Do basic error checking in ref_transaction_create() and make it return
non-zero on error. Update all callers to check the result of
ref_transaction_create(). There are currently no conditions in _create that
will return error but there will be in the future. Add an err argument that
will be updated on failure.
Reviewed-by: Jonathan Nieder <jrnieder@xxxxxxxxx>
Signed-off-by: Ronnie Sahlberg <sahlberg@xxxxxxxxxx>
---
builtin/update-ref.c | 4 +++-
refs.c | 18 +++++++++++------
refs.h | 55 +++++++++++++++++++++++++++++++++++++++++++++-------
3 files changed, 63 insertions(+), 14 deletions(-)
diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 3067b11..41121fa 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -226,7 +226,9 @@ static const char *parse_cmd_create(struct strbuf *input, const char *next)
if (*next != line_termination)
die("create %s: extra input: %s", refname, next);
- ref_transaction_create(transaction, refname, new_sha1, update_flags);
+ if (ref_transaction_create(transaction, refname, new_sha1,
+ update_flags, &err))
+ die("%s", err.buf);
update_flags = 0;
free(refname);
diff --git a/refs.c b/refs.c
index 88d2df4..78ae4f0 100644
--- a/refs.c
+++ b/refs.c
@@ -3472,18 +3472,24 @@ int ref_transaction_update(struct ref_transaction *transaction,
return 0;
}
-void ref_transaction_create(struct ref_transaction *transaction,
- const char *refname,
- const unsigned char *new_sha1,
- int flags)
+int ref_transaction_create(struct ref_transaction *transaction,
+ const char *refname,
+ const unsigned char *new_sha1,
+ int flags,
+ struct strbuf *err)
{
- struct ref_update *update = add_update(transaction, refname);
+ struct ref_update *update;
+
+ if (!new_sha1 || is_null_sha1(new_sha1))
+ die("BUG: create ref with null new_sha1");
+
+ update = add_update(transaction, refname);
- assert(!is_null_sha1(new_sha1));
hashcpy(update->new_sha1, new_sha1);
hashclr(update->old_sha1);
update->flags = flags;
update->have_old = 1;
+ return 0;
}
void ref_transaction_delete(struct ref_transaction *transaction,
diff --git a/refs.h b/refs.h
index 6c99ccf..d1ba4e8 100644
--- a/refs.h
+++ b/refs.h
@@ -10,6 +10,45 @@ struct ref_lock {
int force_write;
};
+/*
+ * A ref_transaction represents a collection of ref updates
+ * that should succeed or fail together.
+ *
+ * Calling sequence
+ * ----------------
+ * - Allocate and initialize a `struct ref_transaction` by calling
+ * `ref_transaction_begin()`.
+ *
+ * - List intended ref updates by calling functions like
+ * `ref_transaction_update()` and `ref_transaction_create()`.
+ *
+ * - Call `ref_transaction_commit()` to execute the transaction.
+ * If this succeeds, the ref updates will have taken place and
+ * the transaction cannot be rolled back.
+ *
+ * - At any time call `ref_transaction_free()` to discard the
+ * transaction and free associated resources. In particular,
+ * this rolls back the transaction if it has not been
+ * successfully committed.
+ *
+ * Error handling
+ * --------------
+ *
+ * On error, transaction functions append a message about what
+ * went wrong to the 'err' argument. The message mentions what
+ * ref was being updated (if any) when the error occurred so it
+ * can be passed to 'die' or 'error' as-is.
+ *
+ * The message is appended to err without first clearing err.
+ * This allows the caller to prepare preamble text to the generated
+ * error message:
+ *
+ * strbuf_addf(&err, "Error while doing foo-bar: ");
+ * if (ref_transaction_update(..., &err)) {
+ * ret = error("%s", err.buf);
+ * goto cleanup;
+ * }
+ */
struct ref_transaction;
/*
@@ -248,7 +287,7 @@ struct ref_transaction *ref_transaction_begin(void);
* it must not have existed beforehand.
* Function returns 0 on success and non-zero on failure. A failure to update
* means that the transaction as a whole has failed and will need to be
- * rolled back. On failure the err buffer will be updated.
+ * rolled back.
*/
int ref_transaction_update(struct ref_transaction *transaction,
const char *refname,
@@ -262,11 +301,15 @@ int ref_transaction_update(struct ref_transaction *transaction,
* that the reference should have after the update; it must not be the
* null SHA-1. It is verified that the reference does not exist
* already.
+ * Function returns 0 on success and non-zero on failure. A failure to create
+ * means that the transaction as a whole has failed and will need to be
+ * rolled back.
*/
-void ref_transaction_create(struct ref_transaction *transaction,
- const char *refname,
- const unsigned char *new_sha1,
- int flags);
+int ref_transaction_create(struct ref_transaction *transaction,
+ const char *refname,
+ const unsigned char *new_sha1,
+ int flags,
+ struct strbuf *err);
/*
* Add a reference deletion to transaction. If have_old is true, then
@@ -282,8 +325,6 @@ void ref_transaction_delete(struct ref_transaction *transaction,
* Commit all of the changes that have been queued in transaction, as
* atomically as possible. Return a nonzero value if there is a
* problem.
- * If err is non-NULL we will add an error string to it to explain why
- * the transaction failed. The string does not end in newline.
*/
int ref_transaction_commit(struct ref_transaction *transaction,
const char *msg, struct strbuf *err);
--
2.0.0.438.gec92e5c
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