[PATCH for-5.2 4/4] qemu-option: warn for short-form boolean options

[Paolo Bonzini <pbonzini@redhat.com>]

Options such as "server" or "nowait", that are commonly found in -chardev,
are sugar for "server=on" and "wait=off".  This is quite surprising and
also does not have any notion of typing attached.  It is even possible to
do "-device e1000,noid" and get a device with "id=off".

Deprecate all this, except for -chardev and -spice where it is in
wide use.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 chardev/char.c             |  1 +
 docs/system/deprecated.rst |  7 +++++++
 include/qemu/option.h      |  1 +
 tests/test-qemu-opts.c     |  1 +
 ui/spice-core.c            |  1 +
 util/qemu-option.c         | 22 +++++++++++++++-------
 6 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/chardev/char.c b/chardev/char.c
index 78553125d3..108da615df 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -829,6 +829,7 @@ Chardev *qemu_chr_find(const char *name)
 
 QemuOptsList qemu_chardev_opts = {
     .name = "chardev",
+    .allow_flag_options = true, /* server, nowait, etc. */
     .implied_opt_name = "backend",
     .head = QTAILQ_HEAD_INITIALIZER(qemu_chardev_opts.head),
     .desc = {
diff --git a/docs/system/deprecated.rst b/docs/system/deprecated.rst
index 32a0e620db..0e7edf7e56 100644
--- a/docs/system/deprecated.rst
+++ b/docs/system/deprecated.rst
@@ -146,6 +146,13 @@ Drives with interface types other than ``if=none`` are for onboard
 devices.  It is possible to use drives the board doesn't pick up with
 -device.  This usage is now deprecated.  Use ``if=none`` instead.
 
+Short-form boolean options (since 5.2)
+''''''''''''''''''''''''''''''''''''''
+
+Boolean options such as ``share=on``/``share=off`` can be written
+in short form as ``share`` and ``noshare``.  This is deprecated
+for all command-line options except ``-chardev` and ``-spice``, for
+which the short form was in wide use.
 
 QEMU Machine Protocol (QMP) commands
 ------------------------------------
diff --git a/include/qemu/option.h b/include/qemu/option.h
index ac69352e0e..046ac06a1f 100644
--- a/include/qemu/option.h
+++ b/include/qemu/option.h
@@ -65,6 +65,7 @@ struct QemuOptsList {
     const char *name;
     const char *implied_opt_name;
     bool merge_lists;  /* Merge multiple uses of option into a single list? */
+    bool allow_flag_options; /* Whether to warn for short-form boolean options */
     QTAILQ_HEAD(, QemuOpts) head;
     QemuOptDesc desc[];
 };
diff --git a/tests/test-qemu-opts.c b/tests/test-qemu-opts.c
index 297ffe79dd..a74c475773 100644
--- a/tests/test-qemu-opts.c
+++ b/tests/test-qemu-opts.c
@@ -77,6 +77,7 @@ static QemuOptsList opts_list_02 = {
 static QemuOptsList opts_list_03 = {
     .name = "opts_list_03",
     .implied_opt_name = "implied",
+    .allow_flag_options = true,
     .head = QTAILQ_HEAD_INITIALIZER(opts_list_03.head),
     .desc = {
         /* no elements => accept any params */
diff --git a/ui/spice-core.c b/ui/spice-core.c
index eea52f5389..08f834fa41 100644
--- a/ui/spice-core.c
+++ b/ui/spice-core.c
@@ -397,6 +397,7 @@ static SpiceChannelList *qmp_query_spice_channels(void)
 
 static QemuOptsList qemu_spice_opts = {
     .name = "spice",
+    .allow_flag_options = true, /* disable-agent-file-xfer, sasl, unix, etc. */
     .head = QTAILQ_HEAD_INITIALIZER(qemu_spice_opts.head),
     .merge_lists = true,
     .desc = {
diff --git a/util/qemu-option.c b/util/qemu-option.c
index 5824b7afe2..8b6050fbf7 100644
--- a/util/qemu-option.c
+++ b/util/qemu-option.c
@@ -779,16 +779,19 @@ void qemu_opts_print(QemuOpts *opts, const char *separator)
 
 static const char *get_opt_name_value(const char *params,
                                       const char *firstname,
+                                      bool warn_on_flag,
                                       bool *help_wanted,
                                       char **name, char **value)
 {
     const char *p;
+    const char *prefix = "";
     size_t len;
 
     len = strcspn(params, "=,");
     if (params[len] != '=') {
         if (help_wanted && starts_with_help_option(params) == len) {
             *help_wanted = true;
+            warn_on_flag = false;
         }
         /* found "foo,more" */
         if (firstname) {
@@ -801,9 +804,14 @@ static const char *get_opt_name_value(const char *params,
             if (strncmp(*name, "no", 2) == 0) {
                 memmove(*name, *name + 2, strlen(*name + 2) + 1);
                 *value = g_strdup("off");
+                prefix = "no";
             } else {
                 *value = g_strdup("on");
             }
+            if (warn_on_flag) {
+                error_report("short-form boolean option '%s%s' deprecated", prefix, *name);
+                error_printf("Please use %s=%s instead\n", *name, *value);
+            }
         }
     } else {
         /* found "foo=bar,more" */
@@ -822,14 +830,14 @@ static const char *get_opt_name_value(const char *params,
 
 static bool opts_do_parse(QemuOpts *opts, const char *params,
                           const char *firstname, bool prepend,
-                          bool *help_wanted, Error **errp)
+                          bool warn_on_flag, bool *help_wanted, Error **errp)
 {
     char *option, *value;
     const char *p;
     QemuOpt *opt;
 
     for (p = params; *p;) {
-        p = get_opt_name_value(p, firstname, help_wanted, &option, &value);
+        p = get_opt_name_value(p, firstname, warn_on_flag, help_wanted, &option, &value);
         if (help_wanted && *help_wanted) {
             return false;
         }
@@ -858,7 +866,7 @@ static char *opts_parse_id(const char *params)
     char *name, *value;
 
     for (p = params; *p;) {
-        p = get_opt_name_value(p, NULL, NULL, &name, &value);
+        p = get_opt_name_value(p, NULL, false, NULL, &name, &value);
         if (!strcmp(name, "id")) {
             g_free(name);
             return value;
@@ -877,7 +885,7 @@ bool has_help_option(const char *params)
     bool ret = false;
 
     for (p = params; *p;) {
-        p = get_opt_name_value(p, NULL, &ret, &name, &value);
+        p = get_opt_name_value(p, NULL, false, &ret, &name, &value);
         g_free(name);
         g_free(value);
         if (ret) {
@@ -897,7 +905,7 @@ bool has_help_option(const char *params)
 bool qemu_opts_do_parse(QemuOpts *opts, const char *params,
                        const char *firstname, Error **errp)
 {
-    return opts_do_parse(opts, params, firstname, false, NULL, errp);
+    return opts_do_parse(opts, params, firstname, false, false, NULL, errp);
 }
 
 static QemuOpts *opts_parse(QemuOptsList *list, const char *params,
@@ -925,8 +933,8 @@ static QemuOpts *opts_parse(QemuOptsList *list, const char *params,
         return NULL;
     }
 
-    if (!opts_do_parse(opts, params, firstname, defaults, help_wanted,
-                       errp)) {
+    if (!opts_do_parse(opts, params, firstname, defaults,
+                       !list->allow_flag_options, help_wanted, errp)) {
         qemu_opts_del(opts);
         return NULL;
     }
-- 
2.26.2