First working implementation of dump command

Author: simonw

README.md

@@ -6,4 +6,8 @@
 
 Tools for dumping/loading a SQLite database to diffable directory structure
 
-Work in progress.
+Usage:
+
+    $ sqlite-diffable dump fixtures.db out/ facetable
+
+This dumps the table called "facetable" from fixtures.db into the out/ directory.

setup.py

@@ -26,7 +26,7 @@ def get_long_description():
     extras_require={"test": ["pytest", "black"]},
     entry_points="""
         [console_scripts]
-        sqlite-diffadble=sqlite_diffable.cli:cli
+        sqlite-diffable=sqlite_diffable.cli:cli
     """,
     tests_require=["sqlite-diffable[test]"],
     url="https://github.com/simonw/sqlite-diffable",

sqlite_diffable/cli.py

@@ -1,8 +1,44 @@
 import click
+import json
+import pathlib
+import sqlite_utils
 
 
 @click.group()
 @click.version_option()
 def cli():
     "Tools for dumping/loading a SQLite database to diffable directory structure"
     pass
+
+
+@cli.command()
+@click.argument(
+    "path", type=click.Path(exists=True, file_okay=True, dir_okay=False), required=True
+)
+@click.argument(
+    "output", type=click.Path(file_okay=False, dir_okay=True), required=True
+)
+@click.argument("tables", nargs=-1, required=True)
+def dump(path, output, tables):
+    output = pathlib.Path(output)
+    output.mkdir(exist_ok=True)
+    conn = sqlite_utils.Database(path)
+    for table in tables:
+        filepath = output / "{}.ndjson".format(table)
+        metapath = output / "{}.metadata.json".format(table)
+        # Dump rows to filepath
+        with filepath.open("w") as fp:
+            for row in conn[table].rows:
+                fp.write(json.dumps(list(row.values())) + "\n")
+            fp.close()
+        # Dump out metadata
+        metapath.open("w").write(
+            json.dumps(
+                {
+                    "name": table,
+                    "columns": [c.name for c in conn[table].columns],
+                    "schema": conn[table].schema,
+                },
+                indent=4,
+            )
+        )

tests/conftest.py

@@ -0,0 +1,17 @@
+import pytest
+import sqlite_utils
+
+
+@pytest.fixture
+def one_table_db(tmpdir):
+    path = str(tmpdir / "one_table.db")
+    db = sqlite_utils.Database(path)
+    db["one_table"].insert_all(
+        [
+            {"id": 1, "name": "Stacey"},
+            {"id": 2, "name": "Tilda"},
+            {"id": 3, "name": "Bartek"},
+        ],
+        pk="id",
+    )
+    return path

tests/test_dump.py

@@ -1,2 +1,24 @@
-def test_dump():
-    assert False
+from click.testing import CliRunner
+from sqlite_diffable import cli
+import json
+
+
+def test_dump(one_table_db, tmpdir):
+    output_dir = tmpdir / "out"
+    result = CliRunner().invoke(
+        cli.cli, ["dump", one_table_db, str(output_dir), "one_table"]
+    )
+    assert 0 == result.exit_code, result.output
+    # out/ should now have a single file in it
+    ndjson = output_dir / "one_table.ndjson"
+    metadata = output_dir / "one_table.metadata.json"
+    assert ndjson.exists()
+    assert metadata.exists()
+    assert [[1, "Stacey"], [2, "Tilda"], [3, "Bartek"]] == [
+        json.loads(line) for line in ndjson.open()
+    ]
+    assert {
+        "name": "one_table",
+        "columns": ["id", "name"],
+        "schema": "CREATE TABLE [one_table] (\n   [id] INTEGER PRIMARY KEY,\n   [name] TEXT\n)",
+    } == json.load(metadata)