## Decision

The *Build Tool Team* has decided to use Architectural Decision Records (aka ADR) to track decisions we want to follow.

The main logic with ADRs is to describe (architectural) decisions made:

* To provide best practices and solutions we (as the *build tool* team) want to promote.
* To avoid asking the same thing multiple times during code review.

All the dependencies we have seen are a fixed function or class.

But there could be cases where you want to be able to set parameters on the dependency, without having to declare many different functions or classes.

Let's imagine that we want to have a dependency that checks if the query parameter `q` contains some fixed content.

But we want to be able to parameterize that fixed content.

## A "callable" instance

			want, err := readFile(outPath)
			if err != nil {
				t.Fatal(err)
			}

			if got != want {
				diff, err := compare.ManifestDiffWithRenameSelectIgnore(got, want,
					"", diffSelect, tt.diffIgnore, false)
				if err != nil {
					t.Fatal(err)
				}
				if diff != "" {
					t.Fatalf("%s: got:\n%s\nwant:\n%s\n(-got, +want)\n%s\n", tt.desc, "", "", diff)
				}

	wantJSON, err := readFile(goldenFilepath)
	if err != nil {
		t.Fatal(err)
	}

	var want, got []byte
	if got, err = yaml.JSONToYAML([]byte(gotJSON)); err != nil {
		t.Fatal(err)
	}
	if want, err = yaml.JSONToYAML([]byte(wantJSON)); err != nil {
		t.Fatal(err)
	}

	if diff := util.YAMLDiff(string(want), string(got)); diff != "" {
		t.Fatalf("diff: %s", diff)
	}
}

		err := tryParse(t, func() {
			parser.Parse()
		})

		switch {
		case err == nil:
			t.Errorf("#%d: %q: want error %q; have none", i, test.input, test.error)
		case !strings.Contains(err.Error(), test.error):
			t.Errorf("#%d: %q: want error %q; have %q", i, test.input, test.error, err)
		}
	}

				failOnErr(err)
				_, err = hash.Write(data)
				failOnErr(err)
				got[conf] = map[ErasureAlgo]uint64{algo: hash.Sum64()}
			}

			if a, b := want[conf], got[conf]; !reflect.DeepEqual(a, b) {
				fmt.Fprintf(os.Stderr, "%v: error on self-test [d:%d,p:%d]: want %#v, got %#v\n", algo, conf[0], conf[1], a, b)
				ok = false
				continue
			}
			// Delete first shard and reconstruct...
			first := encoded[0]

	for _, v := range headers {
		req := &http.Request{
			Header: http.Header{
				v.key: []string{v.val},
			},
		}
		res := GetSourceScheme(req)
		if res != v.expected {
			t.Errorf("wrong header for %s: got %s want %s", v.key, res,
				v.expected)
		}
	}
}

// TestGetSourceIP - check the source ip of a request is parsed correctly.
func TestGetSourceIP(t *testing.T) {
	headers := []headerTest{

func bitrotVerify(r io.Reader, wantSize, partSize int64, algo BitrotAlgorithm, want []byte, shardSize int64) error {
	if algo != HighwayHash256S {
		h := algo.New()
		if n, err := io.Copy(h, r); err != nil || n != wantSize {
			// Premature failure in reading the object, file is corrupt.
			return errFileCorrupt
		}
		if !bytes.Equal(h.Sum(nil), want) {
			return errFileCorrupt
		}
		return nil
	}

In some cases, you may want to override the logic used by the `Request` and `APIRoute` classes.

In particular, this may be a good alternative to logic in a middleware.

For example, if you want to read or manipulate the request body before it is processed by your application.

!!! danger
    This is an "advanced" feature.

    If you are just starting with **FastAPI** you might want to skip this section.

## Use cases

For example, let's say that you want to use <a href="https://github.com/ijl/orjson" class="external-link" target="_blank">`orjson`</a>, but with some custom settings not used in the included `ORJSONResponse` class.

Let's say you want it to return indented and formatted JSON, so you want to use the orjson option `orjson.OPT_INDENT_2`.