Re: [PATCH v4 2/5] ref-filter: add return value && strbuf to handlers

[Eric Sunshine]

On Tue, Mar 20, 2018 at 12:05 PM, Olga Telezhnaya
 wrote:
> Continue removing die() calls from ref-filter formatting logic,
> so that it could be used by other commands.
> [...]
> Signed-off-by: Olga Telezhnaia 
> ---
> diff --git a/ref-filter.c b/ref-filter.c
> @@ -596,19 +603,24 @@ static int is_empty(const char *s)
> +static int then_atom_handler(struct atom_value *atomv, struct 
> ref_formatting_state *state,
> +struct strbuf *err)
>  {
> struct ref_formatting_stack *cur = state->stack;
> struct if_then_else *if_then_else = NULL;
>
> if (cur->at_end == if_then_else_handler)
> if_then_else = (struct if_then_else *)cur->at_end_data;
> -   if (!if_then_else)
> -   die(_("format: %%(then) atom used without an %%(if) atom"));
> -   if (if_then_else->then_atom_seen)
> -   die(_("format: %%(then) atom used more than once"));
> -   if (if_then_else->else_atom_seen)
> -   die(_("format: %%(then) atom used after %%(else)"));
> +   if (!if_then_else) {
> +   strbuf_addstr(err, _("format: %(then) atom used without an 
> %(if) atom"));
> +   return -1;
> +   } else if (if_then_else->then_atom_seen) {
> +   strbuf_addstr(err, _("format: %(then) atom used more than 
> once"));
> +   return -1;
> +   } else if (if_then_else->else_atom_seen) {
> +   strbuf_addstr(err, _("format: %(then) atom used after 
> %(else)"));
> +   return -1;
> +   }

This pattern of transforming:

if (cond)
die("...");

to:

if (cond) {
strbuf_add*(...);
return -1;
}

is repeated many, many times throughout this patch series and makes
for quite noisy diffs. Such repetition and noise suggests that this
patch series (and other similar ones) could benefit from a convenience
function similar to the existing error() function. For instance:

int strbuf_error(struct strbuf *buf, const char *fmt, ...);

which appends the formatted message to 'buf' and unconditionally
returns -1. Thus, the above transformation simplifies to:

if (cond)
return strbuf_error(, "...", ...);

which makes for a much less noisy diff, thus is easier to review.

A new patch introducing such a function at the head of this patch
series might be welcome.

[PATCH v4 2/5] ref-filter: add return value && strbuf to handlers

[Olga Telezhnaya]

Continue removing die() calls from ref-filter formatting logic,
so that it could be used by other commands.

Change the signature of handlers by adding return value
and strbuf parameter for errors.
Return value equals 0 upon success and -1 upon failure (there could be
more error codes further if necessary). Upon failure, error message is
appended to the strbuf.

Signed-off-by: Olga Telezhnaia 
---
 ref-filter.c | 71 
 1 file changed, 48 insertions(+), 23 deletions(-)

diff --git a/ref-filter.c b/ref-filter.c
index 54fae00bdd410..d120360104806 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -387,7 +387,8 @@ struct ref_formatting_state {
 
 struct atom_value {
const char *s;
-   void (*handler)(struct atom_value *atomv, struct ref_formatting_state 
*state);
+   int (*handler)(struct atom_value *atomv, struct ref_formatting_state 
*state,
+  struct strbuf *err);
uintmax_t value; /* used for sorting when not FIELD_STR */
struct used_atom *atom;
 };
@@ -481,7 +482,8 @@ static void quote_formatting(struct strbuf *s, const char 
*str, int quote_style)
}
 }
 
-static void append_atom(struct atom_value *v, struct ref_formatting_state 
*state)
+static int append_atom(struct atom_value *v, struct ref_formatting_state 
*state,
+  struct strbuf *unused_err)
 {
/*
 * Quote formatting is only done when the stack has a single
@@ -493,6 +495,7 @@ static void append_atom(struct atom_value *v, struct 
ref_formatting_state *state
quote_formatting(>stack->output, v->s, 
state->quote_style);
else
strbuf_addstr(>stack->output, v->s);
+   return 0;
 }
 
 static void push_stack_element(struct ref_formatting_stack **stack)
@@ -527,7 +530,8 @@ static void end_align_handler(struct ref_formatting_stack 
**stack)
strbuf_release();
 }
 
-static void align_atom_handler(struct atom_value *atomv, struct 
ref_formatting_state *state)
+static int align_atom_handler(struct atom_value *atomv, struct 
ref_formatting_state *state,
+ struct strbuf *unused_err)
 {
struct ref_formatting_stack *new_stack;
 
@@ -535,6 +539,7 @@ static void align_atom_handler(struct atom_value *atomv, 
struct ref_formatting_s
new_stack = state->stack;
new_stack->at_end = end_align_handler;
new_stack->at_end_data = >atom->u.align;
+   return 0;
 }
 
 static void if_then_else_handler(struct ref_formatting_stack **stack)
@@ -572,7 +577,8 @@ static void if_then_else_handler(struct 
ref_formatting_stack **stack)
free(if_then_else);
 }
 
-static void if_atom_handler(struct atom_value *atomv, struct 
ref_formatting_state *state)
+static int if_atom_handler(struct atom_value *atomv, struct 
ref_formatting_state *state,
+  struct strbuf *unused_err)
 {
struct ref_formatting_stack *new_stack;
struct if_then_else *if_then_else = xcalloc(sizeof(struct 
if_then_else), 1);
@@ -584,6 +590,7 @@ static void if_atom_handler(struct atom_value *atomv, 
struct ref_formatting_stat
new_stack = state->stack;
new_stack->at_end = if_then_else_handler;
new_stack->at_end_data = if_then_else;
+   return 0;
 }
 
 static int is_empty(const char *s)
@@ -596,19 +603,24 @@ static int is_empty(const char *s)
return 1;
 }
 
-static void then_atom_handler(struct atom_value *atomv, struct 
ref_formatting_state *state)
+static int then_atom_handler(struct atom_value *atomv, struct 
ref_formatting_state *state,
+struct strbuf *err)
 {
struct ref_formatting_stack *cur = state->stack;
struct if_then_else *if_then_else = NULL;
 
if (cur->at_end == if_then_else_handler)
if_then_else = (struct if_then_else *)cur->at_end_data;
-   if (!if_then_else)
-   die(_("format: %%(then) atom used without an %%(if) atom"));
-   if (if_then_else->then_atom_seen)
-   die(_("format: %%(then) atom used more than once"));
-   if (if_then_else->else_atom_seen)
-   die(_("format: %%(then) atom used after %%(else)"));
+   if (!if_then_else) {
+   strbuf_addstr(err, _("format: %(then) atom used without an 
%(if) atom"));
+   return -1;
+   } else if (if_then_else->then_atom_seen) {
+   strbuf_addstr(err, _("format: %(then) atom used more than 
once"));
+   return -1;
+   } else if (if_then_else->else_atom_seen) {
+   strbuf_addstr(err, _("format: %(then) atom used after 
%(else)"));
+   return -1;
+   }
if_then_else->then_atom_seen = 1;
/*
 * If the 'equals' or 'notequals' attribute is used then
@@ -624,34 +636,44 @@ static void then_atom_handler(struct atom_value *atomv, 
struct ref_formatting_st
} else if (cur->output.len