From b6739829e75577fefe2485e062cd08cd9453bbe4 Mon Sep 17 00:00:00 2001
From: Alisdair McDiarmid <alisdair@users.noreply.github.com>
Date: Wed, 24 Jun 2020 15:54:46 -0400
Subject: [PATCH] command: Fix 0.13upgrade to preserve more comments

Previously, any comments inside the required provider configuration for
a given provider would be wiped out upon rerunning the 0.13upgrade
command. This commit attempts to preserve those comments if the existing
entry is semantically equivalent to the entry we are about to write.
---
 command/013_config_upgrade.go                       | 13 ++++++++++++-
 .../013upgrade-preserves-comments/expected/main.tf  |  9 ++++++++-
 .../013upgrade-preserves-comments/input/main.tf     | 10 ++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/command/013_config_upgrade.go b/command/013_config_upgrade.go
index 81494e8f5..06ef7d2d6 100644
--- a/command/013_config_upgrade.go
+++ b/command/013_config_upgrade.go
@@ -404,7 +404,18 @@ command and dealing with them before running this command again.
 			} else {
 				attributesObject = cty.EmptyObjectVal
 			}
-			body.SetAttributeValue(localName, attributesObject)
+			// If this block already has an entry for this local name, we only
+			// want to replace it if it's semantically different
+			if existing := body.GetAttribute(localName); existing != nil {
+				bytes := existing.Expr().BuildTokens(nil).Bytes()
+				expr, _ := hclsyntax.ParseExpression(bytes, "", hcl.InitialPos)
+				value, _ := expr.Value(nil)
+				if !attributesObject.RawEquals(value) {
+					body.SetAttributeValue(localName, attributesObject)
+				}
+			} else {
+				body.SetAttributeValue(localName, attributesObject)
+			}
 
 			// If we don't have a source attribute, manually construct a commented
 			// block explaining what to do
diff --git a/command/testdata/013upgrade-preserves-comments/expected/main.tf b/command/testdata/013upgrade-preserves-comments/expected/main.tf
index 13bbe0b95..7ddfeb0ff 100644
--- a/command/testdata/013upgrade-preserves-comments/expected/main.tf
+++ b/command/testdata/013upgrade-preserves-comments/expected/main.tf
@@ -9,8 +9,15 @@ terraform {
       source  = "hashicorp/bar"
       version = "0.5.0"
     }
+    # An explicit requirement
+    baz = {
+      # Comment inside the block should stay
+      source = "foo/baz"
+    }
+    # Foo is required
     foo = {
-      source = "hashicorp/foo"
+      source  = "hashicorp/foo"
+      version = "1.0.0"
     }
   }
 }
diff --git a/command/testdata/013upgrade-preserves-comments/input/main.tf b/command/testdata/013upgrade-preserves-comments/input/main.tf
index c384d2819..7d12b4337 100644
--- a/command/testdata/013upgrade-preserves-comments/input/main.tf
+++ b/command/testdata/013upgrade-preserves-comments/input/main.tf
@@ -6,5 +6,15 @@ terraform {
   required_providers {
     # Pin bar to this version
     bar = "0.5.0"
+    # An explicit requirement
+    baz = {
+      # Comment inside the block should stay
+      source = "foo/baz"
+    }
+    # Foo is required
+    foo = {
+      # This comment sadly won't make it
+      version = "1.0.0"
+    }
   }
 }