[FIX] compiler: properly handle readonly attribute/readOnly property

Before this commit, Owl template compiler would handle readonly
attribute as readonly properties. But this is incorrect, since the
property is actually named readOnly.

With this commit, we make sure that readonly AND readOnly are both
interpreted as the `readOnly` property. This is due to the fact that
QWeb does not discriminate between attribute and properties, so we have
to infer which is which.

closes #1362

src/compiler/code_generator.ts

@@ -65,12 +65,13 @@ function isProp(tag: string, key: string): boolean {
         key === "indeterminate" ||
         key === "value" ||
         key === "readonly" ||
+        key === "readOnly" ||
         key === "disabled"
       );
     case "option":
       return key === "selected" || key === "disabled";
     case "textarea":
-      return key === "value" || key === "readonly" || key === "disabled";
+      return key === "value" || key === "readonly" || key === "readOnly" || key === "disabled";
     case "select":
       return key === "value" || key === "disabled";
     case "button":
@@ -600,6 +601,10 @@ export class CodeGenerator {
         attrName = key === "t-att" ? null : key.slice(6);
         expr = compileExpr(ast.attrs[key]);
         if (attrName && isProp(ast.tag, attrName)) {
+          if (attrName === "readonly") {
+            // the property has a different name than the attribute
+            attrName = "readOnly";
+          }
           // we force a new string or new boolean to bypass the equality check in blockdom when patching same value
           if (attrName === "value") {
             // When the expression is falsy (except 0), fall back to an empty string