Explicit coding rules (#1772)

## Context

Some coding styles are unwritten and not covered by eslint.

## Proposed solution

Explicit them for now, let's discuss on them.

Once this PR is merged, we will be able to later work on writing Eslint
rules when possible and remove the associated coding styles from the
documentation.

## Has this been tested?

<!-- Put an `x` in the box that applies: -->

- [ ] 👍 yes, I added tests to the test suite
- [ ] 💭 no, because this PR is a draft and still needs work
- [x] 🙅 no, because this is not relevant here
- [ ] 🙋 no, because I need help <!-- Detail how we can help you -->

Author: fflorent

documentation/develop.md

@@ -110,6 +110,139 @@ $ yarn start:debug
 
 And start using your nodejs debugger client (like the Chrome Devtools). See https://nodejs.org/en/docs/guides/debugging-getting-started#inspector-clients
 
+
+## Coding Rules
+
+Most of the coding rules are already enforced by the Eslint tool. You can run it using the `yarn lint:ci` command 
+and you may `yarn lint:fix` to make eslint try to fix them for you.
+
+There are still few rules that are not yet configured in Eslint (we plan to add them):
+
+### Regarding the imports
+- The import should be gathered by these blocks following this order:
+  - The modules of the projects
+  - The contribs and the native libraries (ideally the later prefixed with `node:`);
+  - Separate the blocks with a new line
+```ts
+// ✅ Good
+import {
+  ExternalStorage,
+  joinKeySegments,
+} from 'app/server/lib/ExternalStorage';
+import {MemoryWritableStream} from 'app/server/utils/streams';
+
+import * as fse from 'fs-extra';
+import * as stream from 'node:stream';
+import * as path from 'path';
+
+// ❌ Bad
+import {
+  ExternalStorage,
+  joinKeySegments,
+} from 'app/server/lib/ExternalStorage';
+import * as path from 'path';
+import * as fse from 'fs-extra';
+import * as stream from 'node:stream';
+import {MemoryWritableStream} from 'app/server/utils/streams';
+
+```
+- Their paths should be absolute (ie. start with `app/`, `test/`, ... and not with `./`) and should not contain the extension:
+
+```ts
+// ✅ Good
+import {Sessions} from 'app/server/lib/Sessions';
+import {TcpForwarder} from 'test/server/tcpForwarder';
+import * as testUtils from 'test/server/testUtils';
+
+// ❌ Bad
+import {Sessions} from '../../app/server/lib/Sessions'
+import {TcpForwarder} from './tcpForwarder';
+import * as testUtils from 'test/server/testUtils.ts';
+```
+
+
+- They should be alphabetically sorted by the order of the import path within their blocks:
+```ts
+// ✅ Good
+
+import {
+  ExternalStorage,
+  joinKeySegments,
+} from 'app/server/lib/ExternalStorage';
+import {drainWhenSettled, MemoryWritableStream} from 'app/server/utils/streams';
+
+// ❌ Bad (`app/server/utils` comes after `apps/server/lib`)
+
+import {drainWhenSettled, MemoryWritableStream} from 'app/server/utils/streams';
+import {
+  ExternalStorage,
+  joinKeySegments,
+} from 'app/server/lib/ExternalStorage';
+```
+
+### Spacing
+
+```ts
+// ✅ Good :
+// - no space after the function name (`foo`)
+// - one space before the opening curly brace (`{`);
+// - no space before the colon (`:`)
+// - one space after the colon (`:`)
+// - one space around the equal (`=`) sign
+
+function foo(varName: Type) {
+  const myOtherVar = varName;
+}
+
+// ❌ Bad
+function foo (varName :Type){
+  const myOtherVar=varName;
+}
+```
+
+### Strings
+
+```ts
+import {makeT, t} from 'app/client/lib/localization';
+
+const t = makeT('MyModule');
+
+// ✅ Good :
+// - Following local rules: either choose simple quotes or double quotes
+// - use the `t()` function (client-side) or `req.t()` function (server-side) for the texts that will be displayed to the user and therefore needs localization
+// - pass arguments to the `t()` function, does not use concatenation for the localizers
+// - does not concatenate nor use the template strings for the `t()` function, but do as below
+// - consistency of the use of type of quotes locally (`"` or `'`) within a same function, except for concatenation where template strings are allowed
+
+function foo() {
+  const str1 = "foo";
+  const str2 = "bar";
+  const shortLocalizedStr = t("Lorem Ipsum");
+  const result = someFunction();
+  // Passing arguments
+  const localizedStrWithPlaceholder = t("Your response: {{result}}", {result});
+  // Because we use i18next-scanner to collect the translated strings, we have to
+  // use either simple or double quotes and end lines with backslashes (`\`) to insert a new line.
+  // Unfortunately this library does not support template strings nor concatenation.
+  // See: https://github.com/i18next/i18next-scanner/issues/35
+  const localizedStr = t("Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed non risus. \
+Suspendisse lectus tortor, dignissim sit amet, adipiscing nec, ultricies sed, dolor. \
+Cras elementum ultrices diam. Maecenas ligula massa, varius a, semper congue, euismod non, mi.");
+}
+
+// ❌ Bad
+function foo() {
+  const str1 = 'foo';
+  const str2 = "bar";
+  const localizedStrWithPlaceholder = t("Your response: " + someFunction());
+  // These concatenations will cause our tool to collect string miss this translation key.
+  const localizedStr = t("Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed non risus. " +
+    "Suspendisse lectus tortor, dignissim sit amet, adipiscing nec, ultricies sed, dolor. " +
+    "Cras elementum ultrices diam. Maecenas ligula massa, varius a, semper congue, euismod non, mi.");
+}
+```
+
+
 ## Run tests
 
 You may run the tests using one of these commands: