owl/src/component/directive.ts

import { QWeb } from "../qweb/index";
import { MODS_CODE } from "../qweb/extensions";

//------------------------------------------------------------------------------
// t-component
//------------------------------------------------------------------------------

const T_COMPONENT_MODS_CODE = Object.assign({}, MODS_CODE, {
  self: "if (e.target !== vn.elm) {return}"
});

QWeb.utils.defineProxy = function defineProxy(target, source) {
  for (let k in source) {
    Object.defineProperty(target, k, {
      get() {
        return source[k];
      },
      set(val) {
        source[k] = val;
      }
    });
  }
};

/**
 * The t-component directive is certainly a complicated and hard to maintain piece
 * of code.  To help you, fellow developer, if you have to maintain it, I offer
 * you this advice: Good luck...
 *
 * Since it is not 'direct' code, but rather code that generates other code, it
 * is not easy to understand.  To help you, here  is a detailed and commented
 * explanation of the code generated by the t-component directive for the following
 * situation:
 * ```xml
 *   <Child
 *      t-key="'somestring'"
 *      flag="state.flag"
 *      t-transition="fade"/>
 * ```
 *
 * ```js
 * // we assign utils on top of the function because it will be useful for
 * // each components
 * let utils = this.utils;
 *
 * // this is the virtual node representing the parent div
 * let c1 = [], p1 = { key: 1 };
 * var vn1 = h("div", p1, c1);
 *
 * // t-component directive: we start by evaluating the expression given by t-key:
 * let key5 = "somestring";
 *
 * // def3 is the promise that will contain later either the new component
 * // creation, or the props update...
 * let def3;
 *
 * // this is kind of tricky: we need here to find if the component was already
 * // created by a previous rendering.  This is done by checking the internal
 * // `cmap` (children map) of the parent component: it maps keys to component ids,
 * // and, then, if there is an id, we look into the children list to get the
 * // instance
 * let w4 =
 *   key5 in context.__owl__.cmap
 *   ? context.__owl__.children[context.__owl__.cmap[key5]]
 *   : false;
 *
 * // We keep the index of the position of the component in the closure.  We push
 * // null to reserve the slot, and will replace it later by the component vnode,
 * // when it will be ready (do not forget that preparing/rendering a component is
 * // asynchronous)
 * let _2_index = c1.length;
 * c1.push(null);
 *
 * // we evaluate here the props given to the component. It is done here to be
 * // able to easily reference it later, and also, it might be an expensive
 * // computation, so it is certainly better to do it only once
 * let props4 = { flag: context["state"].flag };
 *
 * // If we have a component, currently rendering, but not ready yet, we do not want
 * // to wait for it to be ready if we can avoid it
 * if (w4 && w4.__owl__.renderPromise && !w4.__owl__.vnode) {
 *   // we check if the props are the same.  In that case, we can simply reuse
 *   // the previous rendering and skip all useless work
 *   if (utils.shallowEqual(props4, w4.__owl__.renderProps)) {
 *     def3 = w4.__owl__.renderPromise;
 *   } else {
 *     // if the props are not the same, we destroy the component and starts anew.
 *     // this will be faster than waiting for its rendering, then updating it
 *     w4.destroy();
 *     w4 = false;
 *   }
 * }
 *
 * if (!w4) {
 *   // in this situation, we need to create a new component.  First step is
 *   // to get a reference to the class, then create an instance with
 *   // current context as parent, and the props.
 *   let W4 = context.component && context.components[componentKey4] || QWeb.component[componentKey4];

 *   if (!W4) {
 *     throw new Error("Cannot find the definition of component 'child'");
 *   }
 *   w4 = new W4(owner, props4);
 *
 *   // Whenever we rerender the parent component, we need to be sure that we
 *   // are able to find the component instance. To do that, we register it to
 *   // the parent cmap (children map).  Note that the 'template' key is
 *   // used here, since this is what identify the component from the template
 *   // perspective.
 *   context.__owl__.cmap[key5] = w4.__owl__.id;
 *
 *   // __prepare is called, to basically call willStart, then render the
 *   // component
 *   def3 = w4.__prepare();
 *
 *   def3 = def3.then(vnode => {
 *     // we create here a virtual node for the parent (NOT the component). This
 *     // means that the vdom of the parent will be stopped here, and from
 *     // the parent's perspective, it simply is a vnode with no children.
 *     // However, it shares the same dom element with the component root
 *     // vnode.
 *     let pvnode = h(vnode.sel, { key: key5 });
 *
 *     // we add hooks to the parent vnode so we can interact with the new
 *     // component at the proper time
 *     pvnode.data.hook = {
 *       insert(vn) {
 *         // the __mount method will patch the component vdom into the elm vn.elm,
 *         // then call the mounted hooks. However, suprisingly, the snabbdom
 *         // patch method actually replace the elm by a new elm, so we need
 *         // to synchronise the pvnode elm with the resulting elm
 *         let nvn = w4.__mount(vnode, vn.elm);
 *         pvnode.elm = nvn.elm;
 *         // what follows is only present if there are animations on the component
 *         utils.transitionInsert(vn, "fade");
 *       },
 *       remove() {
 *         // override with empty function to prevent from removing the node
 *         // directly. It will be removed when destroy is called anyway, which
 *         // delays the removal if there are animations.
 *       },
 *       destroy() {
 *         // if there are animations, we delay the call to destroy on the
 *         // component, if not, we call it directly.
 *         let finalize = () => {
 *           w4.destroy();
 *         };
 *         utils.transitionRemove(vn, "fade", finalize);
 *       }
 *     };
 *     // the pvnode is inserted at the correct position in the div's children
 *     c1[_2_index] = pvnode;
 *
 *     // we keep here a reference to the parent vnode (representing the
 *     // component, so we can reuse it later whenever we update the component
 *     w4.__owl__.pvnode = pvnode;
 *   });
 * } else {
 *   // this is the 'update' path of the directive.
 *   // the call to __updateProps is the actual component update
 *   // Note that we only update the props if we cannot reuse the previous
 *   // rendering work (in the case it was rendered with the same props)
 *   def3 = def3 || w4.__updateProps(props4, extra.forceUpdate, extra.patchQueue);
 *   def3 = def3.then(() => {
 *     // if component was destroyed in the meantime, we do nothing (so, this
 *     // means that the parent's element children list will have a null in
 *     // the component's position, which will cause the pvnode to be removed
 *     // when it is patched.
 *     if (w4.__owl__.isDestroyed) {
 *       return;
 *     }
 *     // like above, we register the pvnode to the children list, so it
 *     // will not be patched out of the dom.
 *     let pvnode = w4.__owl__.pvnode;
 *     c1[_2_index] = pvnode;
 *   });
 * }
 *
 * // we register the deferred here so the parent can coordinate its patch operation
 * // with all the children.
 * extra.promises.push(def3);
 * return vn1;
 * ```
 */

QWeb.addDirective({
  name: "component",
  extraNames: ["props", "keepalive", "asyncroot"],
  priority: 100,
  atNodeEncounter({ ctx, value, node, qweb }): boolean {
    ctx.addLine("//COMPONENT");
    ctx.rootContext.shouldDefineOwner = true;
    ctx.rootContext.shouldDefineQWeb = true;
    ctx.rootContext.shouldDefineParent = true;
    ctx.rootContext.shouldDefineUtils = true;
    let keepAlive = node.getAttribute("t-keepalive") ? true : false;
    let async = node.getAttribute("t-asyncroot") ? true : false;

    // t-on- events and t-transition
    const events: [string, string[], string, string][] = [];
    let transition: string = "";
    const attributes = (<Element>node).attributes;
    const props: { [key: string]: string } = {};
    for (let i = 0; i < attributes.length; i++) {
      const name = attributes[i].name;
      const value = attributes[i].textContent!;
      if (name.startsWith("t-on-")) {
        const [eventName, ...mods] = name.slice(5).split(".");
        let extraArgs;
        let handlerName = value.replace(/\(.*\)/, function(args) {
          extraArgs = args.slice(1, -1);
          return "";
        });
        events.push([eventName, mods, handlerName, extraArgs]);
      } else if (name === "t-transition") {
        transition = value;
      } else if (!name.startsWith("t-")) {
        if (name !== "class" && name !== "style") {
          // this is a prop!
          props[name] = ctx.formatExpression(value);
        }
      }
    }

    let key = node.getAttribute("t-key");
    if (key) {
      key = ctx.formatExpression(key);
    }

    // computing the props string representing the props object
    let propStr = Object.keys(props)
      .map(k => k + ":" + props[k])
      .join(",");
    let dummyID = ctx.generateID();
    let defID = ctx.generateID();
    let componentID = ctx.generateID();
    let keyID = key && ctx.generateID();
    if (key) {
      // we bind a variable to the key (could be a complex expression, so we
      // want to evaluate it only once)
      ctx.addLine(`let key${keyID} = ${key};`);
    }
    ctx.addLine(`let def${defID};`);
    let templateID = key
      ? `key${keyID}`
      : ctx.inLoop
      ? `String(-${componentID} - i)`
      : String(componentID);
    if (ctx.allowMultipleRoots) {
      // necessary to prevent collisions
      if (!key && ctx.inLoop) {
        let id = ctx.generateID();
        ctx.addLine(`let template${id} = "_slot_" + String(-${componentID} - i)`);
        templateID = `template${id}`;
      } else {
        templateID = `"_slot_${templateID}"`;
      }
    }

    let ref = node.getAttribute("t-ref");
    let refExpr = "";
    let refKey: string = "";
    if (ref) {
      refKey = `ref${ctx.generateID()}`;
      ctx.addLine(`const ${refKey} = ${ctx.interpolate(ref)};`);
      refExpr = `context.refs[${refKey}] = w${componentID};`;
    }
    let transitionsInsertCode = "";
    if (transition) {
      transitionsInsertCode = `utils.transitionInsert(vn, '${transition}');`;
    }
    let finalizeComponentCode = `w${componentID}.${keepAlive ? "unmount" : "destroy"}();`;
    if (ref && !keepAlive) {
      finalizeComponentCode += `delete context.refs[${refKey}];`;
    }
    if (transition) {
      finalizeComponentCode = `let finalize = () => {
          ${finalizeComponentCode}
        };
        utils.transitionRemove(vn, '${transition}', finalize);`;
    }

    let createHook = "";
    let classAttr = node.getAttribute("class");
    let tattClass = node.getAttribute("t-att-class");
    let styleAttr = node.getAttribute("style");
    let tattStyle = node.getAttribute("t-att-style");
    if (tattStyle) {
      const attVar = `_${ctx.generateID()}`;
      ctx.addLine(`const ${attVar} = ${ctx.formatExpression(tattStyle)};`);
      tattStyle = attVar;
    }
    let classObj = "";
    if (classAttr || tattClass || styleAttr || tattStyle || events.length) {
      if (classAttr) {
        let classDef = classAttr
          .trim()
          .split(/\s+/)
          .map(a => `'${a}':true`)
          .join(",");
        classObj = `_${ctx.generateID()}`;
        ctx.addLine(`let ${classObj} = {${classDef}};`);
      }
      if (tattClass) {
        let tattExpr = ctx.formatExpression(tattClass);
        if (tattExpr[0] !== "{" || tattExpr[tattExpr.length - 1] !== "}") {
          tattExpr = `utils.toObj(${tattExpr})`;
        }
        if (classAttr) {
          ctx.addLine(`Object.assign(${classObj}, ${tattExpr})`);
        } else {
          classObj = `_${ctx.generateID()}`;
          ctx.addLine(`let ${classObj} = ${tattExpr};`);
        }
      }
      let eventsCode = events
        .map(function([eventName, mods, handlerName, extraArgs]) {
          let params = "owner";
          if (extraArgs) {
            if (ctx.inLoop) {
              let argId = ctx.generateID();
              // we need to evaluate the arguments now, because the handler will
              // be set asynchronously later when the widget is ready, and the
              // context might be different.
              ctx.addLine(`let arg${argId} = ${ctx.formatExpression(extraArgs)};`);
              params = `owner, arg${argId}`;
            } else {
              params = `owner, ${ctx.formatExpression(extraArgs)}`;
            }
          }
          let handler;
          if (mods.length > 0) {
            handler = `function (e) {`;
            handler += mods
              .map(function(mod) {
                return T_COMPONENT_MODS_CODE[mod];
              })
              .join("");
            handler += `owner['${handlerName}'].call(${params}, e);}`;
          } else {
            handler = `owner['${handlerName}'].bind(${params})`;
          }
          return `vn.elm.addEventListener('${eventName}', ${handler});`;
        })
        .join("");
      const styleExpr = tattStyle || (styleAttr ? `'${styleAttr}'` : false);
      const styleCode = styleExpr ? `vn.elm.style = ${styleExpr};` : "";
      createHook = `vnode.data.hook = {create(_, vn){${styleCode}${eventsCode}}};`;
    }

    ctx.addLine(
      `let w${componentID} = ${templateID} in parent.__owl__.cmap ? parent.__owl__.children[parent.__owl__.cmap[${templateID}]] : false;`
    );
    if (ctx.parentNode) {
      ctx.addLine(`let _${dummyID}_index = c${ctx.parentNode}.length;`);
    }
    let shouldProxy = false;
    if (async) {
      ctx.addLine(`const patchQueue${componentID} = [];`);
      ctx.addLine(
        `c${ctx.parentNode}.push(w${componentID} && w${componentID}.__owl__.pvnode || null);`
      );
    } else {
      if (ctx.parentNode) {
        ctx.addLine(`c${ctx.parentNode}.push(null);`);
      } else {
        let id = ctx.generateID();
        ctx.rootContext.rootNode = id;
        shouldProxy = true;
        ctx.rootContext.shouldDefineResult = true;
        ctx.addLine(`let vn${id} = {};`);
        ctx.addLine(`result = vn${id};`);
      }
    }
    ctx.addLine(`let props${componentID} = {${propStr}};`);
    ctx.addIf(
      `w${componentID} && w${componentID}.__owl__.renderPromise && !w${componentID}.__owl__.vnode`
    );
    ctx.addIf(`utils.shallowEqual(props${componentID}, w${componentID}.__owl__.renderProps)`);
    ctx.addLine(`def${defID} = w${componentID}.__owl__.renderPromise;`);
    ctx.addElse();
    ctx.addLine(`w${componentID}.destroy();`);
    ctx.addLine(`w${componentID} = false;`);
    ctx.closeIf();
    ctx.closeIf();

    ctx.addIf(`!w${componentID}`);
    // new component
    ctx.addLine(`let componentKey${componentID} = ${ctx.interpolate(value)};`);
    ctx.addLine(
      `let W${componentID} = context.components && context.components[componentKey${componentID}] || QWeb.components[componentKey${componentID}];`
    );
    // maybe only do this in dev mode...
    ctx.addLine(
      `if (!W${componentID}) {throw new Error('Cannot find the definition of component "' + componentKey${componentID} + '"')}`
    );
    if (QWeb.dev) {
      ctx.addLine(`utils.validateProps(W${componentID}, props${componentID})`);
    }
    ctx.addLine(`w${componentID} = new W${componentID}(parent, props${componentID});`);
    ctx.addLine(`parent.__owl__.cmap[${templateID}] = w${componentID}.__owl__.id;`);

    // SLOTS
    const varDefs: string[] = [];
    const hasSlots = node.childNodes.length;
    if (hasSlots) {
      ctx.rootContext.shouldTrackScope = true;
      for (let v of Object.values(ctx.variables)) {
        if (v["id"]) {
          varDefs.push(v["id"]);
        }
      }

      const clone = <Element>node.cloneNode(true);
      const slotNodes = clone.querySelectorAll("[t-set]");
      const slotId = qweb.nextSlotId++;
      ctx.addLine(`w${componentID}.__owl__.slotId = ${slotId};`);
      if (slotNodes.length) {
        for (let i = 0, length = slotNodes.length; i < length; i++) {
          const slotNode = slotNodes[i];
          slotNode.parentElement!.removeChild(slotNode);
          const key = slotNode.getAttribute("t-set")!;
          slotNode.removeAttribute("t-set");
          const slotFn = qweb._compile(`slot_${key}_template`, slotNode, ctx);
          qweb.slots[`${slotId}_${key}`] = slotFn.bind(qweb);
        }
      }
      if (clone.childNodes.length) {
        const t = clone.ownerDocument!.createElement("t");
        for (let child of Object.values(clone.childNodes)) {
          t.appendChild(child);
        }
        const slotFn = qweb._compile(`slot_default_template`, t, ctx);
        qweb.slots[`${slotId}_default`] = slotFn.bind(qweb);
      }
    }

    let scopeVars = "";
    if (hasSlots) {
      scopeVars += ctx.scopeVars.length ? `Object.assign({}, scope)` : varDefs.length ? `{}` : "";
      if (varDefs.length) {
        scopeVars += `, {${varDefs.join(",")}}`;
      }
    }
    ctx.addLine(`def${defID} = w${componentID}.__prepare(${scopeVars});`);
    // hack: specify empty remove hook to prevent the node from being removed from the DOM
    let registerCode = `c${ctx.parentNode}[_${dummyID}_index]=pvnode;`;
    if (shouldProxy) {
      registerCode = `utils.defineProxy(vn${ctx.rootNode}, pvnode);`;
    }
    ctx.addLine(
      `def${defID} = def${defID}.then(vnode=>{${createHook}let pvnode=h(vnode.sel, {key: ${templateID}, hook: {insert(vn) {let nvn=w${componentID}.__mount(vnode, pvnode.elm);pvnode.elm=nvn.elm;${refExpr}${transitionsInsertCode}},remove() {},destroy(vn) {${finalizeComponentCode}}}});${registerCode}w${componentID}.__owl__.pvnode = pvnode;});`
    );

    ctx.addElse();
    // need to update component
    let patchQueueCode = async ? `patchQueue${componentID}` : "extra.patchQueue";
    if (keepAlive) {
      // if we have t-keepalive="1", the component could be unmounted, but then
      // we __updateProps is called.  This is ok, but we do not want to call
      // the willPatch/patched hooks of the component in this case, so we
      // disable the patch queue
      patchQueueCode = `w${componentID}.__owl__.isMounted ? ${patchQueueCode} : []`;
    }
    if (QWeb.dev) {
      ctx.addLine(`utils.validateProps(w${componentID}.constructor, props${componentID})`);
    }
    ctx.addLine(
      `def${defID} = def${defID} || w${componentID}.__updateProps(props${componentID}, extra.forceUpdate, ${patchQueueCode}${scopeVars &&
        ", " + scopeVars});`
    );
    let keepAliveCode = "";
    if (keepAlive) {
      keepAliveCode = `pvnode.data.hook.insert = vn => {vn.elm.parentNode.replaceChild(w${componentID}.el,vn.elm);vn.elm=w${componentID}.el;w${componentID}.__remount();};`;
    }
    ctx.addLine(
      `def${defID} = def${defID}.then(()=>{if (w${componentID}.__owl__.isDestroyed) {return};${
        tattStyle ? `w${componentID}.el.style=${tattStyle};` : ""
      }let pvnode=w${componentID}.__owl__.pvnode;${keepAliveCode}${registerCode}});`
    );
    ctx.closeIf();

    if (classObj) {
      ctx.addLine(`w${componentID}.__owl__.classObj=${classObj};`);
    }

    if (async) {
      ctx.addLine(
        `def${defID}.then(w${componentID}.__applyPatchQueue.bind(w${componentID}, patchQueue${componentID}));`
      );
    } else {
      ctx.addLine(`extra.promises.push(def${defID});`);
    }

    if (node.hasAttribute("t-if") || node.hasAttribute("t-else") || node.hasAttribute("t-elif")) {
      ctx.closeIf();
    }

    return true;
  }
});