[Exporter] Initial support for resources implemented with plugin framework (#5176)

## Changes
<!-- Summary of your changes that are easy to understand -->

This PR adds support for Terraform Plugin Framework-based resources to
the exporter, which previously only supported legacy SDKv2 resources.
The implementation uses a hybrid approach that maximizes code reuse
(~70%) while respecting the framework-specific HCL syntax differences.

Resolves: #4050

### Key Changes

**Abstraction Layer**: Introduced `ResourceDataWrapper`,
`SchemaWrapper`, and `FieldSchema` interfaces in
`exporter/abstractions.go` to provide a unified way to interact with
both SDKv2's `schema.ResourceData` and Plugin Framework's `tfsdk.State`.
These abstractions enable the exporter to read resource data, access
schemas, and query field types consistently across both frameworks.

**Unified Code Generation**: Implemented a hybrid HCL generation
approach in `exporter/codegen.go` with a single entry point
`unifiedDataToHcl()`. The implementation extracts ~70% of common logic
into shared helper functions (`extractFieldsForGeneration()`,
`generateDependsOnAttribute()`), while maintaining framework-specific
functions (`generateSdkv2Field()`, `generatePluginFrameworkField()`) for
handling the key difference: SDKv2 generates nested structures as blocks
(`evaluation { ... }`), while Plugin Framework uses attribute syntax
(`evaluation = { ... }`).

**New Unified Callbacks**: Added `ShouldOmitFieldUnified` and
`ShouldGenerateFieldUnified` to the `importable` struct, which work with
both frameworks through the abstraction layers. Legacy callbacks
(`ShouldOmitField`, `ShouldGenerateField`) remain for backward
compatibility, and resources can be gradually migrated to the unified
versions. The default omission logic was also corrected to properly skip
all computed fields, matching the original SDKv2 behavior.

**Plugin Framework Resource Support**: Implemented full support for
`databricks_alert_v2` as the first Plugin Framework resource. The
implementation includes proper state initialization, conversion helpers
(`convertPluginFrameworkToGoSdk`), dependency emission, and correct
handling of nested attributes. Added comprehensive test fixtures
(`emptyAlertsV2`) to ensure compatibility with existing test suites.

### Testing & Documentation

All existing tests pass, including critical code generation tests
(`TestNotebookGeneration`, `TestDirectoryGeneration`,
`TestImportingSqlObjects`). Updated `AGENTS.md` with the new unified
code generation architecture and added the exporter architecture
section. Updated `docs/guides/experimental-exporter.md` support matrix
to reflect support for both `databricks_alert` and `databricks_alert_v2`
resources.

### Benefits

This implementation maintains 100% backward compatibility with existing
SDKv2 resources while enabling easy addition of new Plugin Framework
resources. The unified approach reduces technical debt, provides a
single source of truth for business logic, and makes future maintenance
significantly easier as the provider transitions to Plugin Framework.

## Tests
<!--
How is this tested? Please see the checklist below and also describe any
other relevant tests
-->

- [x] `make test` run locally
- [x] relevant change in `docs/` folder
- [ ] covered with integration tests in `internal/acceptance`
- [ ] using Go SDK
- [x] using TF Plugin Framework
- [x] has entry in `NEXT_CHANGELOG.md` file

Author: alexott

AGENTS.md

@@ -95,6 +95,45 @@ Resources are being migrated from SDKv2 to Plugin Framework. When migrating:
   - `TestMwsAcc*` - Account-level tests across all clouds
   - `TestUcAcc*` - Unity Catalog tests across all clouds
 
+### Exporter Architecture
+
+The exporter (`exporter/` directory) generates Terraform configuration (`.tf` files) and import scripts from existing Databricks resources.
+
+#### Unified HCL Code Generation
+
+The exporter uses a **unified code generation approach** for both SDKv2 and Plugin Framework resources:
+
+**Entry Point**: `unifiedDataToHcl()` in `exporter/codegen.go`
+- Works with both SDKv2 and Plugin Framework resources through abstraction layers
+- Uses `ResourceDataWrapper` and `SchemaWrapper` interfaces for unified data access
+- Extracts ~70% of common logic into shared helper functions
+
+**Architecture**:
+```
+unifiedDataToHcl()
+├── extractFieldsForGeneration() ← Shared: field iteration, omission, variable refs, skip logic
+├── generateSdkv2Field() ← SDKv2-specific: generates blocks
+├── generatePluginFrameworkField() ← Plugin Framework-specific: generates attributes
+└── generateDependsOnAttribute() ← Shared: depends_on generation
+```
+
+**Resource Definition Callbacks** (`importable` struct in `exporter/model.go`):
+- `ShouldOmitFieldUnified` - Unified callback for field omission (works with both frameworks)
+- `ShouldGenerateFieldUnified` - Unified callback for field generation (works with both frameworks)
+- `ShouldOmitField` - Legacy SDKv2-only callback (deprecated, use Unified version)
+- `ShouldGenerateField` - Legacy SDKv2-only callback (deprecated, use Unified version)
+
+**Key Differences**:
+- SDKv2 generates nested structures as **blocks**: `evaluation { ... }`
+- Plugin Framework generates nested structures as **attributes**: `evaluation = { ... }`
+
+**When Adding Exporter Support**:
+1. Define resource in `exporter/importables.go` with `PluginFramework: true` for Plugin Framework resources
+2. Implement `List` function to discover resources
+3. Implement `Import` function to emit dependencies (use `convertPluginFrameworkToGoSdk` helper for Plugin Framework)
+4. Define `Depends` relationships for cross-resource references
+5. Use unified callbacks (`ShouldOmitFieldUnified`, `ShouldGenerateFieldUnified`) for custom field logic
+
 ### Dual-Provider Resource Patterns
 
 #### Import Handling for Account/Workspace Resources

NEXT_CHANGELOG.md

@@ -14,4 +14,6 @@
 
 ### Exporter
 
+* Initial support for resources implemented with plugin framework ([#5176](https://github.com/databricks/terraform-provider-databricks/pull/5176)).
+
 ### Internal Changes

docs/guides/experimental-exporter.md

@@ -154,7 +154,7 @@ Services could be specified in combination with predefined aliases (`all` - for
 -> Please note that for services not marked with **listing**, we'll export resources only if they are referenced from other resources.
 
 * `access` -  **listing** [databricks_permissions](../resources/permissions.md), [databricks_instance_profile](../resources/instance_profile.md), [databricks_ip_access_list](../resources/ip_access_list.md), and [databricks_access_control_rule_set](../resources/access_control_rule_set.md).   *Please note that for `databricks_permissions` we list only `authorization = "tokens"`, the permissions for other objects (notebooks, ...) will be emitted when corresponding objects are processed!*
-* `alerts` - **listing** [databricks_alert](../resources/alert.md).
+* `alerts` - **listing** [databricks_alert](../resources/alert.md) and [databricks_alert_v2](../resources/alert_v2.md).
 * `billing` - **listing** [databricks_budget](../resources/budget.md).
 * `compute` - **listing** [databricks_cluster](../resources/cluster.md).
 * `dashboards` - **listing** [databricks_dashboard](../resources/dashboard.md).
@@ -219,6 +219,8 @@ Exporter aims to generate HCL code for most of the resources within the Databric
 | Resource | Supported | Incremental | Workspace | Account |
 | --- | --- | --- | --- | --- |
 | [databricks_access_control_rule_set](../resources/access_control_rule_set.md) | Yes | No | No | Yes |
+| [databricks_alert](../resources/alert.md) | Yes | Yes | Yes | No |
+| [databricks_alert_v2](../resources/alert_v2.md) | Yes | Yes | Yes | No |
 | [databricks_artifact_allowlist](../resources/artifact_allowlist.md) | Yes | No | Yes | No |
 | [databricks_budget](../resources/budget.md) | Yes | Yes | No | Yes |
 | [databricks_catalog](../resources/catalog.md) | Yes | Yes | Yes | No |
@@ -264,6 +266,7 @@ Exporter aims to generate HCL code for most of the resources within the Databric
 | [databricks_online_table](../resources/online_table.md) | Yes | Yes | Yes | No |
 | [databricks_permissions](../resources/permissions.md) | Yes | No | Yes | No |
 | [databricks_pipeline](../resources/pipeline.md) | Yes | Yes | Yes | No |
+| [databricks_query](../resources/query.md) | Yes | Yes | Yes | No |
 | [databricks_recipient](../resources/recipient.md) | Yes | Yes | Yes | No |
 | [databricks_registered_model](../resources/registered.md) | Yes | Yes | Yes | No |
 | [databricks_repo](../resources/repo.md) | Yes | No | Yes | No |