util: honor breakLength Infinity with unlimited depth

Preserve single-line formatting for util.inspect() when breakLength is
Infinity and depth is unlimited, while keeping explicit compact settings
and customized defaultOptions.compact behavior unchanged.

Add regression coverage for depth: Infinity, depth: null, explicit
compact: 3, explicit compact: 1, and custom defaultOptions.compact.

Fixes: #60475

Author: Lellansin

lib/internal/util/inspect.js

@@ -2660,7 +2660,10 @@ function reduceToSingleString(
       // Consolidate all entries of the local most inner depth up to
       // `ctx.compact`, as long as the properties are smaller than
       // `ctx.breakLength`.
-      if (ctx.currentDepth - recurseTimes < ctx.compact &&
+      if (((ctx.breakLength === Infinity &&
+            (ctx.depth === Infinity || ctx.depth === null) &&
+            ctx.compact === 3) ||
+           ctx.currentDepth - recurseTimes < ctx.compact) &&
           entries === output.length) {
         // Line up all entries on a single line in case the entries do not
         // exceed `breakLength`. Add 10 as constant to start next to all other

test/parallel/test-util-inspect.js

@@ -1615,6 +1615,36 @@ if (typeof Symbol !== 'undefined') {
   assert.strictEqual(twoLines, "{\n  foo: 'abc',\n  bar: 'xyz'\n}");
 }
 
+{
+  const obj = {
+    a: {
+      b: {
+        c: {
+          d: 1,
+        },
+      },
+    },
+  };
+
+  assert.strictEqual(
+    util.inspect(obj, { breakLength: Infinity, depth: Infinity }),
+    '{ a: { b: { c: { d: 1 } } } }',
+  );
+  assert.strictEqual(
+    util.inspect(obj, { breakLength: Infinity, depth: null }),
+    '{ a: { b: { c: { d: 1 } } } }',
+  );
+  assert.strictEqual(
+    util.inspect(obj, { breakLength: Infinity, depth: Infinity, compact: 3 }),
+    '{ a: { b: { c: { d: 1 } } } }',
+  );
+
+  assert.strictEqual(
+    util.inspect(obj, { breakLength: Infinity, depth: Infinity, compact: 1 }),
+    '{\n  a: {\n    b: {\n      c: { d: 1 }\n    }\n  }\n}',
+  );
+}
+
 // util.inspect.defaultOptions tests.
 {
   const arr = new Array(101).fill();
@@ -1631,6 +1661,12 @@ if (typeof Symbol !== 'undefined') {
   assert.doesNotMatch(util.inspect(obj), /Object/);
   util.inspect.defaultOptions.depth = oldOptions.depth;
   assert.match(util.inspect(obj), /Object/);
+  util.inspect.defaultOptions.compact = 1;
+  assert.strictEqual(
+    util.inspect(obj, { breakLength: Infinity, depth: Infinity }),
+    '{\n  a: {\n    a: {\n      a: { a: 1 }\n    }\n  }\n}',
+  );
+  util.inspect.defaultOptions.compact = oldOptions.compact;
   assert.strictEqual(
     JSON.stringify(util.inspect.defaultOptions),
     JSON.stringify(oldOptions)