[IMP] parser: add support for custom directives

This commit adds the support for custom directives. To use the
custom directive, an Object of functions needs to be configured on
the owl APP:
```js
 new App(..., {
    customDirectives: {
     test_directive: function (el, value) {
            el.setAttribute("t-on-click", value);
            return el;
       }
   }
  });
```
The functions will be called when a custom directive with the name of the
function is found. The original element will be replaced with the one
returned by the function.
This :
```xml
<div t-custom-test_directive="click" />
```
will be replace by :
```xml
<div t-on-click="value"/>
```

issue : https://github.com/odoo/owl/issues/1650

src/common/types.ts

@@ -0,0 +1,4 @@
+export type customDirectives = Record<
+  string,
+  (node: Element, value: string, modifier?: string) => void
+>;

src/compiler/index.ts

@@ -1,3 +1,4 @@
+import type { customDirectives } from "../common/types";
 import type { TemplateSet } from "../runtime/template_set";
 import type { BDom } from "../runtime/blockdom";
 import { CodeGenerator, Config } from "./code_generator";
@@ -10,13 +11,14 @@ export type TemplateFunction = (app: TemplateSet, bdom: any, helpers: any) => Te
 
 interface CompileOptions extends Config {
   name?: string;
+  customDirectives?: customDirectives;
 }
 export function compile(
   template: string | Element,
   options: CompileOptions = {}
 ): TemplateFunction {
   // parsing
-  const ast = parse(template);
+  const ast = parse(template, options.customDirectives);
 
   // some work
   const hasSafeContext =

src/compiler/parser.ts

@@ -1,4 +1,5 @@
 import { OwlError } from "../common/owl_error";
+import type { customDirectives } from "../common/types";
 import { parseXML } from "../common/utils";
 
 // -----------------------------------------------------------------------------
@@ -198,23 +199,26 @@ export type AST =
 // -----------------------------------------------------------------------------
 const cache: WeakMap<Element, AST> = new WeakMap();
 
-export function parse(xml: string | Element): AST {
+export function parse(xml: string | Element, customDir?: customDirectives): AST {
+  const ctx = {
+    inPreTag: false,
+    customDirectives: customDir,
+  };
   if (typeof xml === "string") {
     const elem = parseXML(`<t>${xml}</t>`).firstChild as Element;
-    return _parse(elem);
+    return _parse(elem, ctx);
   }
   let ast = cache.get(xml);
   if (!ast) {
     // we clone here the xml to prevent modifying it in place
-    ast = _parse(xml.cloneNode(true) as Element);
+    ast = _parse(xml.cloneNode(true) as Element, ctx);
     cache.set(xml, ast);
   }
   return ast;
 }
 
-function _parse(xml: Element): AST {
+function _parse(xml: Element, ctx: ParsingContext): AST {
   normalizeXML(xml);
-  const ctx = { inPreTag: false };
   return parseNode(xml, ctx) || { type: ASTType.Text, value: "" };
 }
 
@@ -222,6 +226,7 @@ interface ParsingContext {
   tModelInfo?: TModelInfo | null;
   nameSpace?: string;
   inPreTag: boolean;
+  customDirectives?: customDirectives;
 }
 
 function parseNode(node: Node, ctx: ParsingContext): AST | null {
@@ -229,6 +234,7 @@ function parseNode(node: Node, ctx: ParsingContext): AST | null {
     return parseTextCommentNode(node, ctx);
   }
   return (
+    parseTCustom(node, ctx) ||
     parseTDebugLog(node, ctx) ||
     parseTForEach(node, ctx) ||
     parseTIf(node, ctx) ||
@@ -277,6 +283,37 @@ function parseTextCommentNode(node: Node, ctx: ParsingContext): AST | null {
   return null;
 }
 
+function parseTCustom(node: Element, ctx: ParsingContext): AST | null {
+  if (!ctx.customDirectives) {
+    return null;
+  }
+  const nodeAttrsNames = node.getAttributeNames();
+  for (let attr of nodeAttrsNames) {
+    if (attr === "t-custom" || attr === "t-custom-") {
+      throw new OwlError("Missing custom directive name with t-custom directive");
+    }
+    if (attr.startsWith("t-custom-")) {
+      const directiveName = attr.split(".")[0].slice(9);
+      const customDirective = ctx.customDirectives[directiveName];
+      if (!customDirective) {
+        throw new OwlError(`Custom directive "${directiveName}" is not defined`);
+      }
+      const value = node.getAttribute(attr)!;
+      const modifier = attr.split(".").length > 1 ? attr.split(".")[1] : undefined;
+      node.removeAttribute(attr);
+      try {
+        customDirective(node, value, modifier);
+      } catch (error) {
+        throw new OwlError(
+          `Custom directive "${directiveName}" throw the following error: ${error}`
+        );
+      }
+      return parseNode(node, ctx);
+    }
+  }
+  return null;
+}
+
 // -----------------------------------------------------------------------------
 // debugging
 // -----------------------------------------------------------------------------

src/index.ts

@@ -12,5 +12,6 @@ TemplateSet.prototype._compileTemplate = function _compileTemplate(
     dev: this.dev,
     translateFn: this.translateFn,
     translatableAttributes: this.translatableAttributes,
+    customDirectives: this.customDirectives,
   });
 };

src/runtime/template_set.ts

@@ -5,6 +5,7 @@ import { Portal, portalTemplate } from "./portal";
 import { helpers } from "./template_helpers";
 import { OwlError } from "../common/owl_error";
 import { parseXML } from "../common/utils";
+import type { customDirectives } from "../common/types";
 
 const bdom = { text, createBlock, list, multi, html, toggler, comment };
 
@@ -14,6 +15,7 @@ export interface TemplateSetConfig {
   translateFn?: (s: string) => string;
   templates?: string | Document | Record<string, string>;
   getTemplate?: (s: string) => Element | Function | string | void;
+  customDirectives?: customDirectives;
 }
 
 export class TemplateSet {
@@ -27,6 +29,7 @@ export class TemplateSet {
   translateFn?: (s: string) => string;
   translatableAttributes?: string[];
   Portal = Portal;
+  customDirectives: customDirectives;
 
   constructor(config: TemplateSetConfig = {}) {
     this.dev = config.dev || false;
@@ -42,6 +45,7 @@ export class TemplateSet {
       }
     }
     this.getRawTemplate = config.getTemplate;
+    this.customDirectives = config.customDirectives || {};
   }
 
   addTemplate(name: string, template: string | Element) {