From 5ced8c3c382bd947db2325689938321a2f63bf16 Mon Sep 17 00:00:00 2001
From: Pedro Tanaka <pedro.tanaka@shopify.com>
Date: Mon, 6 May 2024 16:12:57 +0200
Subject: [PATCH] Treating promql validation from ParseExpr

Signed-off-by: Pedro Tanaka <pedro.tanaka@shopify.com>
---
 pkg/extpromql/parser.go          | 21 ++++++++++++++++-----
 pkg/extpromql/parser_test.go     |  4 ++++
 pkg/store/storepb/custom_test.go |  3 ++-
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/pkg/extpromql/parser.go b/pkg/extpromql/parser.go
index 5284e5e9f3..1a43fd8a05 100644
--- a/pkg/extpromql/parser.go
+++ b/pkg/extpromql/parser.go
@@ -5,7 +5,9 @@ package extpromql
 
 import (
 	"fmt"
+	"strings"
 
+	"github.com/pkg/errors"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/promql/parser"
 
@@ -22,23 +24,22 @@ func ParseExpr(input string) (parser.Expr, error) {
 // ParseMetricSelector parses the provided textual metric selector into a list of
 // label matchers.
 func ParseMetricSelector(input string) ([]*labels.Matcher, error) {
-	// Parse the input string as a PromQL expression.
 	expr, err := ParseExpr(input)
-	if err != nil {
+	// because of the AST checking present in the ParseExpr function,
+	// we need to ignore the error if it is just the check for empty name matcher.
+	if err != nil && !isEmptyNameMatcherErr(err) {
 		return nil, err
 	}
 
-	// The type of the expression should be *parser.VectorSelector.
 	vs, ok := expr.(*parser.VectorSelector)
 	if !ok {
 		return nil, fmt.Errorf("expected type *parser.VectorSelector, got %T", expr)
 	}
 
-	// Convert the label matchers from the vector selector to the desired type.
 	matchers := make([]*labels.Matcher, len(vs.LabelMatchers))
 	for i, lm := range vs.LabelMatchers {
 		matchers[i] = &labels.Matcher{
-			Type:  labels.MatchType(lm.Type),
+			Type:  lm.Type,
 			Name:  lm.Name,
 			Value: lm.Value,
 		}
@@ -46,3 +47,13 @@ func ParseMetricSelector(input string) ([]*labels.Matcher, error) {
 
 	return matchers, nil
 }
+
+func isEmptyNameMatcherErr(err error) bool {
+	var parseErrs parser.ParseErrors
+	if errors.As(err, &parseErrs) {
+		return len(parseErrs) == 1 &&
+			strings.HasSuffix(parseErrs[0].Error(), "vector selector must contain at least one non-empty matcher")
+	}
+
+	return false
+}
diff --git a/pkg/extpromql/parser_test.go b/pkg/extpromql/parser_test.go
index 1c0cfebdcd..72ef7b26cb 100644
--- a/pkg/extpromql/parser_test.go
+++ b/pkg/extpromql/parser_test.go
@@ -39,6 +39,10 @@ func TestParseMetricSelector(t *testing.T) {
 			name:  "multiple selectors with regex",
 			input: `http_requests_total{method="GET",code=~"2.*"}`,
 		},
+		{
+			name:  "selector with negative regex",
+			input: `{code!~"2.*"}`,
+		},
 	}
 
 	for _, tc := range testCases {
diff --git a/pkg/store/storepb/custom_test.go b/pkg/store/storepb/custom_test.go
index 91e2a1a669..4a1c6d83c2 100644
--- a/pkg/store/storepb/custom_test.go
+++ b/pkg/store/storepb/custom_test.go
@@ -15,6 +15,7 @@ import (
 	"github.com/prometheus/prometheus/tsdb/chunkenc"
 
 	"github.com/efficientgo/core/testutil"
+
 	"github.com/thanos-io/thanos/pkg/extpromql"
 	"github.com/thanos-io/thanos/pkg/store/labelpb"
 )
@@ -521,7 +522,7 @@ func TestMatchersToString_Translate(t *testing.T) {
 
 			// Is this parsable?
 			promMsParsed, err := extpromql.ParseMetricSelector(c.expected)
-			testutil.Ok(t, err)
+			testutil.Ok(t, err, "unexpected error parsing %q", c.expected)
 			testutil.Assert(t, len(promMs) == len(promMsParsed))
 			for i := 0; i < len(promMs); i++ {
 				testutil.Equals(t, promMs[i].String(), promMsParsed[i].String())