Map snippets to IfVersion contexts

scripts/snippets/model.py

@@ -173,3 +173,9 @@ class SnippetAttributeIssue:
     rule: SnippetAttributeRule
     span: Span
     message: str
+
+
+@dataclass(frozen=True)
+class SnippetConditionContext:
+    snippet: SnippetTag
+    condition: IfVersionCondition | None

scripts/snippets/semantics.py

@@ -1,12 +1,16 @@
 from __future__ import annotations
 
 from .model import (
+    ElseTag,
+    IfVersionCondition,
+    IfVersionTag,
     ImmutableSourceReference,
     LocalSourceReference,
     PullRequestSnippetSource,
     PullRequestSourceReference,
     SnippetAttributeIssue,
     SnippetAttributeRule,
+    SnippetConditionContext,
     SnippetSourceAttributeIssue,
     SnippetSourceAttributeRule,
     SnippetSourceAttributeValidation,
@@ -136,3 +140,35 @@ def validate_snippet_basic_attributes(
             )
         )
     return tuple(issues)
+
+
+def map_snippet_condition_contexts(
+    snippets: tuple[SnippetTag, ...],
+    conditional_tags: tuple[IfVersionTag | ElseTag, ...],
+    conditions: tuple[IfVersionCondition, ...],
+) -> tuple[SnippetConditionContext, ...]:
+    """Associate snippets with their innermost enclosing IfVersion condition."""
+
+    conditions_by_start = {
+        condition.span.start: condition for condition in conditions
+    }
+    events = sorted(
+        (*snippets, *conditional_tags), key=lambda event: event.span.start
+    )
+    stack: list[IfVersionCondition | None] = []
+    contexts: list[SnippetConditionContext] = []
+    for event in events:
+        if isinstance(event, IfVersionTag):
+            if event.closing:
+                if stack:
+                    stack.pop()
+            else:
+                stack.append(conditions_by_start.get(event.span.start))
+        elif isinstance(event, SnippetTag):
+            contexts.append(
+                SnippetConditionContext(
+                    snippet=event,
+                    condition=stack[-1] if stack else None,
+                )
+            )
+    return tuple(contexts)

tests/test_snippet_condition_context.py

@@ -0,0 +1,75 @@
+from __future__ import annotations
+
+from scripts.snippets.model import IfVersionCondition, IfVersionTag
+from scripts.snippets.references import parse_github_repository_url
+from scripts.snippets.semantics import map_snippet_condition_contexts
+from scripts.snippets.syntax import (
+    parse_if_version_tags,
+    parse_snippet_tags,
+)
+
+
+def conditions(text: str) -> tuple[IfVersionCondition, ...]:
+    result: list[IfVersionCondition] = []
+    for tag in parse_if_version_tags(text):
+        if not isinstance(tag, IfVersionTag) or tag.closing:
+            continue
+        repository_value = tag.attribute("repository")
+        candidate = tag.attribute("containsPullRequest")
+        assert isinstance(repository_value, str)
+        repository = parse_github_repository_url(repository_value)
+        assert repository is not None
+        assert isinstance(candidate, int)
+        result.append(
+            IfVersionCondition(
+                repository=repository,
+                contains_pull_request=candidate,
+                span=tag.span,
+            )
+        )
+    return tuple(result)
+
+
+def contexts(text: str):
+    return map_snippet_condition_contexts(
+        parse_snippet_tags(text),
+        parse_if_version_tags(text),
+        conditions(text),
+    )
+
+
+def test_maps_unconditional_snippet_to_no_condition() -> None:
+    result = contexts('<Snippet source="ref" language="yaml" />')
+
+    assert len(result) == 1
+    assert result[0].condition is None
+
+
+def test_maps_both_branches_to_enclosing_condition() -> None:
+    result = contexts(
+        """<IfVersion repository="https://github.com/example/outer" containsPullRequest={12}>
+<Snippet source="new" language="yaml" />
+<Else>
+<Snippet source="old" language="yaml" />
+</Else>
+</IfVersion>"""
+    )
+
+    assert [context.condition.contains_pull_request for context in result] == [
+        12,
+        12,
+    ]
+
+
+def test_maps_nested_snippet_to_innermost_condition() -> None:
+    result = contexts(
+        """<IfVersion repository="https://github.com/example/outer" containsPullRequest={12}>
+<IfVersion repository="https://github.com/example/inner" containsPullRequest={34}>
+<Snippet source="nested" language="yaml" />
+</IfVersion>
+</IfVersion>"""
+    )
+
+    assert result[0].condition is not None
+    assert result[0].condition.repository == "example/inner"
+    assert result[0].condition.contains_pull_request == 34