Allow append mode for ZIP (#1453)

Author: martindurant

fsspec/implementations/local.py

@@ -386,6 +386,9 @@ def readlines(self, *args, **kwargs):
     def close(self):
         return self.f.close()
 
+    def truncate(self, size=None) -> int:
+        return self.f.truncate(size)
+
     @property
     def closed(self):
         return self.f.closed

fsspec/implementations/tests/test_zip.py

@@ -94,3 +94,29 @@ def test_zip_glob_star(m):
     fs, _ = fsspec.core.url_to_fs("zip::memory://out.zip")
     outfiles = fs.glob("*")
     assert len(outfiles) == 1
+
+
+def test_append(m, tmpdir):
+    fs = fsspec.filesystem("zip", fo="memory://out.zip", mode="w")
+    with fs.open("afile", "wb") as f:
+        f.write(b"data")
+    fs.close()
+
+    fs = fsspec.filesystem("zip", fo="memory://out.zip", mode="a")
+    with fs.open("bfile", "wb") as f:
+        f.write(b"data")
+    fs.close()
+
+    assert len(fsspec.open_files("zip://*::memory://out.zip")) == 2
+
+    fs = fsspec.filesystem("zip", fo=f"{tmpdir}/out.zip", mode="w")
+    with fs.open("afile", "wb") as f:
+        f.write(b"data")
+    fs.close()
+
+    fs = fsspec.filesystem("zip", fo=f"{tmpdir}/out.zip", mode="a")
+    with fs.open("bfile", "wb") as f:
+        f.write(b"data")
+    fs.close()
+
+    assert len(fsspec.open_files("zip://*::memory://out.zip")) == 2

fsspec/implementations/zip.py

@@ -49,8 +49,12 @@ def __init__(
             raise ValueError(f"mode '{mode}' no understood")
         self.mode = mode
         if isinstance(fo, str):
+            if mode == "a":
+                m = "r+b"
+            else:
+                m = mode + "b"
             fo = fsspec.open(
-                fo, mode=mode + "b", protocol=target_protocol, **(target_options or {})
+                fo, mode=m, protocol=target_protocol, **(target_options or {})
             )
         self.of = fo
         self.fo = fo.__enter__()  # the whole instance is a context