plugin/discovery: Parse warnings from TF Registry

Terraform Registry (and other registry implementations) can now return
an array of warnings with the versions response. These warnings are now
displayed to the user during a `terraform init`.

command/plugins_test.go

@@ -197,7 +197,7 @@ func (i *mockProviderInstaller) PurgeUnused(map[string]discovery.PluginMeta) (di
 	return ret, nil
 }
 
-type callbackPluginInstaller func(provider string, req discovery.Constraints) (discovery.PluginMeta, error)
+type callbackPluginInstaller func(provider string, req discovery.Constraints) (discovery.PluginMeta, tfdiags.Diagnostics, error)
 
 func (cb callbackPluginInstaller) Get(provider string, req discovery.Constraints) (discovery.PluginMeta, tfdiags.Diagnostics, error) {
 	return cb(provider, req)

plugin/discovery/get.go

@@ -136,6 +136,17 @@ func (i *ProviderInstaller) Get(provider string, req Constraints) (PluginMeta, t
 		}
 		return PluginMeta{}, diags, ErrorNoSuchProvider
 	}
+
+	// Add any warnings from the response to diags
+	for _, warning := range allVersions.Warnings {
+		hostname, err := i.hostname()
+		if err != nil {
+			return PluginMeta{}, diags, err
+		}
+		diag := tfdiags.SimpleWarning(fmt.Sprintf("%s: %s", hostname, warning))
+		diags = diags.Append(diag)
+	}
+
 	if len(allVersions.Versions) == 0 {
 		return PluginMeta{}, diags, ErrorNoSuitableVersion
 	}
@@ -423,6 +434,16 @@ func (i *ProviderInstaller) getProviderChecksum(urls *response.TerraformProvider
 	return checksumForFile(shasums, urls.Filename), nil
 }
 
+func (i *ProviderInstaller) hostname() (string, error) {
+	provider := regsrc.NewTerraformProvider("", i.OS, i.Arch)
+	svchost, err := provider.SvcHost()
+	if err != nil {
+		return "", err
+	}
+
+	return svchost.ForDisplay(), nil
+}
+
 // list all versions available for the named provider
 func (i *ProviderInstaller) listProviderVersions(name string) (*response.TerraformProviderVersions, error) {
 	provider := regsrc.NewTerraformProvider(name, i.OS, i.Arch)

registry/response/terraform_provider.go

@@ -32,6 +32,7 @@ type TerraformProviderVersion struct {
 type TerraformProviderVersions struct {
 	ID       string                      `json:"id"`
 	Versions []*TerraformProviderVersion `json:"versions"`
+	Warnings []string                    `json:"warnings"`
 }
 
 // TerraformProviderPlatform is the Terraform-specific response structure for a