it was difficult to change just a value of a CMakeToolchain block

conan/tools/cmake/toolchain.py

@@ -51,9 +51,20 @@ class Block(object):
     def __init__(self, conanfile, toolchain):
         self._conanfile = conanfile
         self._toolchain = toolchain
+        self._context_values = None
 
-    def get_block(self):
-        context = self.context()
+    @property
+    def values(self):
+        if self._context_values is None:
+            self._context_values = self.context()
+        return self._context_values
+
+    @values.setter
+    def values(self, context_values):
+        self._context_values = context_values
+
+    def get_rendered_content(self):
+        context = self.values
         if context is None:
             return
         return Template(self.template, trim_blocks=True, lstrip_blocks=True).render(**context)
@@ -544,9 +555,9 @@ def __getitem__(self, name):
     def process_blocks(self):
         result = []
         for b in self._blocks.values():
-            block = b.get_block()
-            if block:
-                result.append(block)
+            content = b.get_rendered_content()
+            if content:
+                result.append(content)
         return result
 
 

conans/test/unittests/tools/cmake/test_cmaketoolchain.py

@@ -69,6 +69,21 @@ def context(self):
     assert 'set(CMAKE_BUILD_TYPE "SuperRelease"' in content
 
 
+def test_context_update(conanfile):
+    toolchain = CMakeToolchain(conanfile)
+    build_type = toolchain.blocks["generic_system"].values["build_type"]
+    toolchain.blocks["generic_system"].values["build_type"] = "Super" + build_type
+    content = toolchain.content
+    assert 'set(CMAKE_BUILD_TYPE "SuperRelease"' in content
+
+
+def test_context_replace(conanfile):
+    toolchain = CMakeToolchain(conanfile)
+    toolchain.blocks["generic_system"].values = {"build_type": "SuperRelease"}
+    content = toolchain.content
+    assert 'set(CMAKE_BUILD_TYPE "SuperRelease"' in content
+
+
 def test_replace_block(conanfile):
     toolchain = CMakeToolchain(conanfile)