[FIX] qweb: cascading t-call and t-raw="0"

Have a t-call having a t-raw="0"
that call is made to a template of the same form
i.e. itself as a t-call t-raw="0" structure

Before this commit, there was recursion crash
This was because the caller to which a t-raw="0" referred to
was incorrect. The caller here is the node which makes the t-call.
In particular, the caller was always set to last caller of the context

After this commit, there is no crash and this imbrication
of t-call and t-raw="0" is well rendered.
To sum up, we count the recursive calls to t-raw="0" and fetch
the caller in the context accordingly

closes #510

src/qweb/base_directives.ts

@@ -28,9 +28,12 @@ QWeb.utils.getFragment = function(str: string): DocumentFragment {
 QWeb.utils.htmlToVDOM = htmlToVDOM;
 
 function compileValueNode(value: any, node: Element, qweb: QWeb, ctx: CompilationContext) {
-  if (value === "0" && ctx.caller) {
-    qweb._compileNode(ctx.caller, ctx);
-    return;
+  if (value === "0") {
+    const caller = ctx.getCaller();
+    if (caller) {
+      qweb._compileNode(caller, ctx.getInliningContext());
+      return;
+    }
   }
 
   if (value.xml instanceof NodeList && !value.id) {

src/qweb/compilation_context.ts

@@ -32,6 +32,8 @@ export class CompilationContext {
   scopeVars: any[] = [];
   currentKey: string = "";
   templates: { [key: string]: boolean } = {};
+  callingLevel: number = 0;
+  inliningLevel: number = 0;
 
   constructor(name?: string) {
     this.rootContext = this;
@@ -129,6 +131,10 @@ export class CompilationContext {
   subContext(key: keyof CompilationContext, value: any): CompilationContext {
     const newContext = Object.create(this);
     newContext[key] = value;
+    if (key === 'caller') {
+      newContext.callingLevel++;
+      newContext.inliningLevel++;
+    }
     return newContext;
   }
 
@@ -166,6 +172,27 @@ export class CompilationContext {
     this.dedent();
     this.addLine("}");
   }
+  /**
+   * Recursively (inverse) fetches the `caller` of a context
+   * Useful to determine to which t-call a t-raw="0" refers
+   */
+  getCaller(targetLevel?: number): Element | null {
+    if (targetLevel === undefined) {
+      targetLevel = this.inliningLevel;
+    }
+    if (targetLevel === this.callingLevel) {
+      return this.caller || null;
+    }
+    const proto = (this as any).__proto__;
+    return proto ? proto.getCaller(targetLevel) : null;
+  }
+  /**
+   * Marks the context with the current recursive level
+   * in which we are for inlining archs (t-raw="0")
+   */
+  getInliningContext(): CompilationContext {
+    return this.subContext('inliningLevel', this.inliningLevel - 1);
+  }
 
   getValue(val: any): QWebVar | string {
     return val in this.variables ? this.getValue(this.variables[val]) : val;