validate that modules name providers passed to mod

Passing a provider into a module requires that it be named within the
module. This would previously pass validation, however core would fail
to resolve the provider resulting in an unclear "provider not found"
error.

configs/provider_validation.go

@@ -23,9 +23,11 @@ import (
 // noProviderConfig argument is passed down the call stack, indicating that the
 // module call, or a parent module call, has used a feature that precludes
 // providers from being configured at all within the module.
-func validateProviderConfigs(call *ModuleCall, cfg *Config, noProviderConfig bool) (diags hcl.Diagnostics) {
+func validateProviderConfigs(parentCall *ModuleCall, cfg *Config, noProviderConfig bool) (diags hcl.Diagnostics) {
+	mod := cfg.Module
+
 	for name, child := range cfg.Children {
-		mc := cfg.Module.ModuleCalls[name]
+		mc := mod.ModuleCalls[name]
 
 		// if the module call has any of count, for_each or depends_on,
 		// providers are prohibited from being configured in this module, or
@@ -34,11 +36,6 @@ func validateProviderConfigs(call *ModuleCall, cfg *Config, noProviderConfig boo
 		diags = append(diags, validateProviderConfigs(mc, child, nope)...)
 	}
 
-	// nothing else to do in the root module
-	if call == nil {
-		return diags
-	}
-
 	// the set of provider configuration names passed into the module, with the
 	// source range of the provider assignment in the module call.
 	passedIn := map[string]PassedProviderConfig{}
@@ -59,13 +56,6 @@ func validateProviderConfigs(call *ModuleCall, cfg *Config, noProviderConfig boo
 	// their provider types.
 	localNames := map[string]addrs.AbsProviderConfig{}
 
-	for _, passed := range call.Providers {
-		name := providerName(passed.InChild.Name, passed.InChild.Alias)
-		passedIn[name] = passed
-	}
-
-	mod := cfg.Module
-
 	for _, pc := range mod.ProviderConfigs {
 		name := providerName(pc.Name, pc.Alias)
 		// Validate the config against an empty schema to see if it's empty.
@@ -95,6 +85,76 @@ func validateProviderConfigs(call *ModuleCall, cfg *Config, noProviderConfig boo
 		}
 	}
 
+	// collect providers passed from the parent
+	if parentCall != nil {
+		for _, passed := range parentCall.Providers {
+			name := providerName(passed.InChild.Name, passed.InChild.Alias)
+			passedIn[name] = passed
+		}
+	}
+
+	parentModuleText := "the root module"
+	moduleText := "the root module"
+	if !cfg.Path.IsRoot() {
+		moduleText = cfg.Path.String()
+		if parent := cfg.Path.Parent(); !parent.IsRoot() {
+			// module address are prefixed with `module.`
+			parentModuleText = parent.String()
+		}
+	}
+
+	// Verify that any module calls only refer to named providers, and that
+	// those providers will have a configuration at runtime. This way we can
+	// direct users where to add the missing configuration, because the runtime
+	// error is only "missing provider X".
+	for _, modCall := range mod.ModuleCalls {
+		for _, passed := range modCall.Providers {
+			// aliased providers are handled more strictly, and are never
+			// inherited, so they are validated within modules further down.
+			// Skip these checks to prevent redundant diagnostics.
+			if passed.InParent.Alias != "" {
+				continue
+			}
+
+			name := passed.InParent.String()
+			_, confOK := configured[name]
+			_, localOK := localNames[name]
+			_, passedOK := passedIn[name]
+
+			// This name was not declared somewhere within in the
+			// configuration. We ignore empty configs, because they will
+			// already produce a warning.
+			if !(confOK || localOK) {
+				diags = append(diags, &hcl.Diagnostic{
+					Severity: hcl.DiagWarning,
+					Summary:  fmt.Sprintf("Provider %s is undefined", name),
+					Detail: fmt.Sprintf("No provider named %s has been declared in %s.\n", name, moduleText) +
+						fmt.Sprintf("If you wish to refer to the %s provider within the module, add a provider configuration, or an entry in the required_providers block.", name),
+					Subject: &passed.InParent.NameRange,
+				})
+				continue
+			}
+
+			// Now we may have named this provider within the module, but
+			// there won't be a configuration available at runtime if the
+			// parent module did not pass one in.
+			if !cfg.Path.IsRoot() && !(confOK || passedOK) {
+				diags = append(diags, &hcl.Diagnostic{
+					Severity: hcl.DiagWarning,
+					Summary:  fmt.Sprintf("No configuration passed in for provider %s in %s", name, cfg.Path),
+					Detail: fmt.Sprintf("Provider %s is referenced within %s, but no configuration has been supplied.\n", name, moduleText) +
+						fmt.Sprintf("Add a provider named %s to the providers map for %s in %s.", name, cfg.Path, parentModuleText),
+					Subject: &passed.InParent.NameRange,
+				})
+			}
+		}
+	}
+
+	if cfg.Path.IsRoot() {
+		// nothing else to do in the root module
+		return diags
+	}
+
 	// there cannot be any configurations if no provider config is allowed
 	if len(configured) > 0 && noProviderConfig {
 		diags = append(diags, &hcl.Diagnostic{
@@ -129,8 +189,9 @@ func validateProviderConfigs(call *ModuleCall, cfg *Config, noProviderConfig boo
 		diags = append(diags, &hcl.Diagnostic{
 			Severity: hcl.DiagError,
 			Summary:  fmt.Sprintf("No configuration for provider %s", name),
-			Detail:   fmt.Sprintf("Configuration required for %s.", providerAddr),
+			Detail: fmt.Sprintf("Configuration required for %s.\n", providerAddr) +
-			Subject:  &call.DeclRange,
+				fmt.Sprintf("Add a provider named %s to the providers map for %s in %s.", name, cfg.Path, parentModuleText),
+			Subject: &parentCall.DeclRange,
 		})
 	}
 
@@ -240,10 +301,6 @@ func validateProviderConfigs(call *ModuleCall, cfg *Config, noProviderConfig boo
 		})
 	}
 
-	if diags.HasErrors() {
-		return diags
-	}
-
 	return diags
 }
 

configs/testdata/config-diagnostics/pass-inherited-provider/main.tf

@@ -0,0 +1,7 @@
+provider "test" {
+  value = "ok"
+}
+
+module "mod" {
+  source = "./mod"
+}

configs/testdata/config-diagnostics/pass-inherited-provider/mod/main.tf

@@ -0,0 +1,17 @@
+terraform {
+  required_providers {
+    test = {
+      source = "hashicorp/test"
+    }
+  }
+}
+
+module "mod2" {
+  source = "./mod2"
+
+  // the test provider is named here, but a config must be supplied from the
+  // parent module.
+  providers = {
+    test.foo = test
+  }
+}

configs/testdata/config-diagnostics/pass-inherited-provider/mod2/main.tf

@@ -0,0 +1,12 @@
+terraform {
+  required_providers {
+    test = {
+      source = "hashicorp/test"
+      configuration_aliases = [test.foo]
+    }
+  }
+}
+
+resource "test_resource" "foo" {
+  provider = test.foo
+}

configs/testdata/config-diagnostics/pass-inherited-provider/warnings

@@ -0,0 +1 @@
+pass-inherited-provider/mod/main.tf:15,16-20: No configuration passed in for provider test in module.mod; Provider test is referenced within module.mod, but no configuration has been supplied

configs/testdata/config-diagnostics/unknown-root-provider/main.tf

@@ -0,0 +1,7 @@
+module "mod" {
+  source = "./mod"
+  providers = {
+    // bar may be required by the module, but the name is not defined here
+    bar = bar
+  }
+}

configs/testdata/config-diagnostics/unknown-root-provider/mod/main.tf

@@ -0,0 +1,10 @@
+terraform {
+  required_providers {
+    bar = {
+      version = "~>1.0.0"
+    }
+  }
+}
+
+resource "bar_resource" "x" {
+}

configs/testdata/config-diagnostics/unknown-root-provider/warnings

@@ -0,0 +1 @@
+unknown-root-provider/main.tf:5,11-14: Provider bar is undefined; No provider named bar has been declared in the root module