[stringtemplate-interest] ST4: New feature STGroup.unloadMore() ?

[Udo Borkowski]

Hi,

currently the STGroup method unload() 

	"unloads" all templates and dictionaries but leave renderers, adaptors, and import relationships. 

Notice "import relationships" are not unloaded.

Other than renderers and adaptors the import relationship is often defined inside the group text and not by explicitly calling STGroup.importTemplates(…). This may lead to strange issues when the import list in the group text in the file is modified (especially when imports are removed/replaced) and stGroup.unload() is used to force next getInstanceOf to reload templates..

Example:

t.stg
==========
import "g1.stg"

main() ::= <<
v1-<f()>
>>
==========

g1.stg
==========
f() ::= "g1"
==========

g2.stg
==========
f() ::= "g2"
f2() ::= "f2 in g2"
==========

Calling t/main() correctly renders "g1".

Now we modify "t.stg" to
==========
import "g2.stg"

main() ::= <<
v2-<f()>;<f2()>
>>
==========

and call unload() for that group.

We now render test/main() and get "v2-g1;f2", however I would have expected "v2-g2;f2".

This is because group t now holds the groups "g1" and "g2" in its "imports". "g1" was not removed. So when looking for template "f" it is first found in "g1" and used. When looking for "f2" it finds nothing in g1, but in g2. So both g1 and g2 are used for rendering.

What about introducing a new method unloadMore() that also unloads the import relationships?

I tried adding this to STGroup:

	/**
	 * As {@link #unload()}, but also "unloads" the import relationships, i.e.
	 * already imported groups will be "re-imported".
	 */
	public synchronized void unloadMore() {
		unload();
		imports.clear();
	}
	
Here a little test to check the result the new method STGroup.unloadMore:

	@Test
	public void testUnloadMore() throws Exception {
		writeFile(tmpdir, "t.stg",
				"import \"g1.stg\"\n\nmain() ::= <<\nv1-<f()>\n>>");
		writeFile(tmpdir, "g1.stg", "f() ::= \"g1\"");
		writeFile(tmpdir, "g2.stg", "f() ::= \"g2\"\nf2() ::= \"f2\"\n");
		STGroup group = new org.stringtemplate.v4.STGroupFile(tmpdir + "/t.stg");
		ST st = group.getInstanceOf("main");
		Assert.assertEquals("v1-g1", st.render());

		// Change the imports of group t.
		writeFile(tmpdir, "t.stg",
				"import \"g2.stg\"\n\nmain() ::= <<\nv2-<f()>;<f2()>\n>>");
		group.unloadMore(); // will also unload already imported groups
		st = group.getInstanceOf("main");
		Assert.assertEquals("v2-g2;f2", st.render());
	}


Shall I add this to the sources? Got a better name than "unloadMore"?

Udo


PS.: Here the corresponding test for STGroupUnload:

	@Test
	public void testUnloadMore() throws Exception {
		writeFile(tmpdir, "t.stg",
				"import \"g1.stg\"\n\nmain() ::= <<\nv1-<f()>\n>>");
		writeFile(tmpdir, "g1.stg", "f() ::= \"g1\"");
		writeFile(tmpdir, "g2.stg", "f() ::= \"g2\"\nf2() ::= \"f2\"\n");
		STGroup group = new org.stringtemplate.v4.STGroupFile(tmpdir + "/t.stg");
		ST st = group.getInstanceOf("main");
		Assert.assertEquals("v1-g1", st.render());

		// Change the imports of group t.
		writeFile(tmpdir, "t.stg",
				"import \"g2.stg\"\n\nmain() ::= <<\nv2-<f()>;<f2()>\n>>");
		group.unloadMore(); // will also unload already imported groups
		st = group.getInstanceOf("main");
		Assert.assertEquals("v2-g2;f2", st.render());
	}



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