76 lines
2.7 KiB
Python
76 lines
2.7 KiB
Python
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"""Schema 2: a document holds symbols, not timelines, and no symbol is reserved.
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Three renames, each in the stored transit and nowhere else:
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clip/<cid>/timeline/... -> clip/<cid>/symbol/...
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a node leaf's :kind :symbol -> :kind :instance
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a feature leaf's :timeline key -> :symbol
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A leaf value is transit's map form, ["^ ", k1, v1, k2, v2, ...]. Only TOP-LEVEL
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pairs are rewritten, and only literal ones: transit caches a repeated keyword as
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"^N", and a rename that met a cache reference where it expected the keyword would
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be guessing. Every saved leaf at the time of writing had these as literals; if one
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does not, the migration stops rather than writing a document that decodes to
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something else.
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Renaming a cached keyword in place is safe because the cache is positional: the
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literal keeps its slot, so any later "^N" that referred to it now refers to the
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new name, which is what it meant.
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"""
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import re
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from django.db import migrations, models
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PATH = re.compile(r"^(clip/[^/]+/)timeline(/|$)")
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def _rename_pair(value, key, old, new, path):
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if not (isinstance(value, list) and value[:1] == ["^ "]):
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return value
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out = list(value)
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for i in range(1, len(out) - 1, 2):
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if out[i] != key:
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continue
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if old is None:
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out[i] = new
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elif out[i + 1] == old:
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out[i + 1] = new
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elif isinstance(out[i + 1], str) and out[i + 1].startswith("^") and out[i + 1] != "^ ":
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raise RuntimeError(f"leaf {path!r} has a cached {key} value; migrate it by hand")
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return out
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def forwards(apps, schema_editor):
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Leaf = apps.get_model("clips", "Leaf")
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Project = apps.get_model("clips", "Project")
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for leaf in Leaf.objects.all():
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path = PATH.sub(r"\1symbol\2", leaf.path)
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value = leaf.value
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parts = path.split("/")
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if len(parts) == 6 and parts[2] == "symbol" and parts[4] == "node":
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value = _rename_pair(value, "~:kind", "~:symbol", "~:instance", leaf.path)
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if len(parts) == 4 and parts[2] == "feature":
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value = _rename_pair(value, "~:timeline", None, "~:symbol", leaf.path)
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if path != leaf.path or value != leaf.value:
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leaf.path = path
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leaf.value = value
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leaf.version += 1
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leaf.save(update_fields=["path", "value", "version"])
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Project.objects.update(schema_version=2)
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class Migration(migrations.Migration):
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dependencies = [
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("clips", "0006_project_schema_version"),
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]
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operations = [
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migrations.AlterField(
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model_name="project",
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name="schema_version",
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field=models.PositiveIntegerField(default=2),
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),
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migrations.RunPython(forwards, migrations.RunPython.noop),
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]
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