[nextest-runner] move miette JSON structs to test-helpers module

Going to use this for setup scripts soon.

nextest-runner/src/config/overrides.rs

@@ -757,24 +757,6 @@ mod tests {
         assert_eq!(overrides.retries(), RetryPolicy::new_without_delay(0));
     }
 
-    #[derive(Clone, Debug, Deserialize, Eq, PartialEq)]
-    struct MietteJsonReport {
-        message: String,
-        labels: Vec<MietteJsonLabel>,
-    }
-
-    #[derive(Clone, Debug, Deserialize, Eq, PartialEq)]
-    struct MietteJsonLabel {
-        label: String,
-        span: MietteJsonSpan,
-    }
-
-    #[derive(Clone, Debug, Deserialize, Eq, PartialEq)]
-    struct MietteJsonSpan {
-        offset: usize,
-        length: usize,
-    }
-
     #[test_case(
         indoc! {r#"
             [[profile.default.overrides]]

nextest-runner/src/config/test_helpers.rs

@@ -8,6 +8,7 @@ use crate::{
 };
 use camino::{Utf8Path, Utf8PathBuf};
 use guppy::{graph::PackageGraph, MetadataCommand};
+use serde::Deserialize;
 use std::{io::Write, path::PathBuf, process::Command};
 use target_spec::{Platform, TargetFeatures};
 
@@ -57,3 +58,21 @@ pub(super) fn custom_test_group(name: &str) -> CustomTestGroup {
     CustomTestGroup::new(name.into())
         .unwrap_or_else(|error| panic!("invalid custom test group {name}: {error}"))
 }
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq)]
+pub(super) struct MietteJsonReport {
+    pub(super) message: String,
+    pub(super) labels: Vec<MietteJsonLabel>,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq)]
+pub(super) struct MietteJsonLabel {
+    pub(super) label: String,
+    pub(super) span: MietteJsonSpan,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq)]
+pub(super) struct MietteJsonSpan {
+    pub(super) offset: usize,
+    pub(super) length: usize,
+}