2013-2019 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack import *
+
+import os
+
+
+class HashTest3(Package):
+    """Used to test package hashing
+    """
+
+    homepage = "http://www.hashtest3.org"
+    url = "http://www.hashtest1.org/downloads/hashtest3-1.1.tar.bz2"
+
+    version('1.2', 'b' * 32)
+    version('1.3', 'c' * 32)
+    version('1.5', 'd' * 32)
+    version('1.6', 'e' * 32)
+    version('1.7', 'f' * 32)
+
+    variant('variantx', default=False, description='Test variant X')
+    variant('varianty', default=False, description='Test variant Y')
+
+    def setup_dependent_environment(self, spack_env, run_env, dependent_spec):
+        pass
+
+    @when('@:1.4')
+    def install(self, spec, prefix):
+        print("install 1")
+        os.listdir(os.getcwd())
+
+    @when('@1.5:')
+    def install(self, spec, prefix):
+        os.listdir(os.getcwd())
+
+    for _version_constraint in ['@1.5', '@1.6']:
+        @when(_version_constraint)
+        def extra_phase(self, spec, prefix):
+            pass