Issue 272 implement

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 We follow semantic versioning.
 
+## Version 1.6.0
+
+### Features
+
+- Adds template variables processing
+
 
 ## Version 1.5.0
 

README.md

@@ -116,6 +116,26 @@ VALUE=0
 VAR=foo
 ```
 
+You can use template string.
+
+```bash
+$ cat template.env
+SECRET_ANSWER=42
+SECRET_TOKEN=very secret string
+SECRET_VALUE=0
+SECRET_TEMPLATE=${SECRET_ANSWER}${SECRET_TOKEN}${SECRET_VALUE}
+```
+
+Template string must be below the variables that will fill it.
+
+```bash
+$ dump-env -t .env.template -p SECRET_
+SECRET_ANSWER=42
+SECRET_TEMPLATE=42very secret string0
+SECRET_TOKEN=very secret string
+SECRET_VALUE=0
+
+```
 #### Strict Source
 
 Using the `--strict-source` flag has the same effect as defining a `--strict` flag for every variable defined in the source template.

dump_env/cli.py

@@ -40,6 +40,11 @@ def _create_parser() -> argparse.ArgumentParser:
         action='store_true',
         help='All source template variables should exist in os envs',
     )
+    parser.add_argument(
+        '--fill',
+        action='store_true',
+        help='Fill variables in .env.template file',
+    )
     return parser
 
 
@@ -95,6 +100,14 @@ def main() -> NoReturn:
 
             $ dump-env -s .env.template --strict-source
 
+        This example will fill all variables keys in the source template
+        from variables in this template file:
+
+        .. code:: bash
+
+            $ dump-env -s .env.template --fill
+
+
     """
     args = _create_parser().parse_args()
     strict_vars = set(args.strict) if args.strict else None
@@ -106,6 +119,7 @@ def main() -> NoReturn:
             strict_vars,
             args.source,
             args.strict_source,
+            args.fill,
         )
     except StrictEnvError as exc:
         sys.stderr.write('{0}\n'.format(str(exc)))

dump_env/dumper.py

@@ -7,6 +7,7 @@
 Store = Mapping[str, str]
 
 EMPTY_STRING: Final = ''
+VAR_TEMPLATE: Final = r'\${([a-zA-Z_]+)}'
 
 
 def _parse(source: str) -> Store:
@@ -20,7 +21,7 @@ def _parse(source: str) -> Store:
         Store with all keys and values.
 
     """
-    parsed_data = {}
+    parsed_data: Dict[str, str] = {}
 
     with open(source) as env_file:
         for line in env_file:
@@ -35,7 +36,6 @@ def _parse(source: str) -> Store:
             env_name = env_name.strip()
             env_value = env_value.strip().strip('\'"')
             parsed_data[env_name] = env_value
-
     return parsed_data
 
 
@@ -98,12 +98,58 @@ def _source(source: str, strict_source: bool) -> Store:
     return sourced
 
 
-def dump(
+def _parse_variable_names(template_var: str) -> List[str]:
+    """Parse variables from template string."""
+    names = []
+    name_begin_idx: int = -1
+    name_end_idx: int = -1
+    for idx in range(len(template_var) - 1):
+        if template_var[idx] == '$' and template_var[idx + 1] == '{':
+            name_begin_idx = idx + 2
+        if template_var[idx + 1] == '}':
+            name_end_idx = idx + 1
+        if name_begin_idx < name_end_idx:
+            names.append(template_var[name_begin_idx: name_end_idx])
+            name_begin_idx = -1
+            name_end_idx = -1
+    return names
+
+
+def _fill(
+    store: Dict[str, str],
+) -> Dict[str, str]:
+    """
+    Fill template env var if all vars has in store.
+
+    Args:
+        store: Store of env variables
+
+    Returns:
+        Filled store
+
+    """
+    for key, env_value in store.items():
+        if '${' in env_value and '}' in env_value:
+            variables = _parse_variable_names(env_value)
+            form = {
+                env_variable: store.get(env_variable)
+                for env_variable in variables
+                if store.get(env_variable) is not None
+            }
+            if form and len(form.keys()) == len(variables):
+                filled_value = env_value.format(**form)
+                filled_value = filled_value.replace('$', '')
+                store[key] = filled_value
+    return store
+
+
+def dump(  # noqa: WPS211, C901
     template: str = EMPTY_STRING,
     prefixes: Optional[List[str]] = None,
     strict_keys: Optional[Set[str]] = None,
     source: str = EMPTY_STRING,
     strict_source: bool = False,
+    fill: bool = False,
 ) -> Dict[str, str]:
     """
     This function is used to dump ``.env`` files.
@@ -129,6 +175,8 @@ def dump(
         strict_source: Whether all keys in source template must also be
            presented in env vars.
 
+        fill: Fill all variables in template env file.
+
     Returns:
         Ordered key-value pairs of dumped env and template variables.
 
@@ -156,5 +204,7 @@ def dump(
     for prefix in prefixes:
         store.update(_preload_existing_vars(prefix))
 
+    if fill:
+        store.update(_fill(store))
     # Sort keys and keep them ordered:
     return OrderedDict(sorted(store.items()))