[ADD] web: Add extra condition branching (t-elif, t-else)

A new preprocess method is added to the template engine in order to do
preprocessing/sanitization of the templates before compilation.
This method can be overloaded in order to add new features such as
translation, ...

addons/web/static/lib/qweb/qweb-test-conditionals.xml

@@ -16,16 +16,27 @@
     </t>
     <result id="boolean-value-condition-missing"/>
 
+    <!-- TODO: activate this test when qweb.py implements t-elif
+    <t t-name="boolean-value-condition-elif">
+        <t t-if="color == 'black'">black pearl</t>
+        <t t-elif="color == 'yellow'">yellow submarine</t>
+        <t t-elif="color == 'red'">red is dead</t>
+        <t t-else="">beer</t>
+    </t>
+    <params id="boolean-value-condition-elif">{"color": "red"}</params>
+    <result id="boolean-value-condition-elif">red is dead</result>
+    -->
+
     <t t-name="boolean-value-condition-else">
         <div><span>begin</span><t t-if="condition">ok</t>
-        <t t-else="t-else">ok-else</t><span>end</span></div>
+        <t t-else="">ok-else</t><span>end</span></div>
     </t>
     <params id="boolean-value-condition-else">{"condition": true}</params>
     <result id="boolean-value-condition-else"><![CDATA[<div><span>begin</span>ok<span>end</span></div>]]></result>
 
     <t t-name="boolean-value-condition-false-else">
         <div><span>begin</span><t t-if="condition">fail</t>
-        <t t-else="t-else">fail-else</t><span>end</span></div>
+        <t t-else="">fail-else</t><span>end</span></div>
     </t>
     <params id="boolean-value-condition-false-else">{"condition": false}</params>
     <result id="boolean-value-condition-false-else"><![CDATA[<div><span>begin</span>fail-else<span>end</span></div>]]></result>

addons/web/static/lib/qweb/qweb2.js

@@ -28,7 +28,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 var QWeb2 = {
     expressions_cache: { },
     RESERVED_WORDS: 'true,false,NaN,null,undefined,debugger,console,window,in,instanceof,new,function,return,this,typeof,eval,void,Math,RegExp,Array,Object,Date'.split(','),
-    ACTIONS_PRECEDENCE: 'foreach,if,call,set,esc,raw,js,debug,log'.split(','),
+    ACTIONS_PRECEDENCE: 'foreach,if,elif,else,call,set,esc,raw,js,debug,log'.split(','),
     WORD_REPLACEMENT: {
         'and': '&&',
         'or': '||',
@@ -112,6 +112,15 @@ var QWeb2 = {
             }
             return -1;
         },
+        get_element_sibling: function(node, dom_attr) {
+            // This helper keeps support for IE8 which does not
+            // implement DOMNode.(previous|next)ElementSibling
+            var sibling = node[dom_attr];
+            while (sibling && sibling.nodeType !== 1) {
+                sibling = sibling[dom_attr];
+            }
+            return sibling;
+        },
         xml_node_to_string : function(node, childs_only) {
             if (childs_only) {
                 var childs = node.childNodes, r = [];
@@ -242,13 +251,11 @@ QWeb2.Engine = (function() {
                     self.add_template(xDoc, callback);
                 });
             }
+            template = this.preprocess(template);
             var ec = (template.documentElement && template.documentElement.childNodes) || template.childNodes || [];
             for (var i = 0; i < ec.length; i++) {
                 var node = ec[i];
                 if (node.nodeType === 1) {
-                    if (node.nodeName == 'parsererror') {
-                        return this.tools.exception(node.innerText);
-                    }
                     var name = node.getAttribute(this.prefix + '-name');
                     var extend = node.getAttribute(this.prefix + '-extend');
                     if (name && extend) {
@@ -278,6 +285,56 @@ QWeb2.Engine = (function() {
             }
             return true;
         },
+        preprocess: function(doc) {
+            /**
+             * Preprocess a template's document at load time.
+             * This method is mostly used for template sanitization but could
+             * also be overloaded for extended features such as translations, ...
+             * Throws an exception if a template is invalid.
+             *
+             * @param {Document} doc Document containg the loaded templates
+             * @return {Document} Returns the pre-processed/sanitized template
+             */
+            var self = this;
+            var childs = (doc.documentElement && doc.documentElement.childNodes) || doc.childNodes || [];
+
+            // Check for load errors
+            for (var i = 0; i < childs.length; i++) {
+                var node = childs[i];
+                if (node.nodeType === 1 && node.nodeName == 'parsererror') {
+                    return this.tools.exception(node.innerText);
+                }
+            }
+
+            // Sanitize t-elif and t-else directives
+            var tbranch = doc.querySelectorAll('[t-elif], [t-else]');
+            for (var i = 0, ilen = tbranch.length; i < ilen; i++) {
+                var node = tbranch[i];
+                var prev_elem = self.tools.get_element_sibling(node, 'previousSibling');
+                var pattr = function(name) { return prev_elem.getAttribute(name); }
+                var nattr = function(name) { return +!!node.getAttribute(name); }
+                if (prev_elem && (pattr('t-if') || pattr('t-elif'))) {
+                    if (pattr('t-foreach')) {
+                        return self.tools.exception("Error: t-if cannot stay at the same level as t-foreach when using t-elif or t-else");
+                    }
+                    if (['t-if', 't-elif', 't-else'].map(nattr).reduce(function(a, b) { return a + b; }) > 1) {
+                        return self.tools.exception("Error: only one conditional branching directive is allowed per node");
+                    }
+                    // All text nodes between branch nodes are removed
+                    var text_node;
+                    while ((text_node = node.previousSibling) !== prev_elem) {
+                        if (self.tools.trim(text_node.nodeValue)) {
+                            return self.tools.exception("Error: text is not allowed between branching directives");
+                        }
+                        text_node.remove();
+                    }
+                } else {
+                    return self.tools.exception("Error: t-elif and t-else directives must be preceded by a t-if or t-elif directive");
+                }
+            }
+
+            return doc;
+        },
         load_xml : function(s, callback) {
             var self = this;
             var async = !!callback;
@@ -704,6 +761,16 @@ QWeb2.Element = (function() {
             this.bottom("}");
             this.indent();
         },
+        compile_action_elif : function(value) {
+            this.top("else if (" + (this.format_expression(value)) + ") {");
+            this.bottom("}");
+            this.indent();
+        },
+        compile_action_else : function(value) {
+            this.top("else {");
+            this.bottom("}");
+            this.indent();
+        },
         compile_action_foreach : function(value) {
             var as = this.actions['as'] || value.replace(/[^a-zA-Z0-9]/g, '_');
             //TODO: exception if t-as not valid

doc/reference/qweb.rst

@@ -95,6 +95,16 @@ not have to be ``<t>``::
 
 will give the same results as the previous example.
 
+Extra conditional branching directives ``t-elif`` and ``t-else`` are also
+available::
+
+    <div>
+        <p t-if="user.birthday == today()">Happy bithday!</p>
+        <p t-elif="user.login == 'root'">Welcome master!</p>
+        <p t-else="">Welcome!</p>
+    </div>
+
+
 .. _reference/qweb/loops:
 
 loops