[latex3-commits] [git/LaTeX3-latex3-latex2e] template: Include \IfInstanceExist(TF) in lttemplate (39905349)

[Joseph Wright]

Repository : https://github.com/latex3/latex2e
On branch  : template
Link       : https://github.com/latex3/latex2e/commit/39905349dc754fa9b0279fd0d81cd4daf1d2b497

>---------------------------------------------------------------

commit 39905349dc754fa9b0279fd0d81cd4daf1d2b497
Author: Joseph Wright <joseph.wright at morningstar2.co.uk>
Date:   Sun Jun 5 12:39:16 2022 +0100

    Include \IfInstanceExist(TF) in lttemplate
    
    This is used in a number of packages:
    suggests it should be stable.


>---------------------------------------------------------------

39905349dc754fa9b0279fd0d81cd4daf1d2b497
 base/doc/usrguide3.tex                      |  8 ++++++++
 base/lttemplate.dtx                         | 25 +++++++++++++++++++++++++
 base/testfiles-lttemplate/lttemplate003.lvt | 26 ++++++++++++++++++++++++++
 base/testfiles-lttemplate/lttemplate003.tlg | 12 ++++++++++--
 4 files changed, 69 insertions(+), 2 deletions(-)

diff --git a/base/doc/usrguide3.tex b/base/doc/usrguide3.tex
index 399539c1..943263d3 100644
--- a/base/doc/usrguide3.tex
+++ b/base/doc/usrguide3.tex
@@ -1444,6 +1444,14 @@ read:
 Of course, the key names here are entirely imaginary, but illustrate
 the general idea of fixing some settings.
 
+\begin{decl}
+  |\IfInstanceExistT| \arg{obj.~type} \arg{instance} \arg{true code} \\
+  |\IfInstanceExistF| \arg{obj.~type} \arg{instance} \arg{false code} \\
+  |\IfInstanceExistTF| \arg{obj.~type} \arg{instance} \arg{true code} \arg{false code}
+\end{decl}
+Tests if the named \meta{instance} of a \meta{object type} exists, and
+then inserts the appropriate code into the input stream.
+
 \subsection{Document interface}
 
 After the instances have been chosen, document commands must be
diff --git a/base/lttemplate.dtx b/base/lttemplate.dtx
index a006d162..d55e173a 100644
--- a/base/lttemplate.dtx
+++ b/base/lttemplate.dtx
@@ -358,6 +358,19 @@
 %    \end{macrocode}
 % \end{macro}
 %
+% \begin{macro}[TF]{\@@_if_instance_exist:nn}
+%   Testing for an instance.
+%    \begin{macrocode}
+\prg_new_conditional:Npnn \@@_if_instance_exist:nn #1#2
+  { T, F, TF }
+  {
+    \cs_if_exist:cTF { \c_@@_instances_root_tl #1 / #2 }
+      { \prg_return_true: }
+      { \prg_return_false: }
+ }
+%    \end{macrocode}
+% \end{macro}
+%
 % \begin{macro}{\@@_if_use_template:nTF}
 %   Tests for the first token in a string being \cs{UseTemplate}.
 %    \begin{macrocode}
@@ -1954,6 +1967,18 @@
 % \end{macro}
 % \end{macro}
 %
+% \begin{macro}[TF]{\IfInstanceExist}
+%   Simple copies.
+%    \begin{macrocode}
+\cs_new:Npn \IfInstanceExistTF #1#2
+  { \@@_if_instance_exist:nnTF {#1} {#2} }
+\cs_new:Npn \IfInstanceExistT #1#2
+  { \@@_if_instance_exist:nnT {#1} {#2} }
+\cs_new:Npn \IfInstanceExistF #1#2
+  { \@@_if_instance_exist:nnF {#1} {#2} }
+%    \end{macrocode}
+% \end{macro}
+%
 % \begin{macro}{\KeyValue}
 %   Simply dump the argument when executed: this should not happen.
 %    \begin{macrocode}
diff --git a/base/testfiles-lttemplate/lttemplate003.lvt b/base/testfiles-lttemplate/lttemplate003.lvt
index 951bf353..8811d142 100644
--- a/base/testfiles-lttemplate/lttemplate003.lvt
+++ b/base/testfiles-lttemplate/lttemplate003.lvt
@@ -329,6 +329,32 @@
   \ShowTemplateVariables {test} {tname3}
 }
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+% 17
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+\TEST{Testing~instances:~existance~check}{
+
+   \IfInstanceExistTF {test} {nono}                      % instance unknwon, ok
+        {\typeout{Yes}} {\typeout{No}}
+
+   \IfInstanceExistTF {missingobjecttype} {nono}         % objecttype unknown, ok
+        {\typeout{Yes}} {\typeout{No}}
+
+   \group_begin:
+
+     \DeclareInstance {test} {myinstance} {tname2} {}
+
+     \IfInstanceExistTF {test} {myinstance}              % test inside group, ok
+	  {\typeout{Yes}} {\typeout{No}}
+
+   \group_end:
+
+     \IfInstanceExistTF {test} {myinstance}              % test outside group
+	  {\typeout{Yes}} {\typeout{No}}                 % no longer defined, ok
+
+}
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % 18
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
diff --git a/base/testfiles-lttemplate/lttemplate003.tlg b/base/testfiles-lttemplate/lttemplate003.tlg
index f703f8a6..bf7cb034 100644
--- a/base/testfiles-lttemplate/lttemplate003.tlg
+++ b/base/testfiles-lttemplate/lttemplate003.tlg
@@ -318,7 +318,16 @@ The template 'tname3' of object type 'test' has variable mapping:
 l. ...}
 ============================================================
 ============================================================
-TEST 17: Testing instances: declare instance
+TEST 17: Testing instances: existance check
+============================================================
+No
+No
+Defining \template values > test/myinstance on line ...
+Yes
+No
+============================================================
+============================================================
+TEST 18: Testing instances: declare instance
 ============================================================
 ! Package template Error: The template 'never-defined' of type 'test' is
 (template)                unknown or has no implementation.
@@ -327,7 +336,6 @@ For immediate help type H <return>.
 l. ...}
 There is no code available for the template name given.
 This should be given using \DeclareTemplateCode .
-Defining \template values > test/myinstance on line ...
 Defining \template values > test/myinstance2 on line ...
 hello
 (X-99)