(GH-342) Implement CheckConfig in private processor

Prior to this commit, functional logic for validating a config file
lived not in the private processor (pct_config_processor) but in the
private build package as a private function.

This commit adds the CheckConfig function to the private processor
as a public function so that the private processor becomes a valid
implementation of the ConfigProcessorI interface.

It slightly refactors the implementation from the build package in
this transfer, as the logic for reading a configuration file is
already defined in a private function for the private processor. It
also ensures that the full path to the configuration file being checked
is returned in any error messages; the prior implementation only
specified 'pct-config.yml' which is neither generic for use in other
libraries/tools, nor specific if the caller is pointing to a config
anywhere but in the current working directory.

This commit **does not** replace any upstream package usage to point
to the new function, it **only** makes the private processor a valid
implementation of the ConfigProcessorI interface.

internal/pkg/pct_config_processor/pct_config_processor.go

@@ -29,6 +29,32 @@ func (p *PctConfigProcessor) ProcessConfig(sourceDir, targetDir string, force bo
 	return namespacedPath, nil
 }
 
+func (p *PctConfigProcessor) CheckConfig(configFile string) error {
+	info, err := p.readConfig(configFile)
+	if err != nil {
+		return err
+	}
+
+	msg := fmt.Sprintf("The following attributes are missing in %s:\n", configFile)
+	orig := msg
+	// These parts are essential for build and deployment.
+
+	if info.Template.Id == "" {
+		msg = msg + "  * id\n"
+	}
+	if info.Template.Author == "" {
+		msg = msg + "  * author\n"
+	}
+	if info.Template.Version == "" {
+		msg = msg + "  * version\n"
+	}
+	if msg != orig {
+		return fmt.Errorf(msg)
+	}
+
+	return nil
+}
+
 func (p *PctConfigProcessor) readConfig(configFile string) (info pct.PuppetContentTemplateInfo, err error) {
 	fileBytes, err := p.AFS.ReadFile(configFile)
 	if err != nil {

internal/pkg/pct_config_processor/pct_config_processor_test.go

@@ -2,6 +2,7 @@ package pct_config_processor_test
 
 import (
 	"path/filepath"
+	"regexp"
 	"testing"
 
 	"github.com/puppetlabs/pdkgo/internal/pkg/pct_config_processor"
@@ -100,3 +101,127 @@ template:
 	}
 
 }
+
+type CheckConfigTest struct {
+	name           string
+	mockConfigFile bool
+	configFilePath string
+	configFileYaml string
+	errorMsg       string
+}
+
+func TestPctConfigProcessor_CheckConfig(t *testing.T) {
+	type args struct {
+		configFile string
+	}
+	tests := []CheckConfigTest{
+		{
+			name:           "When config not found",
+			mockConfigFile: false,
+			configFilePath: "my/missing/pct-config.yml",
+			errorMsg:       "file does not exist",
+		},
+		{
+			name:           "When config valid",
+			mockConfigFile: true,
+			configFilePath: "my/valid/pct-config.yml",
+
+			configFileYaml: `---
+template:
+  id: test-template
+  author: test-user
+  version: 0.1.0
+`,
+			errorMsg: "",
+		},
+		{
+			name:           "When config invalid",
+			mockConfigFile: true,
+			configFilePath: "my/invalid/pct-config.yml",
+			// This is invalid because it starts with tabs which the parses errors on
+			configFileYaml: `---
+			foo: bar
+			`,
+			errorMsg: "parsing config: yaml",
+		},
+		{
+			name:           "When config missing author",
+			mockConfigFile: true,
+			configFilePath: "my/missing/author/pct-config.yml",
+
+			configFileYaml: `---
+template:
+  id: test-template
+  version: 0.1.0
+`,
+			errorMsg: `The following attributes are missing in .+:\s+\* author`,
+		},
+		{
+			name:           "When config missing id",
+			mockConfigFile: true,
+			configFilePath: "my/missing/id/pct-config.yml",
+
+			configFileYaml: `---
+template:
+  author: test-user
+  version: 0.1.0
+`,
+			errorMsg: `The following attributes are missing in .+:\s+\* id`,
+		},
+		{
+			name:           "When config missing version",
+			mockConfigFile: true,
+			configFilePath: "my/missing/version/pct-config.yml",
+
+			configFileYaml: `---
+template:
+  author: test-user
+  id: test-template
+`,
+			errorMsg: `The following attributes are missing in .+:\s+\* version`,
+		},
+		{
+			name:           "When config missing author, id, and version",
+			mockConfigFile: true,
+			configFilePath: "my/missing/version/pct-config.yml",
+
+			configFileYaml: `---
+template:
+`,
+			errorMsg: `The following attributes are missing in .+:\s+\* id\s+\* author\s+\* version`,
+		},
+		{
+			name:           "When config missing template key",
+			mockConfigFile: true,
+			configFilePath: "my/missing/version/pct-config.yml",
+
+			configFileYaml: `---
+foo: bar
+`,
+			errorMsg: `The following attributes are missing in .+:\s+\* id\s+\* author\s+\* version`,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			fs := afero.NewMemMapFs()
+			afs := &afero.Afero{Fs: fs}
+
+			if tt.mockConfigFile {
+				dir := filepath.Dir(tt.configFilePath)
+				afs.Mkdir(dir, 0750)                       //nolint:gosec,errcheck // this result is not used in a secure application
+				config, _ := afs.Create(tt.configFilePath) //nolint:gosec,errcheck // this result is not used in a secure application
+				config.Write([]byte(tt.configFileYaml))    //nolint:errcheck
+			}
+
+			configProcessor := pct_config_processor.PctConfigProcessor{AFS: afs}
+
+			err := configProcessor.CheckConfig(tt.configFilePath)
+
+			if tt.errorMsg != "" && err != nil {
+				assert.Regexp(t, regexp.MustCompile(tt.errorMsg), err.Error())
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}