Add three new front-end coding standards

engineering/architecture/front-end-standards.md

@@ -10,7 +10,9 @@ dateCreated: 2022-01-14T19:02:19.924Z
 
 # Front end code standards
 
-## Naming conventions
+## General
+
+### Naming conventions
 
 * File names for Components, Classes and Stylesheets should be in PascalCase. Examples:
 
@@ -79,7 +81,92 @@ dateCreated: 2022-01-14T19:02:19.924Z
 
     - [discussion](https://github.com/centerofci/mathesar/discussions/872)
 
-## `null` vs `undefined`
+## HTML
+
+### Build components for valid DOM nesting
+
+When working inside a component that _might_ be placed where [phrasing content](https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Content_categories#phrasing_content) is required, be sure to only use phrasing content elements (like `span`) instead of _not_-phrasing content elements (like `div`).
+
+-  ✅ Good
+
+    `FancyCheckbox.svelte`
+
+    ```ts
+    <span class="make-it-fancy">
+      <input type="checkbox" />
+    </span>
+    ```
+
+- ❌ Bad because it uses `div` instead of `span`
+
+    `FancyCheckbox.svelte`
+
+    ```ts
+    <div class="make-it-fancy">
+      <input type="checkbox" />
+    </div>
+    ```
+
+Rationale:
+
+- For example, let's build on the "Bad" example above and write the following Svelte code:
+
+    ```svelte
+    <label>
+      <FancyCheckbox />
+      Foo
+    </label>
+    ```
+
+    That Svelte code will render:
+
+    ```html
+    <label>
+      <div class="make-it-fancy">
+        <input type="checkbox" />
+      </div>
+      Foo
+    </label>
+    ```
+
+    That markup has invalid DOM nesting because a `label` element can only contain phrasing content -- but a `div` is _not_ phrasing content.
+
+Tips:
+
+- You can make a `span` _act_ like a `div` by setting `display: block` if needed.
+
+Notes:
+
+- Not all of our components adhere to this guideline yet.
+
+## CSS
+
+### CSS units
+
+- Don't use `px` — use `rem` or `em` instead.
+
+    Exceptional cases where `px` is okay:
+
+    - when setting the root `font-size`
+
+Note: some of our older code still does not conform to this standard.
+
+### Component spacing and layout
+
+Components should not set any space around their outer-most visual edges — instead the consuming component should be responsible for layout and spacing.
+
+- **margin**: The component's root element should not set any margin.
+
+- **padding**: If the component's root element has border, it's fine to set padding because the border will serve as the outer-most visual edge. But if there's no border, then there should be no padding.
+
+## TypeScript
+
+### `type` vs `interface`
+
+- Prefer `interface` when possible.
+- Use `type` when necessary.
+
+### `null` vs `undefined`
 
 Prefer using `undefined` over `null` where possible.
 
@@ -133,7 +220,15 @@ Additional context:
 
 - [discussion](https://github.com/centerofci/mathesar/discussions/825)
 
-## Minimize Svelte store instances
+### API type definitions
+
+TypeScript types (including interfaces) which describe API requests and responses (and properties therein) should be separated from other front end code and placed in the `mathesar_ui/src/api` directory. This structure serves to communicate that, unlike other TypeScript types, the front end does not have control over the API types.
+
+[Discussion](https://github.com/centerofci/mathesar/discussions/875)
+
+## Svelte
+
+### Minimize Svelte store instances
 
 - ✅ Good because only one `cost` store is created.
 
@@ -173,69 +268,9 @@ Additional context:
 
 - [Discussion](https://github.com/centerofci/mathesar/pull/776#issuecomment-963831424)
 
-## Build components for valid DOM nesting
-
-When working inside a component that _might_ be placed where [phrasing content](https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Content_categories#phrasing_content) is required, be sure to only use phrasing content elements (like `span`) instead of _not_-phrasing content elements (like `div`).
-
--  ✅ Good
-
-    `FancyCheckbox.svelte`
-
-    ```ts
-    <span class="make-it-fancy">
-      <input type="checkbox" />
-    </span>
-    ```
-
-- ❌ Bad because it uses `div` instead of `span`
-
-    `FancyCheckbox.svelte`
 
-    ```ts
-    <div class="make-it-fancy">
-      <input type="checkbox" />
-    </div>
-    ```
-
-Rationale:
-
-- For example, let's build on the "Bad" example above and write the following Svelte code:
-
-    ```svelte
-    <label>
-      <FancyCheckbox />
-      Foo
-    </label>
-    ```
-
-    That Svelte code will render:
-
-    ```html
-    <label>
-      <div class="make-it-fancy">
-        <input type="checkbox" />
-      </div>
-      Foo
-    </label>
-    ```
-
-    That markup has invalid DOM nesting because a `label` element can only contain phrasing content -- but a `div` is _not_ phrasing content.
-
-Tips:
-
-- You can make a `span` _act_ like a `div` by setting `display: block` if needed.
-
-Notes:
-
-- Not all of our components adhere to this guideline yet.
-
-
-## `type` vs `interface`
-
-- Prefer `interface` when possible.
-- Use `type` when necessary.
 
-## Usage of `{...$$restProps}`
+### Usage of `{...$$restProps}`
 
 We use `{...$$restProps}` occasionally in our code despite some drawbacks.