From 2d3ab680aa637c24642124f6ff102cff22ebc774 Mon Sep 17 00:00:00 2001
From: Allison Thackston <allison@allisonthackston.com>
Date: Mon, 16 Mar 2026 12:24:54 -0700
Subject: [PATCH] Don't overwrite config keys if they already exist

---
 mkdocs_simple_plugin/generator.py | 18 ++++++++++---
 tests/test_generator.py           | 43 +++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/mkdocs_simple_plugin/generator.py b/mkdocs_simple_plugin/generator.py
index 7d3302e15..eaf2e32db 100644
--- a/mkdocs_simple_plugin/generator.py
+++ b/mkdocs_simple_plugin/generator.py
@@ -53,24 +53,31 @@ def default_config():
     # Set the default edit uri to empty since doc files are built from source
     # and may not exist.
     config['edit_uri'] = ''
+    return config
+
+
+def apply_environment_config(config, existing_config=None):
+    """Set config values from the environment unless already in the file."""
+    existing_config = existing_config or {}
 
     def maybe_set_string(name):
         env_variable = "INPUT_" + name.upper()
         config_variable = name.lower()
-        if os.environ.get(env_variable):
+        config_exists = config_variable in existing_config
+        if os.environ.get(env_variable) and not config_exists:
             config[config_variable] = os.environ[env_variable]
 
     def maybe_set_dict(name, key):
         env_variable = "INPUT_" + name.upper()
         config_variable = name.lower()
-        if os.environ.get(env_variable):
+        config_exists = config_variable in existing_config
+        if os.environ.get(env_variable) and not config_exists:
             config[config_variable] = {key: os.environ[env_variable]}
-    # Set the config variables via environment if exist
+
     maybe_set_string("site_name")
     maybe_set_string("site_url")
     maybe_set_string("repo_url")
     maybe_set_dict("theme", "name")
-    return config
 
 
 class MkdocsConfigDumper(yaml.Dumper):
@@ -100,9 +107,11 @@ def write_config(config_file, config):
 def setup_config(config_file="mkdocs.yml"):
     """Create the mkdocs.yml file with defaults for params that don't exist."""
     config = default_config()
+    local_config = {}
     if not os.path.exists(config_file):
         # If config file doesn't exit, create a simple one, guess the site name
         # from the folder name.
+        apply_environment_config(config)
         write_config(config_file, config)
     # Open the config file to verify settings.
     with open(config_file, 'r', encoding="utf-8") as stream:
@@ -112,6 +121,7 @@ def setup_config(config_file="mkdocs.yml"):
                 # Overwrite default config values with local mkdocs.yml
                 config.update(local_config)
                 print(config)
+            apply_environment_config(config, local_config)
             if not os.path.exists(config["docs_dir"]):
                 #  Ensure docs directory exists.
                 print("making docs_dir %s", config["docs_dir"])
diff --git a/tests/test_generator.py b/tests/test_generator.py
index df06e56b1..879989531 100755
--- a/tests/test_generator.py
+++ b/tests/test_generator.py
@@ -6,6 +6,7 @@
 
 from mkdocs import theme
 from mkdocs.config import defaults
+import yaml
 
 from mkdocs_simple_plugin import generator
 
@@ -106,6 +107,48 @@ def test_theme(self):
             config_value={"name": "readthedocs"},
             loaded_type=theme.Theme)
 
+    def test_existing_site_name_is_not_overwritten_by_env(self):
+        """Test that an existing site name in mkdocs.yml is preserved."""
+        os.environ["INPUT_SITE_NAME"] = "from-env"
+        generator.write_config(
+            self.test_mkdocs_filename,
+            {
+                "site_name": "from-file",
+                "docs_dir": tempfile.mkdtemp(),
+                "plugins": ("simple", "search"),
+                "edit_uri": "",
+            })
+
+        test_config = generator.setup_config(self.test_mkdocs_filename)
+
+        self.assertEqual(test_config["site_name"], "from-file")
+        with open(self.test_mkdocs_filename, 'r', encoding="utf-8") as stream:
+            written_config = yaml.load(stream, yaml.Loader)
+        self.assertEqual(written_config["site_name"], "from-file")
+
+    def test_existing_theme_is_not_overwritten_by_env(self):
+        """Test that an existing theme in mkdocs.yml is preserved."""
+        os.environ["INPUT_THEME"] = "readthedocs"
+        generator.write_config(
+            self.test_mkdocs_filename,
+            {
+                "site_name": "from-file",
+                "docs_dir": tempfile.mkdtemp(),
+                "plugins": ("simple", "search"),
+                "edit_uri": "",
+                "theme": {"name": "mkdocs"},
+            })
+
+        test_config = generator.setup_config(self.test_mkdocs_filename)
+
+        self.assertEqual(test_config["theme"], {"name": "mkdocs"})
+        cfg = defaults.MkDocsConfig()
+        cfg.load_dict(test_config)
+        errors, warnings = cfg.validate()
+        self.assertEqual(len(errors), 0, errors)
+        self.assertEqual(len(warnings), 0, warnings)
+        self.assertIsInstance(cfg["theme"], theme.Theme)
+
 
 if __name__ == '__main__':
     unittest.main()