"spack config add": allow values with a ":" (#39279)

If you wanted to set a configuration option like
`config:install_tree:root` to "C:/path/to/config.yaml", Spack  had
trouble parsing this because of the ":" in the value. This adds
logic to allow using quotes to enclose the value, so you can add
`config:install_tree:root:"C:/path/to/config.yaml"`.

Configuration keys should never contain a quote character, so the
presence of any quote is taken to mean that the rest of the string
is specifying the value.

lib/spack/spack/config.py

@@ -863,6 +863,7 @@ def add(fullpath, scope=None):
     has_existing_value = True
     path = ""
     override = False
+    value = syaml.load_config(components[-1])
     for idx, name in enumerate(components[:-1]):
         # First handle double colons in constructing path
         colon = "::" if override else ":" if path else ""
@@ -883,14 +884,14 @@ def add(fullpath, scope=None):
             existing = get_valid_type(path)
 
             # construct value from this point down
-            value = syaml.load_config(components[-1])
             for component in reversed(components[idx + 1 : -1]):
                 value = {component: value}
             break
 
+    if override:
+        path += "::"
+
     if has_existing_value:
-        path, _, value = fullpath.rpartition(":")
-        value = syaml.load_config(value)
         existing = get(path, scope=scope)
 
     # append values to lists
@@ -1231,11 +1232,17 @@ def they_are(t):
     return copy.copy(source)
 
 
-#
-# Process a path argument to config.set() that may contain overrides ('::' or
-# trailing ':')
-#
 def process_config_path(path):
+    """Process a path argument to config.set() that may contain overrides ('::' or
+    trailing ':')
+
+    Note: quoted value path components will be processed as a single value (escaping colons)
+        quoted path components outside of the value will be considered ill formed and will
+        raise.
+        e.g. `this:is:a:path:'value:with:colon'` will yield:
+
+            [this, is, a, path, value:with:colon]
+    """
     result = []
     if path.startswith(":"):
         raise syaml.SpackYAMLError("Illegal leading `:' in path `{0}'".format(path), "")
@@ -1262,6 +1269,16 @@ def process_config_path(path):
             front = syaml.syaml_str(front)
             front.append = True
 
+        quote = "['\"]"
+        not_quote = "[^'\"]"
+
+        if re.match(f"^{quote}", path):
+            m = re.match(rf"^{quote}({not_quote}+){quote}$", path)
+            if not m:
+                raise ValueError("Quotes indicate value, but there are additional path entries")
+            result.append(m.group(1))
+            break
+
         result.append(front)
     return result
 

lib/spack/spack/test/config.py

@@ -277,6 +277,12 @@ def test_add_config_path(mutable_config):
     compilers = spack.config.get("packages")["all"]["compiler"]
     assert "gcc" in compilers
 
+    # Try with an escaped colon
+    path = 'config:install_tree:root:"C:/path/to/config.yaml"'
+    spack.config.add(path)
+    set_value = spack.config.get("config")["install_tree"]["root"]
+    assert set_value == "C:/path/to/config.yaml"
+
 
 @pytest.mark.regression("17543,23259")
 def test_add_config_path_with_enumerated_type(mutable_config):