fix: Preserve block tags to preserve reconstruction/execution order

src/main/java/com/hubspot/jinjava/interpret/JinjavaInterpreter.java

@@ -427,6 +427,7 @@ private String render(Node root, boolean processExtendRoots, long renderLimit) {
       output.addNode(pathSetter);
       Optional<String> basePath = context.getCurrentPathStack().peek();
       StringBuilder ignoredOutput = new StringBuilder();
+      boolean preserveBlocks = false;
       // render all extend parents, keeping the last as the root output
       if (processExtendRoots) {
         Set<String> extendPaths = new HashSet<>();
@@ -495,10 +496,23 @@ private String render(Node root, boolean processExtendRoots, long renderLimit) {
             basePath = Optional.of(currentPath);
           }
         }
+        preserveBlocks = (context.getDeferredTokens().size() > numDeferredTokensBefore);
       }
 
       int numDeferredTokensBefore = context.getDeferredTokens().size();
       resolveBlockStubs(output);
+      if (preserveBlocks) {
+        for (BlockPlaceholderOutputNode blockPlaceholder : output.getBlocks()) {
+          blockPlaceholder.resolve(
+            EagerReconstructionUtils.wrapInTag(
+              blockPlaceholder.getValue(),
+              "block %s".formatted(blockPlaceholder.getBlockName()),
+              this,
+              false
+            )
+          );
+        }
+      }
       if (context.getDeferredTokens().size() > numDeferredTokensBefore) {
         pathSetter.setValue(
           EagerReconstructionUtils.buildBlockOrInlineSetTag(

src/test/java/com/hubspot/jinjava/EagerTest.java

@@ -1753,4 +1753,65 @@ public void itHandlesDeferredValueInRenderFilter() {
       "handles-deferred-value-in-render-filter/test"
     );
   }
+
+  @Test
+  public void itHandlesDeferredUsedInMultipleBlockLevels() {
+    expectedTemplateInterpreter.assertExpectedOutputNonIdempotent(
+      "handles-deferred-used-in-multiple-block-levels/test"
+    );
+  }
+
+  @Test
+  public void itHandlesDeferredUsedInMultipleBlockLevelsSecondPass() {
+    localContext.put("deferred", "resolved");
+    expectedTemplateInterpreter.assertExpectedOutput(
+      "handles-deferred-used-in-multiple-block-levels/test.expected"
+    );
+    expectedTemplateInterpreter.assertExpectedNonEagerOutput(
+      "handles-deferred-used-in-multiple-block-levels/test.expected"
+    );
+  }
+
+  @Test
+  public void itDoesNotDeferBlockWhenOnlyMiddleDefers() {
+    expectedTemplateInterpreter.assertExpectedOutputNonIdempotent(
+      "does-not-defer-block-when-only-middle-defers/test"
+    );
+  }
+
+  @Test
+  public void itDoesNotDeferBlockWhenOnlyMiddleDefersSecondPass() {
+    localContext.put("deferred", "resolved");
+    expectedTemplateInterpreter.assertExpectedOutput(
+      "does-not-defer-block-when-only-middle-defers/test.expected"
+    );
+    expectedTemplateInterpreter.assertExpectedNonEagerOutput(
+      "does-not-defer-block-when-only-middle-defers/test.expected"
+    );
+  }
+
+  @Test
+  public void itPreservesBlocksForReconstructionOrder() {
+    expectedTemplateInterpreter.assertExpectedOutputNonIdempotent(
+      "preserves-blocks-for-reconstruction-order/test"
+    );
+  }
+
+  @Test
+  public void itPreservesBlocksForReconstructionOrderSecondPhase() {
+    localContext.put("deferred", "resolved");
+    String twoPhaseOutput = expectedTemplateInterpreter.assertExpectedOutput(
+      "preserves-blocks-for-reconstruction-order/test.expected"
+    );
+    expectedTemplateInterpreter.assertExpectedNonEagerOutput(
+      "preserves-blocks-for-reconstruction-order/test.expected"
+    );
+    // Sanity check
+    assertThat(twoPhaseOutput)
+      .isEqualToIgnoringWhitespace(
+        expectedTemplateInterpreter.renderTemplate(
+          "preserves-blocks-for-reconstruction-order/test"
+        )
+      );
+  }
 }

src/test/java/com/hubspot/jinjava/ExpectedTemplateInterpreter.java

@@ -49,8 +49,7 @@ private ExpectedTemplateInterpreter(
   }
 
   public String assertExpectedOutput(String name) {
-    String template = getFixtureTemplate(name);
-    String output = JinjavaInterpreter.getCurrent().render(template);
+    String output = renderTemplate(name);
     assertThat(JinjavaInterpreter.getCurrent().getContext().getDeferredNodes())
       .as("Ensure no deferred nodes were created")
       .isEmpty();
@@ -60,9 +59,13 @@ public String assertExpectedOutput(String name) {
     return output;
   }
 
-  public String assertExpectedOutputNonIdempotent(String name) {
+  public String renderTemplate(String name) {
     String template = getFixtureTemplate(name);
-    String output = JinjavaInterpreter.getCurrent().render(template);
+    return JinjavaInterpreter.getCurrent().render(template);
+  }
+
+  public String assertExpectedOutputNonIdempotent(String name) {
+    String output = renderTemplate(name);
     assertThat(JinjavaInterpreter.getCurrent().getContext().getDeferredNodes())
       .as("Ensure no deferred nodes were created")
       .isEmpty();

src/test/resources/eager/does-not-defer-block-when-only-middle-defers/base.jinja

@@ -0,0 +1,12 @@
+{% set tracker_base = '1_base' %}
+
+
+-----Pre-First-----
+{% block first -%}
+{%- endblock %}
+-----Post-First-----
+-----Pre-Second-----
+{% block second -%}
+{%- endblock %}
+-----Post-Second-----
+We aren't deferring tracker base.{# This message WILL show up in final output #}

src/test/resources/eager/does-not-defer-block-when-only-middle-defers/middle.jinja

@@ -0,0 +1,13 @@
+{% extends '../../eager/does-not-defer-block-when-only-middle-defers/base.jinja' %}
+{% set tracker_middle = '2_middle' %}
+{% block first %}
+I WON'T SHOW UP
+{% endblock %}
+
+{% block second %}
+tracker_base is '1_base': {{ tracker_base }}? {{ tracker_base == '1_base' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+{% endblock %}
+Deferring tracker middle.{# This message will not show up in final output #}
+{% set tracker_middle = deferred %}

src/test/resources/eager/does-not-defer-block-when-only-middle-defers/test.expected.expected.jinja

@@ -0,0 +1,15 @@
+-----Pre-First-----
+
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': resolved? true
+tracker_test is 'resolved': resolved? true
+
+-----Post-First-----
+-----Pre-Second-----
+
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': resolved? true
+tracker_test is 'resolved': resolved? true
+
+-----Post-Second-----
+We aren't deferring tracker base.

src/test/resources/eager/does-not-defer-block-when-only-middle-defers/test.expected.jinja

@@ -0,0 +1,36 @@
+{# Start Label:  ignored_output_from_extends #}{% do %}
+
+
+
+Deferring tracker test.
+{% set tracker_test = deferred %}
+
+
+
+
+
+Deferring tracker middle.
+{% set tracker_middle = deferred %}
+{% enddo %}\
+{# End Label:  ignored_output_from_extends #}{% set current_path = 'eager/does-not-defer-block-when-only-middle-defers/base.jinja' %}
+
+
+-----Pre-First-----
+{% set __temp_meta_current_path_1008935144__,current_path = current_path,'eager/does-not-defer-block-when-only-middle-defers/test.jinja' %}
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': {{ tracker_middle }}\
+? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}\
+? {{ tracker_test == 'resolved' }}
+{% set current_path,__temp_meta_current_path_1008935144__ = __temp_meta_current_path_1008935144__,null %}
+-----Post-First-----
+-----Pre-Second-----
+{% set __temp_meta_current_path_245328778__,current_path = current_path,'eager/does-not-defer-block-when-only-middle-defers/middle.jinja' %}
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': {{ tracker_middle }}\
+? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}\
+? {{ tracker_test == 'resolved' }}
+{% set current_path,__temp_meta_current_path_245328778__ = __temp_meta_current_path_245328778__,null %}
+-----Post-Second-----
+We aren't deferring tracker base.

src/test/resources/eager/does-not-defer-block-when-only-middle-defers/test.jinja

@@ -0,0 +1,10 @@
+{% extends '../../eager/does-not-defer-block-when-only-middle-defers/middle.jinja' %}
+
+{% set tracker_test = '3_test' %}
+{% block first %}
+tracker_base is '1_base': {{ tracker_base }}? {{ tracker_base == '1_base' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+{% endblock %}
+Deferring tracker test.{# This message will not show up in final output #}
+{% set tracker_test = deferred %}

src/test/resources/eager/handles-deferred-used-in-multiple-block-levels/base.jinja

@@ -0,0 +1,27 @@
+{% set tracker_base = '1_base' %}
+
+tracker_base is '1_base': {{ tracker_base }}? {{ tracker_base == '1_base' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+-----Pre-First-----
+{% block first -%}
+tracker_base is 'resolved': {{ tracker_base }}? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+{%- endblock %}
+-----Post-First-----
+tracker_base is '1_base': {{ tracker_base }}? {{ tracker_base == '1_base' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+-----Pre-Second-----
+{% block second -%}
+tracker_base is 'resolved': {{ tracker_base }}? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+{%- endblock %}
+-----Post-Second-----
+Deferring tracker base.{# This message WILL show up in final output #}
+{% set tracker_base = deferred %}
+tracker_base is 'resolved': {{ tracker_base }}? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}

src/test/resources/eager/handles-deferred-used-in-multiple-block-levels/middle.jinja

@@ -0,0 +1,13 @@
+{% extends '../../eager/handles-deferred-used-in-multiple-block-levels/base.jinja' %}
+{% set tracker_middle = '2_middle' %}
+{% block first %}
+I WON'T SHOW UP
+{% endblock %}
+
+{% block second %}
+tracker_base is 'resolved': {{ tracker_base }}? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+{% endblock %}
+Deferring tracker middle.{# This message will not show up in final output #}
+{% set tracker_middle = deferred %}

src/test/resources/eager/handles-deferred-used-in-multiple-block-levels/test.expected.expected.jinja

@@ -0,0 +1,25 @@
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': resolved? true
+tracker_test is 'resolved': resolved? true
+-----Pre-First-----
+
+tracker_base is 'resolved': resolved? true
+tracker_middle is 'resolved': resolved? true
+tracker_test is 'resolved': resolved? true
+
+-----Post-First-----
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': resolved? true
+tracker_test is 'resolved': resolved? true
+-----Pre-Second-----
+
+tracker_base is 'resolved': resolved? true
+tracker_middle is 'resolved': resolved? true
+tracker_test is 'resolved': resolved? true
+
+-----Post-Second-----
+Deferring tracker base.
+
+tracker_base is 'resolved': resolved? true
+tracker_middle is 'resolved': resolved? true
+tracker_test is 'resolved': resolved? true

src/test/resources/eager/handles-deferred-used-in-multiple-block-levels/test.expected.jinja

@@ -0,0 +1,58 @@
+{# Start Label:  ignored_output_from_extends #}{% do %}
+
+
+
+Deferring tracker test.
+{% set tracker_test = deferred %}
+
+
+
+
+
+Deferring tracker middle.
+{% set tracker_middle = deferred %}
+{% enddo %}\
+{# End Label:  ignored_output_from_extends #}{% set current_path = 'eager/handles-deferred-used-in-multiple-block-levels/base.jinja' %}
+
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': {{ tracker_middle }}\
+? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}\
+? {{ tracker_test == 'resolved' }}
+-----Pre-First-----
+{% block first %}\
+{% set __temp_meta_current_path_1057627035__,current_path = current_path,'eager/handles-deferred-used-in-multiple-block-levels/test.jinja' %}
+tracker_base is 'resolved': {{ tracker_base }}\
+? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}\
+? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}\
+? {{ tracker_test == 'resolved' }}
+{% set current_path,__temp_meta_current_path_1057627035__ = __temp_meta_current_path_1057627035__,null %}\
+{% endblock first %}
+-----Post-First-----
+tracker_base is '1_base': 1_base? true
+tracker_middle is 'resolved': {{ tracker_middle }}\
+? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}\
+? {{ tracker_test == 'resolved' }}
+-----Pre-Second-----
+{% block second %}\
+{% set __temp_meta_current_path_697061783__,current_path = current_path,'eager/handles-deferred-used-in-multiple-block-levels/middle.jinja' %}
+tracker_base is 'resolved': {{ tracker_base }}\
+? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}\
+? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}\
+? {{ tracker_test == 'resolved' }}
+{% set current_path,__temp_meta_current_path_697061783__ = __temp_meta_current_path_697061783__,null %}\
+{% endblock second %}
+-----Post-Second-----
+Deferring tracker base.
+{% set tracker_base = deferred %}
+tracker_base is 'resolved': {{ tracker_base }}\
+? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}\
+? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}\
+? {{ tracker_test == 'resolved' }}

src/test/resources/eager/handles-deferred-used-in-multiple-block-levels/test.jinja

@@ -0,0 +1,10 @@
+{% extends '../../eager/handles-deferred-used-in-multiple-block-levels/middle.jinja' %}
+
+{% set tracker_test = '3_test' %}
+{% block first %}
+tracker_base is 'resolved': {{ tracker_base }}? {{ tracker_base == 'resolved' }}
+tracker_middle is 'resolved': {{ tracker_middle }}? {{ tracker_middle == 'resolved' }}
+tracker_test is 'resolved': {{ tracker_test }}? {{ tracker_test == 'resolved' }}
+{% endblock %}
+Deferring tracker test.{# This message will not show up in final output #}
+{% set tracker_test = deferred %}

src/test/resources/eager/preserves-blocks-for-reconstruction-order/base.jinja

@@ -0,0 +1,13 @@
+{% if deferred %}
+{% set deferred_list = [] %}
+{% endif %}
+{% do deferred_list.append('Before block') %}
+Deferred list after block is: {{ deferred_list }}
+Deferred list after block should be: ['Before block']
+-----Pre-First-----
+{% block first -%}
+{%- endblock %}
+-----Post-First-----
+{% do deferred_list.append('After block') %}
+Deferred list after block is: {{ deferred_list }}
+Deferred list after block should be: ['Before block', 'After block']

src/test/resources/eager/preserves-blocks-for-reconstruction-order/test.expected.expected.jinja

@@ -0,0 +1,12 @@
+Deferred list after block is: ['Before block']
+Deferred list after block should be: ['Before block']
+-----Pre-First-----
+
+
+Deferred list inside of block is: ['Before block', 'After block', 'In child block']
+Deferred list inside of block should be: ['Before block', 'After block', 'In child block']
+
+-----Post-First-----
+
+Deferred list after block is: ['Before block', 'After block']
+Deferred list after block should be: ['Before block', 'After block']