Preserve User-Defined Variable File Order (#13350)

* modifying the for loop to preserver user inputted variable files preference

* adding test cases

* pr comments + refactoring the for loop for better readability.

* pr comments + refactoring the for loop for better readability.

* pr comments | handling default case

* adding additional test case

* fixing test cases

* fixing test cases. creating a subdirectory to add a test case for both hcl and json auto var files

* adding test case for json auto var file

command/build_test.go

@@ -106,6 +106,21 @@ func TestBuild(t *testing.T) {
 			},
 			fileCheck: fileCheck{expected: []string{"chocolate.txt"}},
 		},
+		{
+			name: "var-args: json - auto varfile sets a peanut env var",
+			args: []string{
+				testFixture("var-arg", "var-arg-test-autovar-json"),
+			},
+			fileCheck: fileCheck{expected: []string{"peanut.txt"}},
+		},
+
+		{
+			name: "var-args: hcl - auto varfile and json -auto varfile sets the value in json auto varfile",
+			args: []string{
+				testFixture("var-arg", "var-arg-tests"),
+			},
+			fileCheck: fileCheck{expected: []string{"peanut.txt"}},
+		},
 
 		{
 			name: "var-args: hcl - hcl varfile sets a apple env var",
@@ -124,6 +139,24 @@ func TestBuild(t *testing.T) {
 			},
 			fileCheck: fileCheck{expected: []string{"apple.txt"}},
 		},
+		{
+			name: "var-args: banana json var file then hcl var file sets apple env var",
+			args: []string{
+				"-var-file=" + filepath.Join(testFixture("var-arg"), "banana.json"),
+				"-var-file=" + filepath.Join(testFixture("var-arg"), "apple.hcl"),
+				testFixture("var-arg"),
+			},
+			fileCheck: fileCheck{expected: []string{"apple.txt"}},
+		},
+		{
+			name: "var-args:  apple hcl var file then banana json var file sets banana env var",
+			args: []string{
+				"-var-file=" + filepath.Join(testFixture("var-arg"), "apple.hcl"),
+				"-var-file=" + filepath.Join(testFixture("var-arg"), "banana.json"),
+				testFixture("var-arg"),
+			},
+			fileCheck: fileCheck{expected: []string{"banana.txt"}},
+		},
 
 		{
 			name: "var-args: hcl - arg sets a tomato env var",

command/test-fixtures/var-arg/banana.json

@@ -0,0 +1,3 @@
+{
+  "fruit": "banana"
+}

command/test-fixtures/var-arg/var-arg-test-autovar-json/fruit_builder.pkr.hcl

@@ -0,0 +1,22 @@
+
+variable "fruit" {
+  type = string
+}
+
+locals {
+  fruit = var.fruit
+}
+
+source "null" "builder" {
+  communicator = "none"
+}
+
+build {
+  sources = [
+    "source.null.builder",
+  ]
+
+  provisioner "shell-local" {
+    inline = ["echo ${local.fruit} > ${local.fruit}.txt"]
+  }
+}

command/test-fixtures/var-arg/var-arg-test-autovar-json/peanut.auto.pkrvars.json

@@ -0,0 +1,3 @@
+{
+  "fruit": "peanut" 
+}

command/test-fixtures/var-arg/var-arg-tests/fruit_builder.pkr.hcl

@@ -0,0 +1,22 @@
+
+variable "fruit" {
+  type = string
+}
+
+locals {
+  fruit = var.fruit
+}
+
+source "null" "builder" {
+  communicator = "none"
+}
+
+build {
+  sources = [
+    "source.null.builder",
+  ]
+
+  provisioner "shell-local" {
+    inline = ["echo ${local.fruit} > ${local.fruit}.txt"]
+  }
+}

command/test-fixtures/var-arg/var-arg-tests/icecream.auto.pkrvrs.hcl

@@ -0,0 +1 @@
+fruit = "icecream"

command/test-fixtures/var-arg/var-arg-tests/peanut.auto.pkrvars.json

@@ -0,0 +1,3 @@
+{
+  "fruit": "peanut" 
+}

hcl2template/parser.go

@@ -210,39 +210,44 @@ func (p *Parser) Parse(filename string, varFiles []string, argVars map[string]st
 	{
 		hclVarFiles, jsonVarFiles, moreDiags := GetHCL2Files(filename, hcl2AutoVarFileExt, hcl2AutoVarJsonFileExt)
 		diags = append(diags, moreDiags...)
-		for _, file := range varFiles {
+
+		// Combine all variable files into a single list, preserving the intended precedence and order.
+		// The order is: auto-loaded HCL files, auto-loaded JSON files, followed by user-specified varFiles.
+		// This ensures that user-specified files can override values from auto-loaded files,
+		// and that their relative order is preserved exactly as specified by the user.
+		variableFileNames := append(append(hclVarFiles, jsonVarFiles...), varFiles...)
+
+		var variableFiles []*hcl.File
+
+		for _, file := range variableFileNames {
+			var (
+				f         *hcl.File
+				moreDiags hcl.Diagnostics
+			)
 			switch filepath.Ext(file) {
 			case ".hcl":
-				hclVarFiles = append(hclVarFiles, file)
+				f, moreDiags = p.ParseHCLFile(file)
 			case ".json":
-				jsonVarFiles = append(jsonVarFiles, file)
+				f, moreDiags = p.ParseJSONFile(file)
 			default:
-				diags = append(moreDiags, &hcl.Diagnostic{
-					Severity: hcl.DiagError,
-					Summary:  "Could not guess format of " + file,
-					Detail:   "A var file must be suffixed with `.hcl` or `.json`.",
-				})
+				moreDiags = hcl.Diagnostics{
+					&hcl.Diagnostic{
+						Severity: hcl.DiagError,
+						Summary:  "Could not guess format of " + file,
+						Detail:   "A var file must be suffixed with `.hcl` or `.json`.",
+					},
+				}
 			}
-		}
-		var varFiles []*hcl.File
-		for _, filename := range hclVarFiles {
-			f, moreDiags := p.ParseHCLFile(filename)
-			diags = append(diags, moreDiags...)
-			if moreDiags.HasErrors() {
-				continue
-			}
-			varFiles = append(varFiles, f)
-		}
-		for _, filename := range jsonVarFiles {
-			f, moreDiags := p.ParseJSONFile(filename)
+
 			diags = append(diags, moreDiags...)
 			if moreDiags.HasErrors() {
 				continue
 			}
-			varFiles = append(varFiles, f)
+			variableFiles = append(variableFiles, f)
+
 		}
 
-		diags = append(diags, cfg.collectInputVariableValues(os.Environ(), varFiles, argVars)...)
+		diags = append(diags, cfg.collectInputVariableValues(os.Environ(), variableFiles, argVars)...)
 	}
 
 	return cfg, diags