fix(environment): preserve null bodies and unique member matches (#10014)

src/application/environment/environmentCompareBody.test.ts

@@ -166,3 +166,25 @@ it.each([
     expect(requestBody(capture.records[0]!)).toEqual(expected);
   },
 );
+
+it.each([
+  ["null", null],
+  ["false", false],
+  ["0", 0],
+  ['""', ""],
+  ["not-json", "not-json"],
+] as const)(
+  "preserves the recorded request JSON value %s",
+  (text, expected) => {
+    const capture = environmentManifestCaptureFixture([
+      {
+        request: {
+          method: "POST",
+          url: "http://app.example/api/value",
+          postData: { mimeType: "application/json", text },
+        },
+      },
+    ]);
+    expect(requestBody(capture.records[0]!)).toEqual(expected);
+  },
+);

src/application/environment/environmentCompareDiff.ts

@@ -429,7 +429,9 @@ class Differ {
     for (const [key, value] of Object.entries(live)) {
       const child = `${pointer}/${escapePointer(key)}`;
       const other = envKey(key);
-      if (!Object.hasOwn(env, other))
+      // A translated key and a verbatim key may name the same entry; an
+      // environment member can account for only one live member.
+      if (!Object.hasOwn(env, other) || matched.has(other))
         this.add({
           category: "missing-field",
           pointer: child,

src/application/environment/environmentCompareIdsIntegration.test.ts

@@ -26,6 +26,25 @@ const compareRows = (
   return report.value.probes[0]!;
 };
 
+describe("environment comparison collection matching", () => {
+  it("does not match two live object keys to one environment entry", () => {
+    const probe = compareRows(
+      [
+        ["GET", "/api/items", [{ id: 1, name: "A" }]],
+        ["GET", "/api/counts", { counts: { "1": 5 } }],
+      ],
+      [
+        ["GET", "/api/items", [{ id: 101, name: "A" }]],
+        ["GET", "/api/counts", { counts: { "1": 5, "101": 5 } }],
+      ],
+    );
+    expect(probe.results.map((step) => step.equal)).toEqual([true, false]);
+    expect(probe.results[1]?.differences).toMatchObject([
+      { category: "missing-field", pointer: "/counts/101" },
+    ]);
+  });
+});
+
 describe("environment comparison identifier semantics", () => {
   it("reports changed business tokens and numeric arrays through the application comparison boundary", () => {
     const probe = compareRows(

src/application/environment/environmentCompareProbe.ts

@@ -78,9 +78,10 @@ export const requestBody = (
     return undefined;
   const { mimeType, text } = facts.postData;
   if (mimeType === undefined || text === undefined) return undefined;
-  return isJsonLike(mediaTypeEssence(mimeType))
-    ? (parseExactJson(text) ?? text)
-    : text;
+  const value = isJsonLike(mediaTypeEssence(mimeType))
+    ? parseExactJson(text)
+    : undefined;
+  return value === undefined ? text : value;
 };
 
 /** The application's answer as an environment answer carries it: JSON, text, or null when it is empty; a body the probe did not record is marked. */