[Feature] Added databricks_functions data source (#4154)

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

It's now possible to fetch information about functions defined in a
specific UC schema.

No integration test yet because we don't have `databricks_function`
resource yet.

Resolves #4111

## 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`
- [ ] relevant acceptance tests are passing
- [x] using Go SDK

---------

Co-authored-by: Miles Yucht <[email protected]>

docs/data-sources/functions.md

@@ -0,0 +1,86 @@
+---
+subcategory: "Unity Catalog"
+---
+# databricks_functionss Data Source
+
+-> This data source can only be used with a workspace-level provider!
+
+Retrieves a list of [User-Defined Functions (UDFs) registered in the Unity Catalog](https://docs.databricks.com/en/udf/unity-catalog.html).
+
+## Example Usage
+
+List all functions defined in a specific schema (`main.default` in this example):
+
+```hcl
+data "databricks_functions" "all" {
+  catalog_name = "main"
+  schema_name  = "default"
+}
+
+output "all_external_locations" {
+  value = data.databricks_functions.all.functions
+}
+```
+
+## Argument Reference
+
+The following arguments are supported:
+
+* `catalog_name` - (Required) Name of [databricks_catalog](../resources/catalog.md).
+* `schema_name` - (Required) Name of [databricks_schema](../resources/schema.md).
+* `include_browse` - (Optional, Boolean) flag to specify if include UDFs in the response for which the principal can only access selective metadata for.
+
+## Attribute Reference
+
+This data source exports the following attributes:
+
+* `functions` - list of objects describing individual UDF. Each object consists of the following attributes (refer to [REST API documentation](https://docs.databricks.com/api/workspace/functions/list#functions) for up-to-date list of attributes. Default type is String):
+  * `name` - Name of function, relative to parent schema.
+  * `catalog_name` - Name of parent catalog.
+  * `schema_name` - Name of parent schema relative to its parent catalog.
+  * `input_params` - object describing input parameters. Consists of the single attribute:
+    * `parameters` - The array of definitions of the function's parameters:
+      * `name` - Name of parameter.
+      * `type_text` - Full data type spec, SQL/catalogString text.
+      * `type_json` - Full data type spec, JSON-serialized.
+      * `type_name` - Name of type (INT, STRUCT, MAP, etc.).
+      * `type_precision` - Digits of precision; required on Create for DecimalTypes.
+      * `type_scale` - Digits to right of decimal; Required on Create for DecimalTypes.
+      * `type_interval_type` - Format of IntervalType.
+      * `position` - Ordinal position of column (starting at position 0).
+      * `parameter_mode` - The mode of the function parameter.
+      * `parameter_type` - The type of function parameter (`PARAM` or `COLUMN`).
+      * `parameter_default` - Default value of the parameter.
+      * `comment` - User-provided free-form text description.
+  * `return_params` - Table function return parameters.  See `input_params` for description.
+  * `data_type` - Scalar function return data type.
+  * `full_data_type` - Pretty printed function data type.
+  * `routine_body` - Function language (`SQL` or `EXTERNAL`). When `EXTERNAL` is used, the language of the routine function should be specified in the `external_language` field, and the `return_params` of the function cannot be used (as `TABLE` return type is not supported), and the `sql_data_access` field must be `NO_SQL`.
+  * `routine_definition` - Function body.
+  * `routine_dependencies` - Function dependencies.
+  * `parameter_style` - Function parameter style. `S` is the value for SQL.
+  * `is_deterministic` - Boolean flag specifying whether the function is deterministic.
+  * `sql_data_access` - Function SQL data access (`CONTAINS_SQL`, `READS_SQL_DATA`, `NO_SQL`).
+  * `is_null_call` - Boolean flag whether function null call.
+  * `security_type` - Function security type. (Enum: `DEFINER`).
+  * `specific_name` - Specific name of the function; Reserved for future use.
+  * `external_name` - External function name.
+  * `external_language` - External function language.
+  * `sql_path` - List of schemes whose objects can be referenced without qualification.
+  * `owner` - Username of current owner of function.
+  * `comment` - User-provided free-form text description.
+  * `properties` - JSON-serialized key-value pair map, encoded (escaped) as a string.
+  * `metastore_id` - Unique identifier of parent metastore.
+  * `full_name` - Full name of function, in form of catalog_name.schema_name.function__name
+  * `created_at` - Time at which this function was created, in epoch milliseconds.
+  * `created_by` - Username of function creator.
+  * `updated_at` - Time at which this function was created, in epoch milliseconds.
+  * `updated_by` - Username of user who last modified function.
+  * `function_id` - Id of Function, relative to parent schema.
+  * `browse_only` - Indicates whether the principal is limited to retrieving metadata for the associated object through the `BROWSE` privilege when `include_browse` is enabled in the request.
+
+## Related Resources
+
+The following resources are used in the same context:
+
+* [databricks_schema](./schema.md) to get information about a single schema

internal/providers/pluginfw/pluginfw.go

@@ -16,6 +16,7 @@ import (
 	"github.com/databricks/terraform-provider-databricks/commands"
 	"github.com/databricks/terraform-provider-databricks/common"
 	providercommon "github.com/databricks/terraform-provider-databricks/internal/providers/common"
+	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/catalog"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/cluster"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/library"
 	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/resources/notificationdestinations"
@@ -60,6 +61,7 @@ func (p *DatabricksProviderPluginFramework) DataSources(ctx context.Context) []f
 		notificationdestinations.DataSourceNotificationDestinations,
 		sharing.DataSourceShare,
 		sharing.DataSourceShares,
+		catalog.DataSourceFunctions,
 	}
 }
 

internal/providers/pluginfw/resources/catalog/data_functions.go

@@ -0,0 +1,90 @@
+package catalog
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/databricks/databricks-sdk-go/apierr"
+	"github.com/databricks/databricks-sdk-go/service/catalog"
+	"github.com/databricks/terraform-provider-databricks/common"
+	pluginfwcommon "github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/common"
+	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/converters"
+	"github.com/databricks/terraform-provider-databricks/internal/providers/pluginfw/tfschema"
+	"github.com/databricks/terraform-provider-databricks/internal/service/catalog_tf"
+	"github.com/hashicorp/terraform-plugin-framework/datasource"
+	"github.com/hashicorp/terraform-plugin-framework/datasource/schema"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+)
+
+func DataSourceFunctions() datasource.DataSource {
+	return &FunctionsDataSource{}
+}
+
+var _ datasource.DataSourceWithConfigure = &FunctionsDataSource{}
+
+type FunctionsDataSource struct {
+	Client *common.DatabricksClient
+}
+
+type FunctionsData struct {
+	CatalogName   types.String              `tfsdk:"catalog_name"`
+	SchemaName    types.String              `tfsdk:"schema_name"`
+	IncludeBrowse types.Bool                `tfsdk:"include_browse" tf:"optional"`
+	Functions     []catalog_tf.FunctionInfo `tfsdk:"functions" tf:"optional,computed"`
+}
+
+func (d *FunctionsDataSource) Metadata(ctx context.Context, req datasource.MetadataRequest, resp *datasource.MetadataResponse) {
+	resp.TypeName = "databricks_functions"
+}
+
+func (d *FunctionsDataSource) Schema(ctx context.Context, req datasource.SchemaRequest, resp *datasource.SchemaResponse) {
+	attrs, blocks := tfschema.DataSourceStructToSchemaMap(FunctionsData{}, nil)
+	resp.Schema = schema.Schema{
+		Attributes: attrs,
+		Blocks:     blocks,
+	}
+}
+
+func (d *FunctionsDataSource) Configure(_ context.Context, req datasource.ConfigureRequest, resp *datasource.ConfigureResponse) {
+	if d.Client == nil {
+		d.Client = pluginfwcommon.ConfigureDataSource(req, resp)
+	}
+}
+
+func (d *FunctionsDataSource) Read(ctx context.Context, req datasource.ReadRequest, resp *datasource.ReadResponse) {
+	w, diags := d.Client.GetWorkspaceClient()
+	resp.Diagnostics.Append(diags...)
+	if resp.Diagnostics.HasError() {
+		return
+	}
+
+	var functions FunctionsData
+	diags = req.Config.Get(ctx, &functions)
+	resp.Diagnostics.Append(diags...)
+	if resp.Diagnostics.HasError() {
+		return
+	}
+	catalogName := functions.CatalogName.ValueString()
+	schemaName := functions.SchemaName.ValueString()
+	functionsInfosSdk, err := w.Functions.ListAll(ctx, catalog.ListFunctionsRequest{
+		CatalogName:   catalogName,
+		SchemaName:    schemaName,
+		IncludeBrowse: functions.IncludeBrowse.ValueBool(),
+	})
+	if err != nil {
+		if apierr.IsMissing(err) {
+			resp.State.RemoveResource(ctx)
+		}
+		resp.Diagnostics.AddError(fmt.Sprintf("failed to get functions for %s.%s schema", catalogName, schemaName), err.Error())
+		return
+	}
+	for _, functionSdk := range functionsInfosSdk {
+		var function catalog_tf.FunctionInfo
+		resp.Diagnostics.Append(converters.GoSdkToTfSdkStruct(ctx, functionSdk, &function)...)
+		if resp.Diagnostics.HasError() {
+			return
+		}
+		functions.Functions = append(functions.Functions, function)
+	}
+	resp.Diagnostics.Append(resp.State.Set(ctx, functions)...)
+}