docs: adds UPGRADING.md, not to readme, to help inform users about mi…

…gration to v2 (#245)

* docs: adds UPGRADING.md, not to readme, to help inform users about migration to v2

* docs: erroneous version number

* Update UPGRADING.md

Co-authored-by: BenWhitehead <BenWhitehead@users.noreply.github.com>

* docs: clarify enums statement

Co-authored-by: BenWhitehead <BenWhitehead@users.noreply.github.com>

release-as: 2.0.0

README.rst

@@ -62,7 +62,7 @@ Deprecated Python Versions
 Python == 2.7.
 
 The last version of this library compatible with Python 2.7 is
-google-cloud-firestore==1.8.1.
+google-cloud-firestore==1.9.0.
 
 Mac/Linux
 ^^^^^^^^^

UPGRADING.md

@@ -0,0 +1,134 @@
+# 2.0.0 Migration Guide
+
+The 2.0 release of the `google-cloud-firestore` client is a significant upgrade based on a [next-gen code generator](https://github.com/googleapis/gapic-generator-python), and includes substantial interface changes. Existing code written for earlier versions of this library may require updates to use this version. This document describes the changes that have been made, and what you need to do to update your usage.
+
+If you experience issues or have questions, please file an [issue](https://github.com/googleapis/python-firestore/issues).
+
+## Supported Python Versions
+
+> **WARNING**: Breaking change
+
+The 2.0.0 release requires Python 3.6+.
+
+
+## Method Calls
+
+> **WARNING**: Breaking change
+
+If you previously were using modules or functions under the namespace
+`google.cloud.firestore_v1.gapic` there is a high likelihood you have incompatible code.
+To assist with this, we have included some helpful scripts to make some of the code
+modifications required to use 2.0.0.
+
+* Install the library
+
+```py
+python3 -m pip install google-cloud-firestore
+```
+
+* The scripts `fixup_firestore_v1_keywords.py` and `fixup_firestore_admin_v1_keywords.py` 
+is shipped with the library. It expects an input directory (with the code to convert)
+and an empty destination directory.
+
+```sh
+$ fixup_firestore_v1_keywords.py --input-directory .samples/ --output-directory samples/
+$ fixup_firestore_admin_v1_keywords.py --input-directory .samples/ --output-directory samples/
+```
+
+### More Details
+
+In `google-cloud-firestore<2.0.0`, parameters required by the API were positional parameters and optional parameters were keyword parameters.
+
+**Before:**
+```py
+    def a_method(
+        self,
+        param1,
+        param2,
+        param3,
+        retry=google.api_core.gapic_v1.method.DEFAULT,
+        timeout=google.api_core.gapic_v1.method.DEFAULT,
+        metadata=None,
+    ):
+```
+
+In the 2.0.0 release, all methods have a single positional parameter `request`. Method docstrings indicate whether a parameter is required or optional.
+
+Some methods have additional keyword only parameters. The available parameters depend on the `google.api.method_signature` annotation specified by the API producer.
+
+
+**After:**
+```py
+    def a_method(
+        self,
+        request: RequestType = None,
+        *
+        param1,
+        param2,
+        param3,
+        retry=google.api_core.gapic_v1.method.DEFAULT,
+        timeout=google.api_core.gapic_v1.method.DEFAULT,
+        metadata=None,
+    ):
+```
+
+> **NOTE:** The `request` parameter and flattened keyword parameters for the API are mutually exclusive.
+> Passing both will result in an error.
+
+
+Both of these calls are valid:
+
+```py
+response = client.a_method(
+    request={
+        "param1": param1,
+        "param2": param2,
+        "param3": param3
+    }
+)
+```
+
+```py
+response = client.a_method(
+    param1=param1,
+    param2=param2,
+    param3=param3
+)
+```
+
+This call is invalid because it mixes `request` with a keyword argument `param1`. Executing this code
+will result in an error.
+
+```py
+response = client.a_method(
+    request={
+        "param1": param1,
+        "param2": param2
+    },
+    param2=param2
+)
+```
+
+
+
+## Enums and Types
+
+
+> **WARNING**: Breaking change
+
+The `enums` submodule has been removed.
+
+**Before:**
+```py
+from google.cloud import firestore_v1
+
+direction = firestore_v1.enums.StructuredQuery.Direction.ASCENDING
+```
+
+
+**After:**
+```py
+from google.cloud import firestore_v1
+
+direction = firestore_v1.types.StructuredQuery.Direction.ASCENDING
+```

docs/UPGRADING.md

@@ -0,0 +1,134 @@
+# 2.0.0 Migration Guide
+
+The 2.0 release of the `google-cloud-firestore` client is a significant upgrade based on a [next-gen code generator](https://github.com/googleapis/gapic-generator-python), and includes substantial interface changes. Existing code written for earlier versions of this library may require updates to use this version. This document describes the changes that have been made, and what you need to do to update your usage.
+
+If you experience issues or have questions, please file an [issue](https://github.com/googleapis/python-firestore/issues).
+
+## Supported Python Versions
+
+> **WARNING**: Breaking change
+
+The 2.0.0 release requires Python 3.6+.
+
+
+## Method Calls
+
+> **WARNING**: Breaking change
+
+If you previously were using modules or functions under the namespace
+`google.cloud.firestore_v1.gapic` there is a high likelihood you have incompatible code.
+To assist with this, we have includes some helpful scripts to make some of the code
+modifications required to use 2.0.0.
+
+* Install the library
+
+```py
+python3 -m pip install google-cloud-firestore
+```
+
+* The scripts `fixup_firestore_v1_keywords.py` and `fixup_firestore_admin_v1_keywords.py` 
+is shipped with the library. It expects an input directory (with the code to convert)
+and an empty destination directory.
+
+```sh
+$ fixup_firestore_v1_keywords.py --input-directory .samples/ --output-directory samples/
+$ fixup_firestore_admin_v1_keywords.py --input-directory .samples/ --output-directory samples/
+```
+
+### More Details
+
+In `google-cloud-firestore<2.0.0`, parameters required by the API were positional parameters and optional parameters were keyword parameters.
+
+**Before:**
+```py
+    def a_method(
+        self,
+        param1,
+        param2,
+        param3,
+        retry=google.api_core.gapic_v1.method.DEFAULT,
+        timeout=google.api_core.gapic_v1.method.DEFAULT,
+        metadata=None,
+    ):
+```
+
+In the 2.0.0 release, all methods have a single positional parameter `request`. Method docstrings indicate whether a parameter is required or optional.
+
+Some methods have additional keyword only parameters. The available parameters depend on the `google.api.method_signature` annotation specified by the API producer.
+
+
+**After:**
+```py
+    def a_method(
+        self,
+        request: RequestType = None,
+        *
+        param1,
+        param2,
+        param3,
+        retry=google.api_core.gapic_v1.method.DEFAULT,
+        timeout=google.api_core.gapic_v1.method.DEFAULT,
+        metadata=None,
+    ):
+```
+
+> **NOTE:** The `request` parameter and flattened keyword parameters for the API are mutually exclusive.
+> Passing both will result in an error.
+
+
+Both of these calls are valid:
+
+```py
+response = client.a_method(
+    request={
+        "param1": param1,
+        "param2": param2,
+        "param3": param3
+    }
+)
+```
+
+```py
+response = client.a_method(
+    param1=param1,
+    param2=param2,
+    param3=param3
+)
+```
+
+This call is invalid because it mixes `request` with a keyword argument `param1`. Executing this code
+will result in an error.
+
+```py
+response = client.a_method(
+    request={
+        "param1": param1,
+        "param2": param2
+    },
+    param2=param2
+)
+```
+
+
+
+## Enums and Types
+
+
+> **WARNING**: Breaking change
+
+The submodules `enums` and `types` have been removed.
+
+**Before:**
+```py
+from google.cloud import firestore_v1
+
+direction = firestore_v1.enums.StructuredQuery.Direction.ASCENDING
+```
+
+
+**After:**
+```py
+from google.cloud import firestore_v1
+
+direction = firestore_v1.types.StructuredQuery.Direction.ASCENDING
+```