[DevTools] Preserve -Infinity in inspected values (facebook#36347)

## Summary

`getDataType` collapsed both `Infinity` and `-Infinity` to the
`'infinity'` data type, so a `-Infinity` value coming from inspected
props/state/hooks was rehydrated on the frontend as `Infinity`.

This adds a `'-infinity'` `DataType`, routes it through
`dehydrate`/`hydrate` alongside the existing `'infinity'` arm, and makes
`smartParse`/`smartStringify` (used for editable hook values) symmetric.

## Files

- `packages/react-devtools-shared/src/utils.js` — extend `DataType`,
split sign in `getDataType`, route `'-infinity'` through
`formatDataForPreview`.
- `packages/react-devtools-shared/src/hydration.js` — `dehydrate` and
`hydrate` cases for `'-infinity'`.
- `packages/react-devtools-shared/src/devtools/utils.js` — `smartParse`
accepts `'-Infinity'`; `smartStringify` returns `'-Infinity'` for
negative infinite values.
-
`packages/react-devtools-shared/src/__tests__/inspectedElement-test.js`
and `legacy/inspectElement-test.js` — added `minus_infinity={-Infinity}`
to the simple-data-types tests + snapshots.
-
`packages/react-devtools-shell/src/app/InspectableElements/SimpleValues.js`
— added `minusInfinity` to the dev shell so the path is exercised
manually.

## Test plan

- [x] `yarn prettier` / `yarn linc`
- [x] `yarn flow dom-node` — no errors
- [x] `yarn test --silent --no-watchman -t "should support simple data
types"` (source channel)
- [x] `yarn test-www --silent --no-watchman -t "should support simple
data types"` (www-modern)
- [ ] `yarn test-build-devtools` — relies on a built bundle; left to CI
per repo policy.

Fixes facebook#32552

Author: zxuhan

packages/react-devtools-shared/src/__tests__/inspectedElement-test.js

@@ -582,6 +582,7 @@ describe('InspectedElement', () => {
           boolean_false={false}
           boolean_true={true}
           infinity={Infinity}
+          minus_infinity={-Infinity}
           integer_zero={0}
           integer_one={1}
           float={1.23}
@@ -604,6 +605,7 @@ describe('InspectedElement', () => {
         "infinity": Infinity,
         "integer_one": 1,
         "integer_zero": 0,
+        "minus_infinity": -Infinity,
         "nan": NaN,
         "string": "abc",
         "string_empty": "",

packages/react-devtools-shared/src/__tests__/legacy/inspectElement-test.js

@@ -98,6 +98,7 @@ describe('InspectedElementContext', () => {
           boolean_false: false,
           boolean_true: true,
           infinity: Infinity,
+          minus_infinity: -Infinity,
           integer_zero: 0,
           integer_one: 1,
           float: 1.23,
@@ -128,6 +129,7 @@ describe('InspectedElementContext', () => {
           "infinity": Infinity,
           "integer_one": 1,
           "integer_zero": 0,
+          "minus_infinity": -Infinity,
           "nan": NaN,
           "string": "abc",
           "string_empty": "",

packages/react-devtools-shared/src/devtools/utils.js

@@ -235,6 +235,8 @@ export function smartParse(value: any): any | void | number {
   switch (value) {
     case 'Infinity':
       return Infinity;
+    case '-Infinity':
+      return -Infinity;
     case 'NaN':
       return NaN;
     case 'undefined':
@@ -249,7 +251,7 @@ export function smartStringify(value: any): string {
     if (Number.isNaN(value)) {
       return 'NaN';
     } else if (!Number.isFinite(value)) {
-      return 'Infinity';
+      return value > 0 ? 'Infinity' : '-Infinity';
     }
   } else if (value === undefined) {
     return 'undefined';

packages/react-devtools-shared/src/hydration.js

@@ -596,6 +596,7 @@ export function dehydrate(
       return value;
     }
     case 'infinity':
+    case '-infinity':
     case 'nan':
     case 'undefined':
       // Some values are lossy when sent through a WebSocket.
@@ -704,6 +705,8 @@ export function hydrate(
       return;
     } else if (value.type === 'infinity') {
       parent[last] = Infinity;
+    } else if (value.type === '-infinity') {
+      parent[last] = -Infinity;
     } else if (value.type === 'nan') {
       parent[last] = NaN;
     } else if (value.type === 'undefined') {

packages/react-devtools-shared/src/utils.js

@@ -708,6 +708,7 @@ export type DataType =
   | 'html_all_collection'
   | 'html_element'
   | 'infinity'
+  | '-infinity'
   | 'iterator'
   | 'opaque_iterator'
   | 'nan'
@@ -765,7 +766,7 @@ export function getDataType(data: Object): DataType {
       if (Number.isNaN(data)) {
         return 'nan';
       } else if (!Number.isFinite(data)) {
-        return 'infinity';
+        return data > 0 ? 'infinity' : '-infinity';
       } else {
         return 'number';
       }
@@ -1219,6 +1220,7 @@ export function formatDataForPreview(
     case 'boolean':
     case 'number':
     case 'infinity':
+    case '-infinity':
     case 'nan':
     case 'null':
     case 'undefined':

packages/react-devtools-shell/src/app/InspectableElements/SimpleValues.js

@@ -25,6 +25,7 @@ export default class SimpleValues extends Component {
         null={null}
         nan={NaN}
         infinity={Infinity}
+        minusInfinity={-Infinity}
         true={true}
         false={false}
         function={noop}