lib.FileContext.put(): Add parameter "atomic"

Add the parameter "atomic" to put() / _put(). If instructs the
implementation to take extra precautions to make sure the operation
either succeeds or fails entirely, i.e. doesn't leave a broken target
file behind.

Signed-off-by: Jan Lindemann <jan@janware.com>

src/python/jw/pkg/lib/ExecContext.py

@@ -292,6 +292,7 @@ class ExecContext(Base):
         owner: str|None,
         group: str|None,
         mode: str|None,
+        atomic: bool,
     ) -> Result:
 
         from .util import pretty_cmd
@@ -303,18 +304,19 @@ class ExecContext(Base):
         try:
             if wd is not None:
                 path = wd + '/' + path
-            tmp = (await __run(['mktemp', path + '.XXXXXX'])).stdout.decode().strip()
             cmds: list[dict[str, str|list[str]|bool]] = []
-            cmds.append({'cmd': ['tee', tmp], 'cmd_input': content})
+            out = (await __run(['mktemp', path + '.XXXXXX'])).stdout.decode().strip() if atomic else path
+            cmds.append({'cmd': ['tee', out], 'cmd_input': content})
             if owner is not None and group is not None:
-                cmds.append({'cmd': ['chown', f'{owner}:{group}', tmp]})
+                cmds.append({'cmd': ['chown', f'{owner}:{group}', out]})
             elif owner is not None:
-                cmds.append({'cmd': ['chown', owner, tmp]})
+                cmds.append({'cmd': ['chown', owner, out]})
             elif group is not None:
-                cmds.append({'cmd': ['chgrp', group, tmp]})
+                cmds.append({'cmd': ['chgrp', group, out]})
             if mode is not None:
-                cmds.append({'cmd': ['chmod', mode, tmp]})
-            cmds.append({'cmd': ['mv', tmp, path]})
+                cmds.append({'cmd': ['chmod', mode, out]})
+            if atomic:
+                cmds.append({'cmd': ['mv', out, path]})
             for cmd in cmds:
                 log(DEBUG, f'{self.log_name}: Running {pretty_cmd(cmd['cmd'], wd)}')
                 ret = await __run(**cmd)

src/python/jw/pkg/lib/FileContext.py

@@ -88,6 +88,7 @@ class FileContext(abc.ABC):
         owner: str|None,
         group: str|None,
         mode: str|None,
+        atomic: bool,
     ) -> Result:
         raise NotImplementedError()
 
@@ -98,13 +99,14 @@ class FileContext(abc.ABC):
         wd: str|None = None,
         throw: bool = True,
         verbose: bool|None = None,
-        title: str=None,
-        owner: str|None=None,
-        group: str|None=None,
-        mode: str|None=None,
+        title: str = None,
+        owner: str|None = None,
+        group: str|None = None,
+        mode: str|None = None,
+        atomic: bool = False
     ) -> Result:
         return await self._put(content, path, wd=wd, throw=throw, verbose=verbose,
-                               title=title, owner=owner, group=group, mode=mode)
+                               title=title, owner=owner, group=group, mode=mode, atomic=atomic)
 
     async def _close(self) -> None:
         pass

src/python/jw/pkg/lib/ec/Curl.py

@@ -44,17 +44,3 @@ class Curl(Base):
             path = '/' + path
         cmd.append(self.__base_url + path)
         return await self.__ec.run(cmd, throw=throw, verbose=verbose)
-
-    async def _put(
-        self,
-        content: bytes,
-        path: str,
-        wd: str|None,
-        throw: bool,
-        verbose: bool|None,
-        title: str,
-        owner: str|None,
-        group: str|None,
-        mode: str|None,
-    ) -> Result:
-        raise NotImplementedError()