feat(modules.constructFiles): auto-sanitize .key value to always be valid

lib/lib.nix

@@ -682,6 +682,44 @@ in
   */
   toKdl = import ./toKdl.nix { inherit lib wlib; };
 
+  /**
+    Sanitize a string into a valid environment variable name.
+
+    This function sanitizes all characters that are not allowed in typical
+    POSIX environment variable names (`[A-Za-z0-9_]`), and ensures the
+    resulting string starts with a valid leading character (`[A-Za-z_]`).
+
+    Behavior:
+    - All invalid characters are replaced with underscore characters (`_`)
+
+    Examples:
+    ```
+      sanitizeEnvVarName "FOO-BAR"     => "FOO_BAR"
+      sanitizeEnvVarName "123.abc"      => "_23_abc"
+      sanitizeEnvVarName "!@#"         => "___"
+      sanitizeEnvVarName "hello, world!" => "hello__world_"
+    ```
+
+    Notes:
+    - Only ASCII characters are considered; all other characters are removed
+    - This does not guarantee uniqueness across multiple inputs
+  */
+  sanitizeEnvVarName =
+    s:
+    let
+      isUpper = c: c >= "A" && c <= "Z";
+      isLower = c: c >= "a" && c <= "z";
+      isDigit = c: c >= "0" && c <= "9";
+
+      valid =
+        i: c:
+        if i == 0 then
+          isUpper c || isLower c || c == "_"
+        else
+          isUpper c || isLower c || isDigit c || c == "_";
+    in
+    lib.concatStrings (lib.imap0 (i: c: if valid i c then c else "_") (lib.stringToCharacters s));
+
   /**
     Placeholder value used when overriding a non-main field of a spec type.
 

modules/constructFiles/module.nix

@@ -36,6 +36,7 @@
                 then that means you should set this value
                 to something which is a valid shell variable name.
               '';
+              apply = wlib.sanitizeEnvVarName;
             };
             content = lib.mkOption {
               type = lib.types.lines;
@@ -85,16 +86,36 @@
   config.drv = lib.mkIf (config.constructFiles != { }) (
     let
       files = builtins.attrValues config.constructFiles;
+      mkUnique =
+        attrs: base:
+        let
+          try =
+            i:
+            let
+              candidate = if i == null then base else "${base}_${toString i}";
+            in
+            if attrs ? ${candidate} then try (if i == null then 0 else i + 1) else candidate;
+        in
+        try null;
       result =
         builtins.foldl'
-          (acc: v: {
-            attrs = acc.attrs // {
-              ${v.key} = v.content;
-            };
-            passAsFile = acc.passAsFile ++ [ v.key ];
-          })
+          (
+            acc: v:
+            let
+              key = mkUnique acc.attrs v.key;
+            in
+            {
+              attrs = acc.attrs // {
+                ${key} = v.content;
+              };
+              passAsFile = acc.passAsFile ++ [ key ];
+            }
+          )
           {
-            attrs = { };
+            attrs = {
+              # prevents something from being named this
+              passAsFile = [ ];
+            };
             passAsFile = [ ];
           }
           files;