Adds option for adding a temporary path

CHANGELOG.rst

@@ -9,6 +9,7 @@ This document records the main changes to the sdss_access code.
 3.0.4 (unreleased)
 ------------------
 - Fix issue `52` - rsync failure when remote file is compressed compared to template
+- Issue `48` - Add support for adding temporary paths for use in local sdss_access
 
 3.0.3 (11-29-2023)
 ------------------

python/sdss_access/path/path.py

@@ -1047,6 +1047,60 @@ def url(self, filetype, base_dir=None, sasdir='sas', **kwargs):
                 url = re.sub(r'(/v?[0-9._]+/)', r'/tags\1', url, count=1)
         return url
 
+    def add_temp_path(self, name: str, path: str, envvar_path: str = None):
+        """ Add a temporary path template in sdss_access
+
+        Add a path template temporarily into the local os environment
+        for use in sdss_access.  Define a template name and path.
+        The path must start with an environment variable definition.
+
+        This is useful for development of new paths before adding them to the
+        tree and tagging a new version.  This allows sdss_access to still
+        be used in the interim.  This is an alternative to checking out
+        the tree git repo and modifying paths there.  The recommended way
+        of adding new paths is through a PR on the tree product.
+
+        Parameters
+        ----------
+        name : str
+            the temporary file species name
+        path : str
+            the temporary template directory path
+        envvar_path : str, optional
+            the definition path of the environment variable, by default None
+
+        Raises
+        ------
+        ValueError
+            when the name does not match the correct syntax
+        ValueError
+            when the path does not start with an environment variable
+        ValueError
+            when the environment variable is not defined
+        """
+
+        # check name syntax
+        if not re.match(r"^[a-zA-Z_0-9\-]+$", name):
+            raise ValueError('Name can only consist of letters, numbers, dashes or underscores.')
+
+        # check if template path starts with an environment variable
+        envvar = path.split("/", 1)[0]
+        if not envvar.startswith("$"):
+            raise ValueError('Template path must start with an environment variable, $ENVVAR_NAME.')
+
+        # check envvar is in the local environment
+        if envvar[1:] not in os.environ:
+            if not envvar_path:
+                raise ValueError('Template path envvar not defined in local '
+                                 'environment. Please specify an envvar_path.')
+
+            # add the envvar
+            envvar_path = envvar_path.rstrip("/")
+            os.environ[envvar[1:]] = envvar_path
+
+        # add the temporary path template
+        self.templates[name] = path
+
 
 def _expandvars(template):
     ''' Recursively run os.path.expandvars

tests/path/test_path.py

@@ -361,6 +361,28 @@ def test_fzcomp(self, exist, path, monkeypatch, tmp_path):
         else:
             assert pp.endswith('test.txt.fz')
 
+    @pytest.mark.parametrize('name, temp, envvar, exp',
+                             [('testFile', '$LVM_DATA_S/test_file_{ver}.fits', None, 'sdsswork/data/lvm/lco'),
+                              ('testFile', '$TEST_DIR/test_file_{ver}.fits', '/tmp/test/path/', 'tmp/test/path')],
+                             ids=['withev', 'newev'])
+    def test_add_temp_path(self, path, name, temp, envvar, exp):
+        path.add_temp_path(name, temp, envvar_path=envvar)
+
+        full = path.full(name, ver='1.0')
+        assert full.endswith('test_file_1.0.fits')
+        assert exp in full
+
+
+    @pytest.mark.parametrize('name, temp, msg',
+                        [("testFile!", "/path/to/testfile.fits", 'Name can only consist of letters, numbers, dashes'),
+                         ("testFile", "/path/to/testfile.fits", 'Template path must start with an environment variable'),
+                         ("testFile", "$TEST_DI/testfile.fits", 'Template path envvar not defined in local environment')],
+                        ids=['badname', 'badpath', 'noenvvar'])
+    def test_add_temp_fails(self, path, name, temp, msg):
+        with pytest.raises(ValueError, match=msg):
+            path.add_temp_path(name, temp)
+
+
 @pytest.fixture()
 def monkeyoos(monkeypatch, mocker):
     ''' monkeypatch the original os environ from tree '''