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fix: move BlockKey and derived_key to avoid cyclical import
After we merged this PR: openedx#33920 this error began popping up in logs: Unable to load XBlock 'staffgradedxblock' .... ImportError: cannot import name 'get_course_blocks' from partially initialized module 'lms.djangoapps.course_blocks.api' (most likely due to a circular import) ... The root cause was the new imports of `derived_key` and `BlockKey` into xmodule/library_content_block.py. Those new imports come from xmodule/modulestore/store_utilities.py, which runs `XBlock.load_classes()` at the module level, which fails because we are still in the process of loading xmodule/library_content_block. As a solution, we move both `derived_key` and `BlockKey` to xmodule/util/keys.py. We could potentially move that file to opaque-keys eventually, depending on how well we think that those concepts generalize. Also: * We rename the function from derived_key to derive_key, as functions should be verbs. * We combine the first to parameters of derive_key (a source ContextKey and a source BlockKey) into a single parameter (a source UsageKey). In my opinion, this makes the function call easier to understand.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,22 +1,10 @@ | ||
| """ | ||
| General utilities | ||
| """ | ||
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| from collections import namedtuple | ||
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| from opaque_keys.edx.locator import BlockUsageLocator | ||
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| class BlockKey(namedtuple('BlockKey', 'type id')): # lint-amnesty, pylint: disable=missing-class-docstring | ||
| __slots__ = () | ||
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| def __new__(cls, type, id): # lint-amnesty, pylint: disable=redefined-builtin | ||
| return super().__new__(cls, type, id) | ||
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| @classmethod | ||
| def from_usage_key(cls, usage_key): | ||
| return cls(usage_key.block_type, usage_key.block_id) | ||
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| # We import BlockKey here for backwards compatibility with modulestore code. | ||
| # Feel free to remove this and fix the imports if you have time. | ||
| from xmodule.util.keys import BlockKey | ||
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| CourseEnvelope = namedtuple('CourseEnvelope', 'course_key structure') |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,45 @@ | ||
| """ | ||
| Tests for xmodule/util/keys.py | ||
| """ | ||
| import ddt | ||
| from unittest import TestCase | ||
| from unittest.mock import Mock | ||
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| from opaque_keys.edx.locator import BlockUsageLocator | ||
| from opaque_keys.edx.keys import CourseKey | ||
| from xmodule.util.keys import BlockKey, derive_key | ||
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| mock_block = Mock() | ||
| mock_block.id = CourseKey.from_string('course-v1:Beeper+B33P+BOOP') | ||
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| derived_key_scenarios = [ | ||
| { | ||
| 'source': BlockUsageLocator.from_string( | ||
| 'block-v1:edX+DemoX+Demo_Course+type@chapter+block@interactive_demonstrations' | ||
| ), | ||
| 'parent': mock_block, | ||
| 'expected': BlockKey('chapter', '5793ec64e25ed870a7dd'), | ||
| }, | ||
| { | ||
| 'source': BlockUsageLocator.from_string( | ||
| 'block-v1:edX+DemoX+Demo_Course+type@chapter+block@interactive_demonstrations' | ||
| ), | ||
| 'parent': BlockKey('chapter', 'thingy'), | ||
| 'expected': BlockKey('chapter', '599792a5622d85aa41e6'), | ||
| } | ||
| ] | ||
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| @ddt.ddt | ||
| class TestDeriveKey(TestCase): | ||
| """ | ||
| Test reproducible block ID generation. | ||
| """ | ||
| @ddt.data(*derived_key_scenarios) | ||
| @ddt.unpack | ||
| def test_derive_key(self, source, parent, expected): | ||
| """ | ||
| Test that derive_key returns the expected value. | ||
| """ | ||
| assert derive_key(source, parent) == expected |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,62 @@ | ||
| """ | ||
| Utilities for working with opaque-keys. | ||
| Consider moving these into opaque-keys if they generalize well. | ||
| """ | ||
| import hashlib | ||
| from typing import NamedTuple | ||
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| from opaque_keys.edx.keys import UsageKey | ||
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| class BlockKey(NamedTuple): | ||
| """ | ||
| A pair of strings (type, id) that uniquely identify an XBlock Usage within a LearningContext. | ||
| Put another way: LearningContextKey * BlockKey = UsageKey. | ||
| Example: | ||
| "course-v1:myOrg+myCourse+myRun" <- LearningContextKey string | ||
| ("html", "myBlock") <- BlockKey | ||
| "course-v1:myOrg+myCourse+myRun+type@html+block@myBlock" <- UsageKey string | ||
| """ | ||
| type: str | ||
| id: str | ||
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| @classmethod | ||
| def from_usage_key(cls, usage_key): | ||
| return cls(usage_key.block_type, usage_key.block_id) | ||
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| def derive_key(source: UsageKey, dest_parent: BlockKey) -> BlockKey: | ||
| """ | ||
| Return a new reproducible BlockKey for a given source usage and destination parent block. | ||
| When recursively copying a block structure, we need to generate new block IDs for the | ||
| blocks. We don't want to use the exact same IDs as we might copy blocks multiple times. | ||
| However, we do want to be able to reproduce the same IDs when copying the same block | ||
| so that if we ever need to re-copy the block from its source (that is, to update it with | ||
| upstream changes) we don't affect any data tied to the ID, such as grades. | ||
| This is used by the copy_from_template function of the modulestore, and can be used by | ||
| pluggable django apps that need to copy blocks from one course to another in an | ||
| idempotent way. In the future, this should be created into a proper API function | ||
| in the spirit of OEP-49. | ||
| """ | ||
| source_context = source.context_key | ||
| if hasattr(source_context, 'for_version'): | ||
| source_context = source_context.for_version(None) | ||
| # Compute a new block ID. This new block ID must be consistent when this | ||
| # method is called with the same (source, dest_parent) pair. | ||
| # Note: years after this was written, mypy pointed out that the way we are | ||
| # encoding & formatting the source context means it looks like b'....', ie | ||
| # it literally contains the character 'b' and single quotes within the unique_data | ||
| # string. So that's a little silly, but it's fine, and we can't change it now. | ||
| unique_data = "{}:{}:{}".format( | ||
| str(source_context).encode("utf-8"), # type: ignore[str-bytes-safe] | ||
| source.block_id, | ||
| dest_parent.id, | ||
| ) | ||
| new_block_id = hashlib.sha1(unique_data.encode('utf-8')).hexdigest()[:20] | ||
| return BlockKey(source.block_type, new_block_id) |