On Thu, Sep 06 2018, Tim Schumacher wrote:
> Aliases can only contain non-alias git commands and their
> arguments, not other user-defined aliases. Resolving further
> (nested) aliases is prevented by breaking the loop after the
> first alias was processed. Git then fails with a command-not-found
> error.
>
> Allow resolving nested aliases by not breaking the loop in
> run_argv() after the first alias was processed. Instead, continue
> incrementing `done_alias` until `handle_alias()` fails, which means that
> there are no further aliases that can be processed. Prevent looping
> aliases by storing substituted commands in `cmd_list` and checking if
> a command has been substituted previously.
>
> While we're at it, fix a styling issue just below the added code.
> ---
> git.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/git.c b/git.c
> index c27c38738..64f5fbd57 100644
> --- a/git.c
> +++ b/git.c
> @@ -674,6 +674,7 @@ static void execv_dashed_external(const char **argv)
> static int run_argv(int *argcp, const char ***argv)
> {
> int done_alias = 0;
> + struct string_list cmd_list = STRING_LIST_INIT_NODUP;
>
> while (1) {
> /*
> @@ -691,17 +692,23 @@ static int run_argv(int *argcp, const char ***argv)
> /* .. then try the external ones */
> execv_dashed_external(*argv);
>
> - /* It could be an alias -- this works around the insanity
> + if (string_list_has_string(&cmd_list, *argv[0]))
> + die(_("loop alias: %s is called twice"), *argv[0]);
> +
> + string_list_append(&cmd_list, *argv[0]);
> +
> + /*
> + * It could be an alias -- this works around the insanity
> * of overriding "git log" with "git show" by having
> * alias.log = show
> */
> - if (done_alias)
> - break;
> if (!handle_alias(argcp, argv))
> break;
> - done_alias = 1;
> + done_alias++;
> }
>
> + string_list_clear(&cmd_list, 0);
> +
> return done_alias;
> }
[In my just-sent
https://public-inbox.org/git/87r2i6rbiy.fsf@xxxxxxxxxxxxxxxxxxx/ I
should have said "the v3 thread"]
Thanks for working on this, comments:
If we don't have some test for these sort of aliasing loops that fails
now, we really should add that in a 1/2 and fix it in this patch in 2/2.
This error reporting is quite bad, consider:
[alias]
foo = bar
bar = baz
baz = foo
We then say:
$ ./git --exec-path=$PWD foo
fatal: loop alias: bar is called twice
That makes sense from an implementaion perspective, i.e. we lookup "bar"
twice. But let's do better. If I have aliase like:
a = b
b = c
c = d
d = e
e = c
It should be telling me that my "e" expansion looped back to the "c = d"
expansion. Here's a patch to implement that, feel free to either squash
it in with my Signed-Off-By, or tacked onto a v4 version of this,
whichever you think makes sense:
diff --git a/git.c b/git.c
index 64f5fbd572..38f1033e52 100644
--- a/git.c
+++ b/git.c
@@ -692,8 +692,64 @@ static int run_argv(int *argcp, const char ***argv)
/* .. then try the external ones */
execv_dashed_external(*argv);
- if (string_list_has_string(&cmd_list, *argv[0]))
- die(_("loop alias: %s is called twice"), *argv[0]);
+ if (string_list_has_string(&cmd_list, *argv[0])) {
+ struct strbuf sb = STRBUF_INIT;
+ int i, seen_at_idx = -1;
+
+ /*
+ * Find the re-entry point for the alias
+ * loop. TODO: There really should be a
+ * "return the index of the first matching"
+ * helper in string-list.c.
+ */
+ for (i = 0; i < cmd_list.nr; i++) {
+ if (!strcmp(*argv[0], cmd_list.items[i].string))
+ seen_at_idx = i;
+ }
+ assert(seen_at_idx != -1);
+
+ for (i = 1; i < cmd_list.nr; i++) {
+ if (i - 1 == seen_at_idx)
+ /*
+ * TRANSLATORS: This is a the
+ * re-enttry point in the list
+ * printed out by the "alias
+ * loop" message below.
+ */
+ strbuf_addf(&sb, _(" %d. %s = %s <== The re-entry point in the loop\n"),
+ i,
+ cmd_list.items[i - 1].string,
+ cmd_list.items[i].string);
+ else
+ /*
+ * TRANSLATORS: This is a
+ * single item in the list
+ * printed out by the "alias
+ * loop" message below.
+ */
+ strbuf_addf(&sb, _(" %d. %s = %s\n"),
+ i,
+ cmd_list.items[i - 1].string,
+ cmd_list.items[i].string);
+ }
+ /*
+ * TRANSLATORS: This is the last item in the
+ * list printed out by the "alias loop"
+ * message below.
+ */
+ strbuf_addf(&sb, _(" %d. %s = %s <== This is where the loop started!"),
+ i,
+ cmd_list.items[i - 1].string,
+ *argv[0]);
+ /*
+ * TRANSLATORS: The %s here at the end is
+ * going to be a list of aliases as formatted
+ * by the messages whose comments mention
+ * "alias loop" above.
+ */
+ die(_("alias loop: When expanding the alias '%s' we ran into a loop:\n%s"),
+ cmd_list.items[0].string, sb.buf);
+ }
string_list_append(&cmd_list, *argv[0]);
Now we'll print errors like:
$ ./git --exec-path=$PWD a
fatal: alias loop: When expanding the alias 'a' we ran into a loop:
1. a = b
2. b = c
3. c = d <== The re-entry point in the loop
4. d = e
5. e = c <== This is where the loop started!
Or, in the much simpler case of foo = bar; bar = foo:
$ ./git --exec-path=$PWD foo
fatal: alias loop: When expanding the alias 'foo' we ran into a loop:
1. foo = bar <== The re-entry point in the loop
2. bar = foo <== This is where the loop started!
I haven't tested this much, so maybe there's some edge cases I haven't
thought of / bugs in this reporting code, but hey, that's what the tests
I suggested are for :)
It's a lot more verbose, but I think it's worth it to produce better
error messages.
