Implements new value_to functionality

docs/content/definition-attributes/value-to.md

@@ -0,0 +1,34 @@
+# value_to
+
+The `value_to` definition-attribute makes it possible to send the generated `value` to either STDOUT or STDERR.
+
+This can be helpful in circumstances when a quick debug reveal is required or you need to provide some kind of 
+user response.
+
+
+### Example - to STDERR
+
+```yaml
+env-alias:
+
+  EXAMPLE_STDERR:
+    name: null
+    value: "This is a message that will get sent to STDERR"
+    value_to: "<STDERR>"
+```
+
+
+### Example - to STDOUT
+
+```yaml
+env-alias:
+
+  EXAMPLE_STDOUT_CONTENT:
+    name: null
+    exec: "date"
+
+  EXAMPLE_STDOUT:
+    name: null
+    exec: 'echo "The date is ${EXAMPLE_STDOUT_CONTENT} - boom!"'
+    value_to: "<STDOUT>"
+```

docs/content/examples/terraform-aws-project.md

@@ -16,8 +16,8 @@ values are contained within.
 env-alias:
 
     TF_PLUGIN_CACHE_DIR_CREATE:
+        name: null
         exec: 'mkdir -p ~/.terraform.d/plugin-cache'
-        name: none
 
     TF_PLUGIN_CACHE_DIR:
         value: '~/.terraform.d/plugin-cache'

docs/mkdocs.yml

@@ -12,6 +12,7 @@ nav:
     - definition-attributes/selector.md
     - definition-attributes/name.md
     - definition-attributes/value.md
+    - definition-attributes/value-to.md
     - definition-attributes/exec.md
     - definition-attributes/override.md
     - definition-attributes/keepass-password.md

src/env_alias/lib/generator.py

@@ -41,6 +41,14 @@ def generate(self) -> None:
                 self.values_generated[definition.name] = value
                 os.environ[definition.name] = str(value)  # exists at this process and sub-process only
 
+                if definition.value_to:
+                    if definition.value_to == "<stderr>":
+                        print(value, file=sys.stderr)
+                    elif definition.value_to == "<stdout>":
+                        print(value, file=sys.stdout)
+                    else:
+                        raise EnvAliasException("Unsupported 'value_to' value encountered.")
+
                 if definition._is_internal_only is True:
                     logger.debug(
                         f"Definition for {definition.name!r} defines a 'null' name for env-alias internal "

src/env_alias/models/envalias_definition.py

@@ -21,6 +21,7 @@ class EnvAliasDefinition:
 
     parser: Union[str, None] = None
     selector: Union[str, None] = _UNSET_SENTINEL
+    value_to: Union[str, None] = None
 
     keepass_password: Union[str, None] = None
     ansible_vault_password: Union[str, None] = None
@@ -39,6 +40,11 @@ def __post_init__(self) -> None:
         if not self.source and not self.exec and not self.value and not self.ansible_vault_password_file:
             raise EnvAliasException(f"Must have one 'source', 'exec' or 'value' {_EXCEPTION_END}")
 
+        if isinstance(self.value_to, str):
+            self.value_to = self.value_to.lower()
+            if self.value_to not in ("<stderr>", "<stdout>"):
+                raise EnvAliasException(f"Invalid 'value_to' value, must be '<stderr>' or '<stdout>' {_EXCEPTION_END}")
+
         if self.keepass_password and self.ansible_vault_password:
             raise EnvAliasException(f"Cannot use both 'keepass_password' and 'ansible_vault_password' {_EXCEPTION_END}")
         if self.ansible_vault_password_file and (self.exec or self.source or self.value or self.keepass_password):

tests/test_value_to.py

@@ -0,0 +1,75 @@
+import os
+import random
+import string
+import tempfile
+from pathlib import Path
+
+from env_alias.lib.generator import EnvAliasGenerator
+
+
+def test_value_to_stderr_01(capsys):
+    sentinal = "XXXX_foobar01_XXXX"
+    yaml = f"""
+        EXAMPLE:
+            name: null
+            value: "{sentinal}"
+            value_to: "<stderr>"
+    """
+
+    config_file = __generate_config_file(yaml)
+    EnvAliasGenerator(config_file=config_file).generate()
+    os.unlink(config_file)
+
+    captured_stderr = capsys.readouterr().err.rstrip()
+    assert sentinal == captured_stderr
+
+    captured_stdout = capsys.readouterr().out.rstrip()
+    assert len(captured_stdout) == 0
+
+
+def test_value_to_stderr_01_upper(capsys):
+    sentinal = "XXXX_foobar01_XXXX"
+    yaml = f"""
+        EXAMPLE:
+            name: null
+            value: "{sentinal}"
+            value_to: "<STDERR>"
+    """
+
+    config_file = __generate_config_file(yaml)
+    EnvAliasGenerator(config_file=config_file).generate()
+    os.unlink(config_file)
+
+    captured_stderr = capsys.readouterr().err.rstrip()
+    assert sentinal == captured_stderr
+
+    captured_stdout = capsys.readouterr().out.rstrip()
+    assert len(captured_stdout) == 0
+
+
+def test_value_to_stderr_02(capsys):
+    sentinal = "XXXX_foobar02_XXXX"
+    yaml = f"""
+        EXAMPLE:
+            name: null
+            value: "{sentinal}"
+            value_to: "<stdout>"
+    """
+
+    config_file = __generate_config_file(yaml)
+    EnvAliasGenerator(config_file=config_file).generate()
+    os.unlink(config_file)
+
+    captured_stdout = capsys.readouterr().out.rstrip()
+    assert sentinal == captured_stdout
+
+    captured_stderr = capsys.readouterr().err.rstrip()
+    assert len(captured_stderr) == 0
+
+
+def __generate_config_file(yaml_config) -> Path:
+    config = "env-alias:" + yaml_config
+    filename = os.path.join(tempfile.gettempdir(), "".join(random.choice(string.ascii_lowercase) for i in range(8)))
+    with open(filename, "w") as f:
+        f.write(config)
+    return Path(filename)