config: disallow names starting with ints

Fixes #10597

This disallows any names for variables, modules, etc. starting with
ints. This causes parse errors with the new HIL parser and actually
causes long term ambiguities if we allow this.

I've also updated the upgrade guide to note this as a backwards
compatibility and how people can fix this going forward.

config/config.go

@@ -18,7 +18,7 @@ import (
 
 // NameRegexp is the regular expression that all names (modules, providers,
 // resources, etc.) must follow.
-var NameRegexp = regexp.MustCompile(`\A[A-Za-z0-9\-\_]+\z`)
+var NameRegexp = regexp.MustCompile(`(?i)\A[A-Z_][A-Z0-9\-\_]+\z`)
 
 // Config is the configuration that comes from loading a collection
 // of Terraform templates.
@@ -282,6 +282,14 @@ func (c *Config) Validate() error {
 		varMap[v.Name] = v
 	}
 
+	for k, _ := range varMap {
+		if !NameRegexp.MatchString(k) {
+			errs = append(errs, fmt.Errorf(
+				"variable %q: variable name must match regular expresion %s",
+				k, NameRegexp))
+		}
+	}
+
 	for _, v := range c.Variables {
 		if v.Type() == VariableTypeUnknown {
 			errs = append(errs, fmt.Errorf(

config/loader_hcl.go

@@ -404,6 +404,11 @@ func loadVariablesHcl(list *ast.ObjectList) ([]*Variable, error) {
 		}
 
 		n := item.Keys[0].Token.Value().(string)
+		if !NameRegexp.MatchString(n) {
+			return nil, fmt.Errorf(
+				"position %s: 'variable' name must match regular expression: %s",
+				item.Pos(), NameRegexp)
+		}
 
 		/*
 			// TODO: catch extra fields

config/loader_test.go

@@ -447,6 +447,20 @@ func TestLoadFile_variables(t *testing.T) {
 	}
 }
 
+func TestLoadFile_varInt(t *testing.T) {
+	_, err := LoadFile(filepath.Join(fixtureDir, "var_int.tf"))
+	if err == nil {
+		t.Fatal("should have error")
+	}
+}
+
+func TestLoadFile_varIntBare(t *testing.T) {
+	_, err := LoadFile(filepath.Join(fixtureDir, "var_int_bare.tf"))
+	if err == nil {
+		t.Fatal("should have error")
+	}
+}
+
 func TestLoadDir_basic(t *testing.T) {
 	dir := filepath.Join(fixtureDir, "dir-basic")
 	c, err := LoadDir(dir)

config/test-fixtures/var_int.tf

@@ -0,0 +1 @@
+variable "1x1" {}

config/test-fixtures/var_int_bare.tf

@@ -0,0 +1 @@
+variable 1x1 {}