feat(gazelle): enable pyi attrs by default (bazel-contrib#3753)

Default python_generate_pyi_deps and python_generate_pyi_srcs to true so
generated targets preserve type-only dependencies and sibling stub files
without extra directives. These directives have been available for many
versions now, and defaulting to true better matches the intended
semantics of current rules_python versions.

Write detailed docs for `python_generate_pyi_deps` since that was
missing.

Author: amartani

CHANGELOG.md

@@ -60,6 +60,8 @@ END_UNRELEASED_TEMPLATE
 ### Changed
 * (gazelle) WORKSPACE's bazel-gazelle dependency bumped from 0.36.0 to 0.47.0.
   The go version was also bumped from 1.21.13 to 1.22.9.
+* (gazelle) `python_generate_pyi_deps` and `python_generate_pyi_srcs` now
+  default to `true`.
 * (pypi) The data files of a wheel (bin, includes, etc) are now always included
   as a library's data dependencies.
 

gazelle/docs/directives.md

@@ -147,18 +147,18 @@ The Python-specific directives are:
 [`# gazelle:python_generate_pyi_deps bool`](#directive-python-generate-pyi-deps)
 : Controls whether to generate a separate `pyi_deps` attribute for
   type-checking dependencies or merge them into the regular `deps`
-  attribute. When `false` (default), type-checking dependencies are
-  merged into `deps` for backward compatibility. When `true`, generates
-  separate `pyi_deps`. Imports in blocks with the format
+  attribute. When `true` (default), generates separate `pyi_deps`. When
+  `false`, type-checking dependencies are merged into `deps`. Imports in
+  blocks with the format
   `if typing.TYPE_CHECKING:` or `if TYPE_CHECKING:` and type-only stub
   packages (eg. boto3-stubs) are recognized as type-checking dependencies.
-  * Default: `false`
+  * Default: `true`
   * Allowed Values: `true`, `false`
 
 [`# gazelle:python_generate_pyi_srcs bool`](#directive-python-generate-pyi-srcs)
 : Controls whether to generate a `pyi_srcs` attribute if a sibling `.pyi` file
-  is found. When `false` (default), the `pyi_srcs` attribute is not added.
-  * Default: `false`
+  is found. When `false`, the `pyi_srcs` attribute is not added.
+  * Default: `true`
   * Allowed Values: `true`, `false`
 
 [`# gazelle:python_generate_proto bool`](#directive-python-generate-proto)
@@ -681,10 +681,42 @@ that are relative to the current package.
 {gh-pr}`3014`
 :::
 
-:::{error}
-Detailed docs are not yet written.
+:::{versionchanged} VERSION_NEXT_FEATURE
+The default was changed from `false` to `true`. {gh-pr}`3753`
 :::
 
+When `true`, Gazelle writes type-checking dependencies to the `pyi_deps`
+attribute instead of merging them into `deps`. This is the default behavior.
+
+Gazelle treats imports inside `if TYPE_CHECKING:` and
+`if typing.TYPE_CHECKING:` blocks as type-checking dependencies. It also adds
+type stub packages, such as `boto3-stubs`, to `pyi_deps` when the corresponding
+runtime package is imported normally.
+
+For example, assume you have the following file:
+
+```python
+import boto3
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    import requests
+```
+
+The generated target will be:
+
+```starlark
+py_library(
+    name = "foo",
+    srcs = ["foo.py"],
+    pyi_deps = ["@pip//requests"],
+    deps = ["@pip//boto3"],
+)
+```
+
+When `false`, Gazelle merges type-checking dependencies into `deps` and does
+not write `pyi_deps`.
+
 
 (directive-python-generate-pyi-srcs)=
 ## `python_generate_pyi_srcs`
@@ -693,6 +725,10 @@ Detailed docs are not yet written.
 {gh-pr}`3356`
 :::
 
+:::{versionchanged} VERSION_NEXT_FEATURE
+The default was changed from `false` to `true`. {gh-pr}`3753`
+:::
+
 When `true`, include any sibling `.pyi` files in the `pyi_srcs` target attribute.
 
 For example, assume you have the following files:

gazelle/pythonconfig/pythonconfig.go

@@ -102,11 +102,11 @@ const (
 	ExperimentalAllowRelativeImports = "python_experimental_allow_relative_imports"
 	// GeneratePyiDeps represents the directive that controls whether to generate
 	// separate pyi_deps attribute or merge type-checking dependencies into deps.
-	// Defaults to false for backward compatibility.
+	// Defaults to true.
 	GeneratePyiDeps = "python_generate_pyi_deps"
 	// GeneratePyiSrcs represents the directive that controls whether to include
 	// a pyi_srcs attribute if a sibling .pyi file is found.
-	// Defaults to false for backward compatibility.
+	// Defaults to true.
 	GeneratePyiSrcs = "python_generate_pyi_srcs"
 	// GenerateProto represents the directive that controls whether to generate
 	// python_generate_proto targets.
@@ -256,8 +256,8 @@ func New(
 		labelConvention:                           DefaultLabelConvention,
 		labelNormalization:                        DefaultLabelNormalizationType,
 		experimentalAllowRelativeImports:          false,
-		generatePyiDeps:                           false,
-		generatePyiSrcs:                           false,
+		generatePyiDeps:                           true,
+		generatePyiSrcs:                           true,
 		generateProto:                             false,
 		resolveSiblingImports:                     false,
 		includeAncestorConftest:                   true,