fix: strip # prefix from tags in isTaskFile for tag-based identification

[victoraraujo105]

Summary

• isTaskFile fails to match tasks when using tag-based identification because Obsidian's metadata cache prepends # to frontmatter tag values
• tags: [task] in YAML becomes ["#task"] in cache.frontmatter.tags, causing matchesHierarchicalTagExact("#task", "task") to return false
• Fix: strip the # prefix before passing to matchesHierarchicalTagExact

Reproduction

1. Set task identification to "tag" method with taskTag: "task" (the default at src/settings/defaults.ts:262)
2. Create a task file with tags: [task] in frontmatter (either via the plugin UI or tn create)
3. Run the following in the Obsidian developer console to observe the bug:

// Check what the metadata cache returns for tags
const file = app.vault.getMarkdownFiles().find(f => f.path.includes('TaskNotes/Tasks/'));
const cache = app.metadataCache.getFileCache(file);
console.log(cache.frontmatter.tags);
// Output: ["#task", ...] -- note the '#' prefix added by Obsidian

// Check what taskTag is set to
console.log(app.plugins.plugins['tasknotes'].settings.taskTag);
// Output: "task" -- no '#' prefix

// The comparison "#task" !== "task" always fails

4. Observe that tn list returns 0 tasks despite files existing on disk:

# Create a task
tn create "Test task today #planning 15m"
# Output: Task created successfully!

# List tasks -- returns 0 because isTaskFile fails
tn list
# Output: Found 0 tasks

5. After applying this fix, tn list correctly returns the created task.

Root cause

TaskManager.isTaskFile() at src/utils/TaskManager.ts:103 passes raw frontmatter.tags values (which include the # prefix from Obsidian's metadata cache) directly to FilterUtils.matchesHierarchicalTagExact(), which does an exact string comparison without accounting for the prefix.

Before fix:

return frontmatter.tags.some((tag: string) =>
    typeof tag === 'string' && FilterUtils.matchesHierarchicalTagExact(tag, this.taskTag)
);
// matchesHierarchicalTagExact("#task", "task") => false

After fix:

return frontmatter.tags.some((tag: string) => {
    if (typeof tag !== 'string') return false;
    const cleanTag = tag.startsWith('#') ? tag.slice(1) : tag;
    return FilterUtils.matchesHierarchicalTagExact(cleanTag, this.taskTag);
});
// matchesHierarchicalTagExact("task", "task") => true

Tests

Added 23 tests in tests/unit/utils/TaskManager.isTaskFile.test.ts covering:

• Obsidian metadata cache tags (with # prefix) -- the primary bug scenario
• Raw frontmatter tags (without # prefix) -- backward compatibility
• Mixed tag formats -- both #-prefixed and plain tags in same array
• Hierarchical tags -- #task/project matching task
• Case insensitivity -- #Task matching task
• Edge cases -- null/undefined frontmatter, non-array tags, non-string values, empty arrays, double-hash (##task), bare #

All 23 tests pass. No pre-existing tests were affected.

Test plan

• isTaskFile returns true for tags: ["#task"] when taskTag is "task"
• isTaskFile still works for tags without # prefix
• Hierarchical tag matching works (e.g., #task/subtask matches task)
• Case-insensitive matching works
• Edge cases handled (null, undefined, non-string, empty)
• Full test suite passes with no regressions (same 9 pre-existing failures on main)