Qute - ignore parentheses when parsing a value of an expression

- this makes it possible to use the infix notation in section parameters
and default values of type-safe paramerer declarations, e.g. "{#let foo
= (val ? 1 : 2)}"

docs/src/main/asciidoc/qute-reference.adoc

@@ -576,9 +576,13 @@ It may be empty, i.e. the start tag ends with `/`: `{#myEmptySection /}`.
 Sections usually contain nested expressions and other sections.
 The end tag starts with `/` and contains the name of the section (optional): `{#if foo}Foo!{/if}` or `{#if foo}Foo!{/}`.
 
-The start tag can also define parameters: `{#if item.isActive}`.
-Parameters are separated by one or more spaces. 
-However, parameters can have optional names separated by the equals sign prefixed and suffixed with any number of spaces, e.g. `{#let id='Foo'}` and `{#let id = 'Foo'}` are equivalents where the name of the parameter is `id` and the value is `Foo`.
+A start tag can define parameters with optional names, e.g. `{#if item.isActive}` and `{#let foo=1 bar=false}`.
+Parameters are separated by one or more spaces.
+Names are separated from the values by the equals sign.
+Names and values can be prefixed and suffixed with any number of spaces, e.g. `{#let id='Foo'}` and `{#let id  = 'Foo'}` are equivalents where the name of the parameter is `id` and the value is `Foo`.
+Values can be grouped using parentheses, e.g. `{#let id=(item.id ?: 42)}` where the name is `id` and the value is `item.id ?: 42`. 
+Sections can interpret parameter values in any way, e.g. take the value as is.
+However, in most cases the parameter value is registered as an <<expressions,expression>> and evaluated before use.
 
 A section may contain several content *blocks*. 
 The "main" block is always present.
@@ -903,14 +907,15 @@ This section allows you to define named local variables:
 
 [source,html]
 ----
-{#let myParent=order.item.parent isActive=false age=10} <1>
+{#let myParent=order.item.parent isActive=false age=10 price=(order.price + 10)} <1><2>
   <h1>{myParent.name}</h1>
   Is active: {isActive}
   Age: {age}
-{/let} <2>
+{/let} <3>
 ----
-<1> The local variable is initialized with an expression that can also represent a <<literals,literal>>.
-<2> Keep in mind that the variable is not available outside the `let` section that defines it.
+<1> The local variable is initialized with an expression that can also represent a <<literals,literal>>, i.e. `isActive=false` and `age=10`.
+<2> The infix notation is only supported if parentheses are used for grouping, e.g. `price=(order.price + 10)` is equivalent to `price=order.price.plus(10)`.
+<3> Keep in mind that the variable is not available outside the `let` section that defines it.
 
 If a key of a section parameter (aka the name of the local variable) ends with a `?` then the local variable is only set if the key without the `?` suffix resolves to `null` or _"not found"_:
 
@@ -1547,7 +1552,7 @@ On the other hand, if the value is set (e.g. via `TemplateInstance.data("foo", "
 
 The type of a default value must be assignable to the type of the parameter declaration, i.e. the following parameter declaration is incorrect and results in a build failure: `{@org.acme.Foo foo=1}`.
 
-TIP: The default value is actually an <<expressions,expression>>. So the default value does not have to be a literal (such as `42` or `true`). For example, you can leverage the `@TemplateEnum` and specify an enum constant as a default value of a parameter declaration: `{@org.acme.MyEnum myEnum=MyEnum:FOO}`. However, the infix notation is not supported in default values.
+TIP: The default value is actually an <<expressions,expression>>. So the default value does not have to be a literal (such as `42` or `true`). For example, you can leverage the `@TemplateEnum` and specify an enum constant as a default value of a parameter declaration: `{@org.acme.MyEnum myEnum=MyEnum:FOO}`. However, the infix notation is not supported in default values unless the parentheses are used for grouping, e.g. `{@org.acme.Foo foo=(foo1 ?: foo2)}``.
 
 IMPORTANT: The type of a default value is not validated in <<standalone, Qute standalone>>.
 

independent-projects/qute/core/src/main/java/io/quarkus/qute/Parser.java

@@ -907,6 +907,10 @@ static ExpressionImpl parseExpression(Supplier<Integer> idGenerator, String valu
         if (value == null || value.isEmpty()) {
             return ExpressionImpl.EMPTY;
         }
+        // (foo ?: bar) -> foo ?: bar
+        if (value.charAt(0) == START_COMPOSITE_PARAM && value.charAt(value.length() - 1) == END_COMPOSITE_PARAM) {
+            value = value.substring(1, value.length() - 1);
+        }
         String namespace = null;
         int namespaceIdx = value.indexOf(NAMESPACE_SEPARATOR);
         int spaceIdx;

independent-projects/qute/core/src/main/java/io/quarkus/qute/SectionHelperFactory.java

@@ -95,6 +95,7 @@ default boolean treatUnknownSectionsAsBlocks() {
     }
 
     /**
+     * Initialize a new helper instance for a specific section node in a template.
      *
      * @param context
      * @return a new helper instance
@@ -103,6 +104,12 @@ default boolean treatUnknownSectionsAsBlocks() {
 
     /**
      * Initialize a section block.
+     * <p>
+     * All section blocks are initialized before {@link #initialize(SectionInitContext)} is called.
+     * <p>
+     * The factory is responsible to register all expression via {@link BlockInfo#addExpression(String, String)}. The expression
+     * can be then used during {@link #initialize(SectionInitContext)} via {@link SectionInitContext#getExpression(String)} and
+     * {@link SectionBlock#expressions}.
      *
      * @return a new scope if this section introduces a new scope, or the outer scope
      * @see BlockInfo#addExpression(String, String)
@@ -200,7 +207,7 @@ default public String getParameterOrDefault(String name, String defaultValue) {
          * first.
          *
          * @param parameterName
-         * @return an expression registered for the specified param name, or {@code null}
+         * @return the expression registered for the main block under the specified param name, or {@code null}
          * @see BlockInfo#addExpression(String, String)
          */
         public Expression getExpression(String parameterName);

independent-projects/qute/core/src/test/java/io/quarkus/qute/ParamDeclarationDefaultValueTest.java

@@ -2,6 +2,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
 
 import java.util.List;
 
@@ -20,6 +21,16 @@ public void testDefaultValue() {
         assertDefaultValue(engine.parse("{@java.lang.String val= 'foo and bar'}\n{val.toUpperCase}"), "FOO AND BAR");
     }
 
+    @Test
+    public void testDefaultValueWithComposite() {
+        Engine engine = Engine.builder().addDefaults().addValueResolver(new ReflectionValueResolver()).build();
+        Template template = engine.parse("{@java.lang.String val=(foo or bar)}{val}");
+        assertEquals("barbar", template.data("bar", "barbar").render());
+        Expression fooExpr = template.getExpressions().stream().filter(e -> !e.isLiteral()).findFirst().orElse(null);
+        assertNotNull(fooExpr);
+        assertNull(fooExpr.collectTypeInfo());
+    }
+
     @Test
     public void testMultipleDefaultValues() {
         Engine engine = Engine.builder().addDefaults().addValueResolver(new ReflectionValueResolver()).build();

independent-projects/qute/core/src/test/java/io/quarkus/qute/SetSectionTest.java

@@ -62,4 +62,16 @@ public void testParameterOrigin() {
         }
     }
 
+    @Test
+    public void testCompositeParams() {
+        Engine engine = Engine.builder().addDefaults().addValueResolver(new ReflectionValueResolver()).build();
+        assertEquals("1x2x::false",
+                engine.parse(
+                        "{#let foo=(baz + 1) bar=(name ? true : false)}"
+                                + "{#for i in foo}{i_count}x{/for}::{bar}"
+                                + "{/let}")
+                        .data("baz", 1)
+                        .render());
+    }
+
 }