feat: add 'valid_json' function

docs/functions/valid_json.md

@@ -0,0 +1,26 @@
+---
+# generated by https://github.com/hashicorp/terraform-plugin-docs
+page_title: "valid_json function - assert"
+subcategory: ""
+description: |-
+  Checks whether a string is valid JSON
+---
+
+# function: valid_json
+
+
+
+
+
+## Signature
+
+<!-- signature generated by tfplugindocs -->
+```text
+valid_json(json string) bool
+```
+
+## Arguments
+
+<!-- arguments generated by tfplugindocs -->
+1. `json` (String) The JSON string to check
+

internal/provider/provider.go

@@ -65,6 +65,7 @@ func (p *AssertProvider) Functions(ctx context.Context) []func() function.Functi
 		NewNotEqualFunction,
 		NewTrueFunction,
 		NewFalseFunction,
+		NewValidJSONFunction,
 	}
 }
 

internal/provider/valid_json_function.go

@@ -0,0 +1,66 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package provider
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/hashicorp/terraform-plugin-framework/function"
+)
+
+var (
+	_ function.Function = ValidJSONFunction{}
+)
+
+func NewValidJSONFunction() function.Function {
+	return ValidJSONFunction{}
+}
+
+type ValidJSONFunction struct{}
+
+func (r ValidJSONFunction) Metadata(_ context.Context, req function.MetadataRequest, resp *function.MetadataResponse) {
+	resp.Name = "valid_json"
+}
+
+func (r ValidJSONFunction) Definition(_ context.Context, _ function.DefinitionRequest, resp *function.DefinitionResponse) {
+	resp.Definition = function.Definition{
+		Summary: "Checks whether a string is valid JSON",
+		Parameters: []function.Parameter{
+			function.StringParameter{
+				AllowNullValue:     false,
+				AllowUnknownValues: true,
+				Description:        "The JSON string to check",
+				Name:               "json",
+			},
+		},
+		Return: function.BoolReturn{},
+	}
+}
+
+func (r ValidJSONFunction) Run(ctx context.Context, req function.RunRequest, resp *function.RunResponse) {
+	var JSON *string
+
+	resp.Error = function.ConcatFuncErrors(req.Arguments.Get(ctx, &JSON))
+	if resp.Error != nil {
+		return
+	}
+
+	isValidJSON, err := isValidJSON(JSON)
+	if err != nil {
+		resp.Error = function.ConcatFuncErrors(resp.Error, function.NewFuncError(err.Error()))
+		return
+	}
+
+	resp.Error = function.ConcatFuncErrors(resp.Result.Set(ctx, isValidJSON))
+}
+
+func isValidJSON(JSON *string) (bool, error) {
+	var js map[string]interface{}
+	err := json.Unmarshal([]byte(*JSON), &js)
+	if err != nil {
+		return false, nil
+	}
+	return true, nil
+}

internal/provider/valid_json_function_test.go

@@ -0,0 +1,66 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package provider
+
+import (
+	"testing"
+
+	"github.com/hashicorp/go-version"
+	"github.com/hashicorp/terraform-plugin-testing/helper/resource"
+	"github.com/hashicorp/terraform-plugin-testing/tfversion"
+)
+
+func TestValidJSONFunction_basic(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		TerraformVersionChecks: []tfversion.TerraformVersionCheck{
+			tfversion.SkipBelow(version.Must(version.NewVersion("1.8.0-beta1"))),
+		},
+		ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
+		Steps: []resource.TestStep{
+			{
+				Config: `
+				locals {
+				  json = jsonencode({
+				    foo = "bar"
+				  })
+				}
+				output "test" {
+					value = provider::assert::valid_json(local.json)
+				}
+				`,
+				Check: resource.ComposeAggregateTestCheckFunc(
+					resource.TestCheckOutput("test", "true"),
+				),
+			},
+		},
+	})
+}
+
+func TestValidJSONFunction_multiline(t *testing.T) {
+	resource.UnitTest(t, resource.TestCase{
+		TerraformVersionChecks: []tfversion.TerraformVersionCheck{
+			tfversion.SkipBelow(version.Must(version.NewVersion("1.8.0-beta1"))),
+		},
+		ProtoV6ProviderFactories: testAccProtoV6ProviderFactories,
+		Steps: []resource.TestStep{
+			{
+				Config: `
+				locals {
+				  json = <<EOF
+				  {
+					"foo": "bar"
+				  }
+				  EOF
+				}
+				output "test" {
+					value = provider::assert::valid_json(local.json)
+				}
+				`,
+				Check: resource.ComposeAggregateTestCheckFunc(
+					resource.TestCheckOutput("test", "true"),
+				),
+			},
+		},
+	})
+}