feat(promql): do not use regex for string labels (#7669)

In Prometheus, label values are treated as strings when used with the
`=` and `!=` operators, and as regular expressions when used with the
`=~` and `!~` operators.

Injecting and then highlighting all label values as regex leads to a
situation where entirely valid **string** label values containing regex
special characters are mistakenly parsed and highlighted as regex. This
results in syntax errors, causing labels to be highlighted incorrectly.

For example, in `foo{bar=~"[a-z]{1,3}"}`, `{` and `}` are regex special
characters, so regex highlighting is expected. However, in
`foo{path="/foo/{id}"}`, `{` and `}` are just part of the string and
have no special meaning, so the whole value should be highlighted as a
string.

6 files changed, 86 insertions, 2 deletions

diff --git a/queries/promql/highlights.scm b/queries/promql/highlights.scm
index 0f58f1578..a99fcdd05 100644
--- a/queries/promql/highlights.scm
+++ b/queries/promql/highlights.scm
@@ -36,7 +36,19 @@
 
 (label_name) @variable.member
 
-(label_value) @string.regexp
+((label_name)
+  [
+    "=~"
+    "!~"
+  ]
+  (label_value) @string.regexp)
+
+((label_name)
+  [
+    "="
+    "!="
+  ]
+  (label_value) @string)
 
 (function_name) @function.call
 
diff --git a/queries/promql/injections.scm b/queries/promql/injections.scm
index 4e7c1b261..791aba3d8 100644
--- a/queries/promql/injections.scm
+++ b/queries/promql/injections.scm
@@ -1,6 +1,11 @@
 ((comment) @injection.content
   (#set! injection.language "comment"))
 
-((label_value) @injection.content
+((label_name)
+  [
+    "=~"
+    "!~"
+  ]
+  (label_value) @injection.content
   (#set! injection.language "regex")
   (#offset! @injection.content 0 1 0 -1))
diff --git a/tests/query/highlights/promql/regex.promql b/tests/query/highlights/promql/regex.promql
new file mode 100644
index 000000000..fa61094a3
--- /dev/null
+++ b/tests/query/highlights/promql/regex.promql
@@ -0,0 +1,10 @@
+foo{path=~"^foo$"}[5m] or
+#          ^ @string.regexp
+foo{path!~"[a-zA-Z0-9]{1,3}"}[5m] or
+#          ^ @string.regexp
+foo{path="/api/users/{userId}"}[5m] or
+#         ^ @string
+foo{path!="/api/users/{userId}"}[5m]
+#          ^ @string
+
+# vim: ft=promql
diff --git a/tests/query/highlights/yaml/promql-on-prometheus-rules.yaml b/tests/query/highlights/yaml/promql-on-prometheus-rules.yaml
new file mode 100644
index 000000000..910405418
--- /dev/null
+++ b/tests/query/highlights/yaml/promql-on-prometheus-rules.yaml
@@ -0,0 +1,33 @@
+groups:
+- name: Hardware alerts
+  rules:
+  - alert: Node down
+    expr: up{job="node_exporter"} == 0
+    #     ^ @type
+    for: 3m
+    labels:
+      severity: warning
+    annotations:
+      title: Node {{ $labels.instance }} is down
+      description: Failed to scrape {{ $labels.job }} on {{ $labels.instance }} for more than 3 minutes. Node seems down.
+  - alert: Node down
+    expr: |
+      up{job="node_exporter"} == 0
+    # ^ @type
+    for: 3m
+    labels:
+      severity: warning
+  - alert: Regex and String matching
+    expr: |
+      foo{path=~"^foo$"}[5m] or foo{path!~"[a-zA-Z0-9]{1,3}"}[5m] or foo{path="/api/users/{userId}"}[5m] or foo{path!="/api/users/{userId}"}[5m]
+    # ^ @type
+    #            ^ @string.regexp
+    #                                      ^ @string.regexp
+    #                                                                          ^ @string
+    #                                                                                                                  ^ @string
+    for: 3m
+    labels:
+      severity: warning
+    annotations:
+      title: Foo
+      description: Bar
diff --git a/tests/query/injections/promql/regex.promql b/tests/query/injections/promql/regex.promql
new file mode 100644
index 000000000..08ed74640
--- /dev/null
+++ b/tests/query/injections/promql/regex.promql
@@ -0,0 +1,10 @@
+foo{path=~"^foo$"}[5m] or
+#          ^ @regex
+foo{path!~"[a-zA-Z0-9]{1,3}"}[5m] or
+#          ^ @regex
+foo{path="/api/users/{userId}"}[5m] or
+#         ^ @!regex
+foo{path!="/api/users/{userId}"}[5m]
+#          ^ @!regex
+
+# vim: ft=promql
diff --git a/tests/query/injections/yaml/promql-on-prometheus-rules.yaml b/tests/query/injections/yaml/promql-on-prometheus-rules.yaml
index f064da375..942fb1369 100644
--- a/tests/query/injections/yaml/promql-on-prometheus-rules.yaml
+++ b/tests/query/injections/yaml/promql-on-prometheus-rules.yaml
@@ -17,3 +17,17 @@ groups:
     for: 3m
     labels:
       severity: warning
+  - alert: Regex and String matching
+    expr: |
+      foo{path=~"^foo$"}[5m] or foo{path!~"[a-zA-Z0-9]{1,3}"}[5m] or foo{path="/api/users/{userId}"}[5m] or foo{path!="/api/users/{userId}"}[5m]
+    # ^ @promql
+    #            ^ @regex
+    #                                      ^ @regex
+    #                                                                          ^ @!regex
+    #                                                                                                                  ^ @!regex
+    for: 3m
+    labels:
+      severity: warning
+    annotations:
+      title: Foo
+      description: Bar