Hack to support reuse of memory command, closes #643

docs/plugins.rst

@@ -115,6 +115,31 @@ Example implementation:
             "Say hello world"
             click.echo("Hello world!")
 
+New commands implemented by plugins can invoke existing commands using the `context.invoke <https://click.palletsprojects.com/en/stable/api/#click.Context.invoke>`__ mechanism.
+
+As a special niche feature, if your plugin needs to import some files and then act against an in-memory database containing those files you can forward to the :ref:`sqlite-utils memory command <cli_memory>` and then access a named in-memory database called ``sqlite_utils_memory`` like this:
+
+.. code-block:: python
+
+    from contextlib import redirect_stdout
+    import io
+
+    @cli.command()
+    @click.pass_context
+    @click.argument(
+        "paths",
+        type=click.Path(file_okay=True, dir_okay=False, allow_dash=True),
+        required=False,
+        nargs=-1,
+    )
+    def show_schema_for_files(ctx, paths):
+        from sqlite_utils.cli import memory
+        with redirect_stdout(io.StringIO()):
+            ctx.invoke(memory, paths=paths, sql="select 1")
+        db = sqlite_utils.Database(memory_name="sqlite_utils_memory")
+        # Now do something with that database
+        click.echo(db.schema)
+
 .. _plugins_hooks_prepare_connection:
 
 prepare_connection(conn)

sqlite_utils/cli.py

@@ -1815,6 +1815,10 @@ def query(
     )
 
 
+# So named memory db "sqlite_utils_memory" isn't dropped when it goes out of scope
+_sqlite_utils_memory_db = []
+
+
 @cli.command()
 @click.argument(
     "paths",
@@ -1921,7 +1925,14 @@ def memory(
     \b
         sqlite-utils memory animals.csv --schema
     """
-    db = sqlite_utils.Database(memory=True)
+    if getattr(sys, "_sqlite_utils_memory_test", False) or not getattr(
+        sys, "_called_from_test", False
+    ):
+        db = sqlite_utils.Database(memory_name="sqlite_utils_memory")
+        _sqlite_utils_memory_db.append(db)
+    else:
+        db = sqlite_utils.Database(memory=True)
+
     # If --dump or --save or --analyze used but no paths detected, assume SQL query is a path:
     if (dump or save or schema or analyze) and not paths:
         paths = [sql]
@@ -1954,6 +1965,7 @@ def memory(
             rows = tracker.wrap(rows)
         if flatten:
             rows = (_flatten(row) for row in rows)
+
         db[file_table].insert_all(rows, alter=True)
         if tracker is not None:
             db[file_table].transform(types=tracker.types)
@@ -1964,6 +1976,7 @@ def memory(
         for view_name in view_names:
             if not db[view_name].exists():
                 db.create_view(view_name, "select * from [{}]".format(file_table))
+
         if fp:
             fp.close()
 

sqlite_utils/db.py

@@ -325,6 +325,8 @@ class Database:
         execute_plugins: bool = True,
         strict: bool = False,
     ):
+        self.memory_name = None
+        self.memory = False
         assert (filename_or_conn is not None and (not memory and not memory_name)) or (
             filename_or_conn is None and (memory or memory_name)
         ), "Either specify a filename_or_conn or pass memory=True"
@@ -335,8 +337,11 @@ class Database:
                 uri=True,
                 check_same_thread=False,
             )
+            self.memory = True
+            self.memory_name = memory_name
         elif memory or filename_or_conn == ":memory:":
             self.conn = sqlite3.connect(":memory:")
+            self.memory = True
         elif isinstance(filename_or_conn, (str, pathlib.Path)):
             if recreate and os.path.exists(filename_or_conn):
                 try:

tests/test_cli_memory.py

@@ -1,6 +1,6 @@
 import json
-
 import pytest
+import sys
 from click.testing import CliRunner
 
 from sqlite_utils import Database, cli
@@ -305,3 +305,23 @@ def test_memory_functions():
     )
     assert result.exit_code == 0
     assert result.output.strip() == '[{"hello()": "Hello"}]'
+
+
+@pytest.mark.parametrize("enabled", (False, True))
+def test_memory_named_database_hack(enabled):
+    # https://github.com/simonw/sqlite-utils/issues/643
+    sys._sqlite_utils_memory_test = enabled
+    try:
+        result = CliRunner().invoke(
+            cli.cli,
+            ["memory", "-", "--analyze"],
+            input="id,name\n1,Cleo\n2,Bants",
+        )
+        assert result.exit_code == 0
+        db = Database(memory_name="sqlite_utils_memory")
+        if enabled:
+            assert db.table_names() == ["stdin"]
+        else:
+            assert db.table_names() == []
+    finally:
+        sys._sqlite_utils_memory_test = False