# HG changeset patch
# User Pulkit Goyal <7895pulkit@gmail.com>
# Date 1607936881 -19800
# Node ID 4d1cec4e5e1fe4e4d9379954fbedd5c8d302aa99
# Parent  85f7cf314b39ac49028008b4b4a4e2f4f663a4ea
engine: unwrap a hard to understand for loop

The loop was iterating over all the datafiles and maintaining a set to check
whether filelogs have been processed, manifests have been processed or not.

The code was hard to understand and it assumed that `alldatafiles` are ordered
in a certain way.

This refactors the for loop in separate parts for each manifests, changelog and
filelogs. This will also help in future work where we will like more better
handling on whether we want to upgrade filelogs or not.

Differential Revision: https://phab.mercurial-scm.org/D9580

diff -r 85f7cf314b39 -r 4d1cec4e5e1f mercurial/upgrade_utils/engine.py
--- a/mercurial/upgrade_utils/engine.py	Mon Dec 14 14:18:38 2020 +0530
+++ b/mercurial/upgrade_utils/engine.py	Mon Dec 14 14:38:01 2020 +0530
@@ -184,6 +184,12 @@
     cdstsize = 0
 
     alldatafiles = list(srcrepo.store.walk())
+    # mapping of data files which needs to be cloned
+    # key is unencoded filename
+    # value is revlog_object_from_srcrepo
+    manifests = {}
+    changelogs = {}
+    filelogs = {}
 
     # Perform a pass to collect metadata. This validates we can open all
     # source files and allows a unified progress bar to be displayed.
@@ -209,15 +215,18 @@
 
         # This is for the separate progress bars.
         if isinstance(rl, changelog.changelog):
+            changelogs[unencoded] = rl
             crevcount += len(rl)
             csrcsize += datasize
             crawsize += rawsize
         elif isinstance(rl, manifest.manifestrevlog):
+            manifests[unencoded] = rl
             mcount += 1
             mrevcount += len(rl)
             msrcsize += datasize
             mrawsize += rawsize
         elif isinstance(rl, filelog.filelog):
+            filelogs[unencoded] = rl
             fcount += 1
             frevcount += len(rl)
             fsrcsize += datasize
@@ -248,86 +257,21 @@
 
     sidedatacompanion = getsidedatacompanion(srcrepo, dstrepo)
 
-    # Do the actual copying.
-    # FUTURE this operation can be farmed off to worker processes.
-    seen = set()
-    for unencoded, encoded, size in alldatafiles:
-        if unencoded.endswith(b'.d'):
-            continue
-
-        oldrl = _revlogfrompath(srcrepo, unencoded)
-
-        if isinstance(oldrl, changelog.changelog) and b'c' not in seen:
-            ui.status(
-                _(
-                    b'finished migrating %d manifest revisions across %d '
-                    b'manifests; change in size: %s\n'
-                )
-                % (mrevcount, mcount, util.bytecount(mdstsize - msrcsize))
-            )
-
-            ui.status(
-                _(
-                    b'migrating changelog containing %d revisions '
-                    b'(%s in store; %s tracked data)\n'
-                )
-                % (
-                    crevcount,
-                    util.bytecount(csrcsize),
-                    util.bytecount(crawsize),
-                )
-            )
-            seen.add(b'c')
-            progress = srcrepo.ui.makeprogress(
-                _(b'changelog revisions'), total=crevcount
-            )
-        elif isinstance(oldrl, manifest.manifestrevlog) and b'm' not in seen:
-            ui.status(
-                _(
-                    b'finished migrating %d filelog revisions across %d '
-                    b'filelogs; change in size: %s\n'
-                )
-                % (frevcount, fcount, util.bytecount(fdstsize - fsrcsize))
-            )
-
-            ui.status(
-                _(
-                    b'migrating %d manifests containing %d revisions '
-                    b'(%s in store; %s tracked data)\n'
-                )
-                % (
-                    mcount,
-                    mrevcount,
-                    util.bytecount(msrcsize),
-                    util.bytecount(mrawsize),
-                )
-            )
-            seen.add(b'm')
-            if progress:
-                progress.complete()
-            progress = srcrepo.ui.makeprogress(
-                _(b'manifest revisions'), total=mrevcount
-            )
-        elif b'f' not in seen:
-            ui.status(
-                _(
-                    b'migrating %d filelogs containing %d revisions '
-                    b'(%s in store; %s tracked data)\n'
-                )
-                % (
-                    fcount,
-                    frevcount,
-                    util.bytecount(fsrcsize),
-                    util.bytecount(frawsize),
-                )
-            )
-            seen.add(b'f')
-            if progress:
-                progress.complete()
-            progress = srcrepo.ui.makeprogress(
-                _(b'file revisions'), total=frevcount
-            )
-
+    # Migrating filelogs
+    ui.status(
+        _(
+            b'migrating %d filelogs containing %d revisions '
+            b'(%s in store; %s tracked data)\n'
+        )
+        % (
+            fcount,
+            frevcount,
+            util.bytecount(fsrcsize),
+            util.bytecount(frawsize),
+        )
+    )
+    progress = srcrepo.ui.makeprogress(_(b'file revisions'), total=frevcount)
+    for unencoded, oldrl in sorted(filelogs.items()):
         newrl = _perform_clone(
             ui,
             dstrepo,
@@ -342,18 +286,94 @@
         )
         info = newrl.storageinfo(storedsize=True)
         datasize = info[b'storedsize'] or 0
-
         dstsize += datasize
+        fdstsize += datasize
+    ui.status(
+        _(
+            b'finished migrating %d filelog revisions across %d '
+            b'filelogs; change in size: %s\n'
+        )
+        % (frevcount, fcount, util.bytecount(fdstsize - fsrcsize))
+    )
 
-        if isinstance(newrl, changelog.changelog):
-            cdstsize += datasize
-        elif isinstance(newrl, manifest.manifestrevlog):
-            mdstsize += datasize
-        else:
-            fdstsize += datasize
+    # Migrating manifests
+    ui.status(
+        _(
+            b'migrating %d manifests containing %d revisions '
+            b'(%s in store; %s tracked data)\n'
+        )
+        % (
+            mcount,
+            mrevcount,
+            util.bytecount(msrcsize),
+            util.bytecount(mrawsize),
+        )
+    )
+    if progress:
+        progress.complete()
+    progress = srcrepo.ui.makeprogress(
+        _(b'manifest revisions'), total=mrevcount
+    )
+    for unencoded, oldrl in sorted(manifests.items()):
+        newrl = _perform_clone(
+            ui,
+            dstrepo,
+            tr,
+            oldrl,
+            unencoded,
+            deltareuse,
+            forcedeltabothparents,
+            revlogs,
+            sidedatacompanion,
+            oncopiedrevision,
+        )
+        info = newrl.storageinfo(storedsize=True)
+        datasize = info[b'storedsize'] or 0
+        dstsize += datasize
+        mdstsize += datasize
+    ui.status(
+        _(
+            b'finished migrating %d manifest revisions across %d '
+            b'manifests; change in size: %s\n'
+        )
+        % (mrevcount, mcount, util.bytecount(mdstsize - msrcsize))
+    )
 
+    # Migrating changelog
+    ui.status(
+        _(
+            b'migrating changelog containing %d revisions '
+            b'(%s in store; %s tracked data)\n'
+        )
+        % (
+            crevcount,
+            util.bytecount(csrcsize),
+            util.bytecount(crawsize),
+        )
+    )
+    if progress:
+        progress.complete()
+    progress = srcrepo.ui.makeprogress(
+        _(b'changelog revisions'), total=crevcount
+    )
+    for unencoded, oldrl in sorted(changelogs.items()):
+        newrl = _perform_clone(
+            ui,
+            dstrepo,
+            tr,
+            oldrl,
+            unencoded,
+            deltareuse,
+            forcedeltabothparents,
+            revlogs,
+            sidedatacompanion,
+            oncopiedrevision,
+        )
+        info = newrl.storageinfo(storedsize=True)
+        datasize = info[b'storedsize'] or 0
+        dstsize += datasize
+        cdstsize += datasize
     progress.complete()
-
     ui.status(
         _(
             b'finished migrating %d changelog revisions; change in size: '