[Nant-users] Typed properties

[Jaroslaw Kowalski]

Hi guys!   I'd like to propose the introduction of typed properties to NAnt. Currently properties are stored as strings which has many drawbacks, esp. when used within expressions. For example:   <property name="a" value="false" /> <if test="${a=false}">     ... </if>   this test fails because: 1. "a" is stored as a string 2. equality operator promotes "false" literal to string which becomes "False" (note the initial cap - this is what Convert.ToString() does) the compares both sides as strings. 3. 'false' != 'False'   My idea is to:   1. Disallow ALL implicit conversions for operators - to avoid such confusions 2. Add support for typed properties - to let properties store values of types other than strings. It would involve type checking on assignment and type-safe retrieval.   The proposed syntax would be:   <property name="a" type="bool" value="false" /> <property name="b" type="int" value="${1+1234}" />   When "type" is omitted - "string" is assumed by default for compatibility.   The following would fail because of incompatible types:   <property name="a" type="bool" value="3" /> <property name="a" type="int" value="false" /> <property name="a" type="float" value="zzz" />   Assuming we disallow all implicit conversions:   <property name="a" type="bool" value="true" /> <property name="b" type="bool" value="false" /> <property name="c" type="int" value="123" /> <property name="d" type="int" value="321" /> <property name="e" type="string" value="456" />   <echo message="${a + b}" /> ------ causes an error, today it outputs 'TrueFalse' <echo message="${'aaa' + b}" /> --- causes an error, today it outputs aaaFalse <echo message="${'aaa' + convert::to-string(b)}" /> --- outputs aaaFalse <echo message="${c + d}" /> ------ outputs 444, today it outputs 123321 <echo message="${c + e}" /> ------ fails, currently it outputs 123456 <echo message="${convert::to-string(c) + e}" /> ------ outputs 123456 <echo message="${c + convert::to-int(e)}" /> ------ outputs 579   Implicit conversion would still be applied when passing arguments to functions: Assuming   int fun(int k) { return k; }   <echo message="${fun(e) + 1}}" /> ------ outputs 457   There are probably more consequences of this idea, if you see any danger - let me know. I'm awaiting your comments. If this idea passes, I'll prepare the appropriate patch. Initial feasibility study shows that it's possible to do it without breaking compatibility.   Jarek