//
		// This differs from os.WriteFile, which truncates to 0 *before* writing
		// via os.O_TRUNC. Truncating only after writing ensures that a second write
		// of the same content to the same file is idempotent, and does not — even
		// temporarily! — undo the effect of the first write.
		err = f.Truncate(int64(len(entry)))
	}
	if closeErr := f.Close(); err == nil {
		err = closeErr
	}
	if err != nil {

  // if the object being admitted is modified by other admission plugins after the initial webhook call.
  // Webhooks that specify this option *must* be idempotent, able to process objects they previously admitted.
  // Note:
  // * the number of additional invocations is not guaranteed to be exactly one.

			if actual != tc.want {
				t.Fatalf("Unexpected result.\nExpected:\n%v\nActual:\n%v", tc.want, actual)
			}
			t.Run("idempotency", func(t *testing.T) {
				actual := appendMultusNetwork(actual, "istio-cni")
				if actual != tc.want {
					t.Fatalf("Function is not idempotent.\nExpected:\n%v\nActual:\n%v", tc.want, actual)
				}
			})
		})
	}
}

func Test_updateClusterEnvs(t *testing.T) {

There are also some constraints and possible limitations.

[[sec:constrained_syntax]]
==== Constrained Syntax

The `plugins {}` block does not support arbitrary code.

It is constrained to be idempotent (produce the same result every time) and side effect-free (safe for Gradle to execute at any time).

The form is:

====
[.multi-language-sample]
=====
.build.gradle.kts
[source,kotlin]
----

			req:  &Request{Method: "POST", Header: Header{"Idempotency-Key": {"x"}}},
			want: true,
		},
		{
			name: "POST_x-idempotency-key",
			req:  &Request{Method: "POST", Header: Header{"X-Idempotency-Key": {"x"}}},
			want: true,
		},
		{
			name: "POST_body",
			req:  &Request{Method: "POST", Header: Header{"Idempotency-Key": {"x"}}, Body: someBody},
			want: false,
		},
	}

	// thread B and did not need to execute the syscall, but did anyway
	// because doAllThreadsSyscall could not be sure whether it was
	// required.
	//
	// Some system calls may not be idempotent, so we ensure each thread
	// executes the system call exactly once.
	for mp := allm; mp != nil; mp = mp.alllink {
		for atomic.Load64(&mp.procid) == 0 {
			// Thread is starting.
			osyield()
		}
	}

	// Unreserve is called by the scheduling framework when a reserved pod was
	// rejected, an error occurred during reservation of subsequent plugins, or
	// in a later phase. The Unreserve method implementation must be idempotent
	// and may be called by the scheduler even if the corresponding Reserve
	// method for the same plugin was not called.
	Unreserve(ctx context.Context, state *CycleState, p *v1.Pod, nodeName string)
}

// mounting, or unmounting a volume that are executed with a NewNestedPendingOperations which
// prevents more than one operation from being triggered on the same volume.
//
// These operations should be idempotent (for example, AttachVolume should
// still succeed if the volume is already attached to the node, etc.). However,
// they depend on the volume plugins to implement this behavior.
//

	return s.muxAndDiscoveryCompleteSignals
}

// RegisterDestroyFunc registers a function that will be called during Destroy().
// The function have to be idempotent and prepared to be called more than once.
func (s *GenericAPIServer) RegisterDestroyFunc(destroyFn func()) {
	s.destroyFns = append(s.destroyFns, destroyFn)
}

}

// Close - calls the cleanup actions in reverse order
func (g *GetObjectReader) Close() error {
	if g == nil {
		return nil
	}
	// sync.Once is used here to ensure that Close() is
	// idempotent.
	g.once.Do(func() {
		for i := len(g.cleanUpFns) - 1; i >= 0; i-- {
			g.cleanUpFns[i]()
		}
	})
	return nil
}

// compressionIndexEncrypter returns a function that will read data from input,