Merge pull request #981 from guardrails-ai/hub-contribution-doc

Validator Concept Doc

docs/concepts/validators.md

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+# Validators
+
+Validators are how we apply quality controls to the outputs of LLMs.  They specify the criteria to measure whether an output is valid, as well as what actions to take when an output does not meet those criteria.
+
+## How do Validators work?
+Each validator is a method that encodes some criteria, and checks if a given value meets that criteria.
+
+- If the value passes the criteria defined, the validator returns `PassResult`. In most cases this means returning that value unchanged. In very few advanced cases, there may be a a value override (the specific validator will document this).
+- If the value does not pass the criteria, a `FailResult` is returned.  In this case, the validator applies the user-configured `on_fail` policies (see [On-Fail Policies](/docs/hub/concepts/on_fail_policies.md) for more details).
+
+## Runtime Metadata
+
+Occasionally, validators need additional metadata that is only available during runtime. Metadata could be data generated during the execution of a validator (*important if you're writing your own validators*), or could just be a container for runtime arguments.
+
+As an example, the `ExtractedSummarySentencesMatch` validator accepts a `filepaths` property in the metadata dictionary to specify what source files to compare the summary against to ensure similarity.  Unlike arguments which are specified at validator initialization, metadata is specified when calling `guard.validate` or `guard.__call__` (this is the `guard()` function). For more information on how to use metadata, see [How to use Metadata](/docs/hub/how_to_guides/metadata.md).
+
+```python
+guard = Guard.from_rail("my_railspec.rail")
+
+outcome = guard(
+    llm_api=openai.chat.completions.create,
+    model="gpt-3.5-turbo",
+    num_reasks=3,
+    metadata={
+        "filepaths": [
+            "./my_data/article1.txt",
+            "./my_data/article2.txt",
+        ]
+    }
+)
+```
+
+## Custom Validators
+
+If you need to perform a validation that is not currently supported by the hub, you can create your own custom validators.
+
+A custom validator can be as simple as a single function if you do not require addtional arguments:
+
+```py
+from typing import Dict
+from guardrails.validators import (
+    FailResult,
+    PassResult,
+    register_validator,
+    ValidationResult,
+)
+
+@register_validator(name="starts-with-a", data_type="string")
+def starts_with_a(value: str, metadata: Dict) -> ValidationResult:
+    if value.startswith("a"):
+        return PassResult()
+
+    return FailResult(
+        error_message=f"Value {value} does not start with a.",
+        fix_value="a" + value,
+    )
+```
+
+:::note
+A fix_value was supplied in the FailResult in the example above. This value represents a programmatic fix that can be applied to the output if `on_fail='fix'` is passed during validator initialization.
+:::
+
+If you need to perform more complex operations or require addtional arguments to perform the validation, then the validator can be specified as a class that inherits from our base Validator class:
+
+```py
+from typing import Callable, Dict, Optional
+from guardrails.validators import (
+    FailResult,
+    PassResult,
+    register_validator,
+    ValidationResult,
+    Validator,
+)
+
+@register_validator(name="starts-with", data_type="string")
+class StartsWith(Validator):
+    def __init__(self, prefix: str, on_fail: Optional[Callable] = None):
+        super().__init__(on_fail=on_fail, prefix=prefix)
+        self.prefix = prefix
+
+    def validate(self, value: str, metadata: Dict) -> ValidationResult:
+        if value.startswith(self.prefix):
+            return PassResult()
+
+        return FailResult(
+            error_message=f"Value {value} does not start with {self.prefix}.",
+            fix_value=self.prefix + value,  # To enable the "fix" option for on-fail
+        )
+```
+
+Custom validators must be defined before creating a `Guard` or `RAIL` spec in the code, 
+but otherwise can be used like built in validators. It can be used in a `RAIL` spec OR
+a `Pydantic` model like so:
+
+Custom validators must be defined before creating a `Guard` in the code, 
+but otherwise can be used just like built in validators.
+
+### Guard.use Example
+```py
+from guardrails import Guard
+from .my_custom_validators import starts_with_a, StartsWith
+
+guard = Guard().use(
+    StartsWith("my-prefix")
+).use(
+    starts_with_a()
+)
+```
+
+### Pydantic Example
+```py
+from guardrails import Guard
+from pydantic import BaseModel, Field
+from .my_custom_validators import starts_with_a, StartsWith
+
+class MyModel(BaseModel):
+    a_string: Field(validators=[starts_with_a()])
+    custom_string: Field(validators=[StartsWith("my-prefix")])
+
+guard = Guard.from_pydantic(MyModel)
+```
+
+### RAIL Example
+```xml
+<rail version="0.1">
+...
+<output>
+    <string name="a_string" type="string" validators="starts-with-a">
+    <string name="custom_string" type="string" validators="starts-with: my-prefix">
+</output>
+...
+</rail>
+``` 
+
+## Submitting a Custom Validator to the Hub
+
+There are two ways to create a new validator and submit it to the Hub.
+
+1. For lightweight validators, use the `hub` CLI to create a new validator and submit it to the Hub.
+2. For more complex validators, clone the Validator-Template repository and register the validator via the Guardrails Hub website.
+
+### Creating a new validator using the `hub` CLI
+
+The `hub` CLI provides a simple way to create a new validator and submit it to the Hub. The `hub` CLI will create a new validator in the current directory and submit it to the Hub.
+
+To create a new validator using the `hub` CLI, run the following command:
+
+```bash
+guardrails hub create-validator my_validator
+```
+
+This will create a new file called `my_validator.py` in the current directory. The file will contain a template and instructions for creating a new validator.
+
+```bash
+guardrails hub submit my_validator
+```
+
+### Creating a new validator using the Validator-Template repository
+
+For more complex validators, you can clone the [Validator-Template repository](https://github.com/guardrails-ai/validator-template) and register the validator via a Google Form on the Guardrails Hub website.
+
+```bash
+git clone git@github.com:guardrails-ai/validator-template.git
+```
+
+Once the repository is cloned and the validator is created, you can register the validator via this [Google Form](https://forms.gle/N6UaE9611niuMxZj7).
+
+
+