Diffs: add viewer payload validation and presentation defaults

extensions/diffs/src/config.test.ts

@@ -12,7 +12,10 @@ describe("resolveDiffsPluginDefaults", () => {
         defaults: {
           fontFamily: "JetBrains Mono",
           fontSize: 17,
+          lineSpacing: 1.8,
           layout: "split",
+          showLineNumbers: false,
+          diffIndicators: "classic",
           wordWrap: false,
           background: false,
           theme: "light",
@@ -22,11 +25,48 @@ describe("resolveDiffsPluginDefaults", () => {
     ).toEqual({
       fontFamily: "JetBrains Mono",
       fontSize: 17,
+      lineSpacing: 1.8,
       layout: "split",
+      showLineNumbers: false,
+      diffIndicators: "classic",
       wordWrap: false,
       background: false,
       theme: "light",
       mode: "view",
     });
   });
+
+  it("clamps and falls back for invalid line spacing and indicators", () => {
+    expect(
+      resolveDiffsPluginDefaults({
+        defaults: {
+          lineSpacing: -5,
+          diffIndicators: "unknown",
+        },
+      }),
+    ).toMatchObject({
+      lineSpacing: 1,
+      diffIndicators: "bars",
+    });
+
+    expect(
+      resolveDiffsPluginDefaults({
+        defaults: {
+          lineSpacing: 9,
+        },
+      }),
+    ).toMatchObject({
+      lineSpacing: 3,
+    });
+
+    expect(
+      resolveDiffsPluginDefaults({
+        defaults: {
+          lineSpacing: Number.NaN,
+        },
+      }),
+    ).toMatchObject({
+      lineSpacing: DEFAULT_DIFFS_TOOL_DEFAULTS.lineSpacing,
+    });
+  });
 });