From 66cdc97e9d3b94d158052d306acf6f711f936094 Mon Sep 17 00:00:00 2001
From: Ansgar Mertens <ansgar@hashicorp.com>
Date: Fri, 17 Jan 2025 16:39:36 +0100
Subject: [PATCH] feat: Collect write only attributes via PathDecoder (#442)

---
 decoder/write_only_attributes.go | 76 ++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 decoder/write_only_attributes.go

diff --git a/decoder/write_only_attributes.go b/decoder/write_only_attributes.go
new file mode 100644
index 00000000..672c0ae9
--- /dev/null
+++ b/decoder/write_only_attributes.go
@@ -0,0 +1,76 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+package decoder
+
+import (
+	"github.com/hashicorp/hcl-lang/decoder/internal/ast"
+	"github.com/hashicorp/hcl-lang/decoder/internal/schemahelper"
+	"github.com/hashicorp/hcl-lang/schema"
+	"github.com/hashicorp/hcl/v2"
+)
+
+type WriteOnlyAttribute struct {
+	Name     string
+	Resource string
+}
+
+type WriteOnlyAttributes []WriteOnlyAttribute
+
+func (d *PathDecoder) CollectWriteOnlyAttributes() (WriteOnlyAttributes, error) {
+	if d.pathCtx.Schema == nil {
+		// unable to collect write-only attributes without schema
+		return nil, &NoSchemaError{}
+	}
+
+	attrs := make(WriteOnlyAttributes, 0)
+	files := d.filenames()
+	for _, filename := range files {
+		f, err := d.fileByName(filename)
+		if err != nil {
+			// skip unparseable file
+			continue
+		}
+		attrs = append(attrs, d.decodeWriteOnlyAttributesForBody(f.Body, d.pathCtx.Schema)...)
+	}
+
+	return attrs, nil
+}
+
+func (d *PathDecoder) decodeWriteOnlyAttributesForBody(body hcl.Body, bodySchema *schema.BodySchema) WriteOnlyAttributes {
+	woAttrs := make(WriteOnlyAttributes, 0)
+
+	if bodySchema == nil {
+		return WriteOnlyAttributes{}
+	}
+
+	content := ast.DecodeBody(body, bodySchema)
+
+	for _, block := range content.Blocks {
+		if block.Type == "resource" {
+			blockSchema, ok := bodySchema.Blocks[block.Type]
+			if !ok {
+				// unknown block (no schema)
+				continue
+			}
+
+			mergedSchema, _ := schemahelper.MergeBlockBodySchemas(block.Block, blockSchema)
+
+			blockContent := ast.DecodeBody(block.Body, blockSchema.Body)
+
+			for _, attr := range blockContent.Attributes {
+				attrSchema, ok := mergedSchema.Attributes[attr.Name]
+				if ok && attrSchema.IsWriteOnly {
+
+					woAttrs = append(woAttrs, WriteOnlyAttribute{
+						Name:     attr.Name,
+						Resource: block.Labels[0],
+					})
+
+				}
+			}
+		}
+	}
+
+	return woAttrs
+}