[PATCH] grep: warn on censored revisions instead of erroring out

[Jordi Gutiérrez Hermoso]

# HG changeset patch
# User Jordi Gutiérrez Hermoso <jordigh at octave.org>
# Date 1571688404 14400
#      Mon Oct 21 16:06:44 2019 -0400
# Node ID 608193de8560218cc27032977bc380cb8dc0f3f8
# Parent  d782cce137fd1d50cccfecf8ccb17a623fde8800
grep: warn on censored revisions instead of erroring out

We need most of the grep logic to go through in case we encounter a
censored revision, so we just return a None body for a censored node,
and we stop just short of trying to record matches with the contents
of that censored body. The other parts such as recording that the
censored file has been considered at this revision needs to go into
the proper dicts.

I have also gotten weary of all the abbreviations, so while I did a
small refactor to move the file-data-getting operation into a common
function, I also expanded the abbreviations of the relevant variables
within this little function. Hopefully some day this helps someone
figure out what all the abbreviations mean.

diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -3440,6 +3440,9 @@ def grep(ui, repo, pattern, *pats, **opt
     def grepbody(fn, rev, body):
         matches[rev].setdefault(fn, [])
         m = matches[rev][fn]
+        if body is None:
+            return
+
         for lnum, cstart, cend, line in matchlines(body):
             s = linestate(line, lnum, cstart, cend)
             m.append(s)
@@ -3575,6 +3578,22 @@ def grep(ui, repo, pattern, *pats, **opt
 
     getrenamed = scmutil.getrenamedfn(repo)
 
+    def get_file_content(filename, filelog, filenode, context, revision):
+        try:
+            content = filelog.read(filenode)
+        except error.WdirUnsupported:
+            content = context[filename].data()
+        except error.CensoredNodeError:
+            content = None
+            ui.warn(
+                _(b'Cannot search in censored file: %(filename)s:%(revnum)s\n')
+                % {
+                    'filename': pycompat.bytestr(filename),
+                    'revnum': pycompat.bytestr(revision),
+                }
+            )
+        return content
+
     def prep(ctx, fns):
         rev = ctx.rev()
         pctx = ctx.p1()
@@ -3601,17 +3620,15 @@ def grep(ui, repo, pattern, *pats, **opt
             files.append(fn)
 
             if fn not in matches[rev]:
-                try:
-                    content = flog.read(fnode)
-                except error.WdirUnsupported:
-                    content = ctx[fn].data()
+                content = get_file_content(fn, flog, fnode, ctx, rev)
                 grepbody(fn, rev, content)
 
             pfn = copy or fn
             if pfn not in matches[parent]:
                 try:
-                    fnode = pctx.filenode(pfn)
-                    grepbody(pfn, parent, flog.read(fnode))
+                    pfnode = pctx.filenode(pfn)
+                    pcontent = get_file_content(pfn, flog, pfnode, pctx, parent)
+                    grepbody(pfn, parent, pcontent)
                 except error.LookupError:
                     pass