String RegexMatches validator (#23)

Reference: #10

Author: ewbankkit

.changelog/23.txt

@@ -0,0 +1,3 @@
+```release-note:feature
+Introduced `stringvalidator.RegexMatches()` validation function
+```

stringvalidator/regex_matches.go

@@ -0,0 +1,64 @@
+package stringvalidator
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+
+	"github.com/hashicorp/terraform-plugin-framework-validators/validatordiag"
+	"github.com/hashicorp/terraform-plugin-framework/tfsdk"
+)
+
+var _ tfsdk.AttributeValidator = regexMatchesValidator{}
+
+// regexMatchesValidator validates that a string Attribute's value matches the specified regular expression.
+type regexMatchesValidator struct {
+	regexp  *regexp.Regexp
+	message string
+}
+
+// Description describes the validation in plain text formatting.
+func (validator regexMatchesValidator) Description(_ context.Context) string {
+	if validator.message != "" {
+		return validator.message
+	}
+	return fmt.Sprintf("value must match regular expression '%s'", validator.regexp)
+}
+
+// MarkdownDescription describes the validation in Markdown formatting.
+func (validator regexMatchesValidator) MarkdownDescription(ctx context.Context) string {
+	return validator.Description(ctx)
+}
+
+// Validate performs the validation.
+func (validator regexMatchesValidator) Validate(ctx context.Context, request tfsdk.ValidateAttributeRequest, response *tfsdk.ValidateAttributeResponse) {
+	s, ok := validateString(ctx, request, response)
+
+	if !ok {
+		return
+	}
+
+	if ok := validator.regexp.MatchString(s); !ok {
+		response.Diagnostics.Append(validatordiag.AttributeValueMatchesDiagnostic(
+			request.AttributePath,
+			validator.Description(ctx),
+			s,
+		))
+	}
+}
+
+// RegexMatches returns an AttributeValidator which ensures that any configured
+// attribute value:
+//
+//     - Is a string.
+//     - Matches the given regular expression https://github.com/google/re2/wiki/Syntax.
+//
+// Null (unconfigured) and unknown (known after apply) values are skipped.
+// Optionally an error message can be provided to return something friendlier
+// than "value must match regular expression 'regexp'".
+func RegexMatches(regexp *regexp.Regexp, message string) tfsdk.AttributeValidator {
+	return regexMatchesValidator{
+		regexp:  regexp,
+		message: message,
+	}
+}

stringvalidator/regex_matches_test.go

@@ -0,0 +1,65 @@
+package stringvalidator
+
+import (
+	"context"
+	"regexp"
+	"testing"
+
+	"github.com/hashicorp/terraform-plugin-framework/attr"
+	"github.com/hashicorp/terraform-plugin-framework/tfsdk"
+	"github.com/hashicorp/terraform-plugin-framework/types"
+	"github.com/hashicorp/terraform-plugin-go/tftypes"
+)
+
+func TestRegexMatchesValidator(t *testing.T) {
+	t.Parallel()
+
+	type testCase struct {
+		val         attr.Value
+		regexp      *regexp.Regexp
+		expectError bool
+	}
+	tests := map[string]testCase{
+		"not a String": {
+			val:         types.Bool{Value: true},
+			expectError: true,
+		},
+		"unknown String": {
+			val:    types.String{Unknown: true},
+			regexp: regexp.MustCompile(`^o[j-l]?$`),
+		},
+		"null String": {
+			val:    types.String{Null: true},
+			regexp: regexp.MustCompile(`^o[j-l]?$`),
+		},
+		"valid String": {
+			val:    types.String{Value: "ok"},
+			regexp: regexp.MustCompile(`^o[j-l]?$`),
+		},
+		"invalid String": {
+			val:         types.String{Value: "not ok"},
+			regexp:      regexp.MustCompile(`^o[j-l]?$`),
+			expectError: true,
+		},
+	}
+
+	for name, test := range tests {
+		name, test := name, test
+		t.Run(name, func(t *testing.T) {
+			request := tfsdk.ValidateAttributeRequest{
+				AttributePath:   tftypes.NewAttributePath().WithAttributeName("test"),
+				AttributeConfig: test.val,
+			}
+			response := tfsdk.ValidateAttributeResponse{}
+			RegexMatches(test.regexp, "").Validate(context.TODO(), request, &response)
+
+			if !response.Diagnostics.HasError() && test.expectError {
+				t.Fatal("expected error, got no error")
+			}
+
+			if response.Diagnostics.HasError() && !test.expectError {
+				t.Fatalf("got unexpected error: %s", response.Diagnostics)
+			}
+		})
+	}
+}

validatordiag/diag.go

@@ -26,6 +26,15 @@ func AttributeValueLengthDiagnostic(path *tftypes.AttributePath, description str
 	)
 }
 
+// AttributeValueMatchesDiagnostic returns an error Diagnostic to be used when an attribute's value has an invalid match.
+func AttributeValueMatchesDiagnostic(path *tftypes.AttributePath, description string, value string) diag.Diagnostic {
+	return diag.NewAttributeErrorDiagnostic(
+		path,
+		"Invalid Attribute Value Match",
+		capitalize(description)+", got: "+value,
+	)
+}
+
 // capitalize will uppercase the first letter in a UTF-8 string.
 func capitalize(str string) string {
 	if str == "" {