Add memoization

README.md

@@ -166,7 +166,7 @@ You can control the user agent that Bazelisk sends in all HTTP requests by setti
 
 # .bazeliskrc configuration file
 
-A `.bazeliskrc` file in the root directory of a workspace or the user home directory allows users to set environment variables persistently.
+A `.bazeliskrc` file in the root directory of a workspace or the user home directory allows users to set environment variables persistently. (The Python implementation of Bazelisk doesn't check the user home directory yet, only the workspace directory.)
 
 Example file content:
 

bazelisk.py

@@ -67,13 +67,22 @@
 
 BAZEL_UPSTREAM = "bazelbuild"
 
+_dotfiles_dict = None
 
-def get_env_or_config(name, default=None):
-    """Reads a configuration value from the environment, but falls back to
-    reading it from .bazeliskrc in the workspace root."""
-    if name in os.environ:
-        return os.environ[name]
+
+def get_dotfiles_dict():
+    """Loads all supported dotfiles and returns a unified name=value dictionary
+    for their config settings. The dictionary is only loaded on the first call
+    to this function; subsequent calls used a cached result, so won't change.
+    """
+    global _dotfiles_dict
+    if _dotfiles_dict is not None:
+        return _dotfiles_dict
+    _dotfiles_dict = dict()
     env_files = []
+    # Here we're only checking the workspace root. Ideally, we would also check
+    # the user's home directory to match the Go version. When making that edit,
+    # be sure to obey the correctly prioritization of workspace / home rcfiles.
     root = find_workspace_root()
     if root:
         env_files.append(os.path.join(root, ".bazeliskrc"))
@@ -88,8 +97,18 @@ def get_env_or_config(name, default=None):
             if not line:
                 continue
             some_name, some_value = line.split("=", 1)
-            if some_name == name:
-                return some_value
+            _dotfiles_dict[some_name] = some_value
+    return _dotfiles_dict
+
+
+def get_env_or_config(name, default=None):
+    """Reads a configuration value from the environment, but falls back to
+    reading it from .bazeliskrc in the workspace root."""
+    if name in os.environ:
+        return os.environ[name]
+    dotfiles = get_dotfiles_dict()
+    if name in dotfiles:
+        return dotfiles[name]
     return default