provider: Major refactor

- Providers for features are now registered as a unit. For example, instead of
  calling `register_provider("clipboard_get")` and
  `register_provider("clipboard_set")`, clients call
  `register_provider("clipboard")` and nvim will assume it implements all
  methods of the "clipboard" feature
- Bootstrapping code was removed. With the `api_spawn` function exposed to
  vimscript, it's no longer necessary and will be handled by plugins
  distributed with nvim.
- Now the `has` function will return true if there's a live channel that
  has registered as a provider for the feature.
- 'initpython'/'initclipboard' options were removed
- A new API function was exposed: `vim_discover_features` which returns an
  object with information about pluggable features such as 'python' or
  'clipboard'

4 files changed, 66 insertions, 126 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index b1d5a067b4..e14c427dc1 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -502,22 +502,28 @@ void vim_unsubscribe(uint64_t channel_id, String event)
   channel_unsubscribe(channel_id, e);
 }
 
-/// Registers the channel as the provider for `method`. This fails if
-/// a provider for `method` is already registered.
+/// Registers the channel as the provider for `feature`. This fails if
+/// a provider for `feature` is already provided by another channel.
 ///
 /// @param channel_id The channel id
-/// @param method The method name
+/// @param feature The feature name
 /// @param[out] err Details of an error that may have occurred
-void vim_register_provider(uint64_t channel_id, String method, Error *err)
+void vim_register_provider(uint64_t channel_id, String feature, Error *err)
 {
   char buf[METHOD_MAXLEN];
-  xstrlcpy(buf, method.data, sizeof(buf));
+  xstrlcpy(buf, feature.data, sizeof(buf));
 
   if (!provider_register(buf, channel_id)) {
-    set_api_error("Provider already registered", err);
+    set_api_error("Feature doesn't exist", err);
   }
 }
 
+/// Returns a feature->method list dictionary for all pluggable features
+Dictionary vim_discover_features(void)
+{
+  return provider_get_all();
+}
+
 /// Writes a message to vim output or error buffer. The string is split
 /// and flushed after each newline. Incomplete lines are kept for writing
 /// later.
diff --git a/src/nvim/option.c b/src/nvim/option.c
index b9becebbf4..b26b6ed4cc 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -974,12 +974,6 @@ static struct vimoption
   {"infercase",   "inf",  P_BOOL|P_VI_DEF,
    (char_u *)&p_inf, PV_INF,
    {(char_u *)FALSE, (char_u *)0L} SCRIPTID_INIT},
-  {"initclipboard","icpb",P_STRING|P_VI_DEF|P_SECURE,
-   (char_u *)&p_icpb, PV_NONE,
-   {(char_u *)"", (char_u *)0L} SCRIPTID_INIT},
-  {"initpython","ipy",P_STRING|P_VI_DEF|P_SECURE,
-   (char_u *)&p_ipy, PV_NONE,
-   {(char_u *)"", (char_u *)0L} SCRIPTID_INIT},
   {"insertmode",  "im",   P_BOOL|P_VI_DEF|P_VIM,
    (char_u *)&p_im, PV_NONE,
    {(char_u *)FALSE, (char_u *)0L} SCRIPTID_INIT},
diff --git a/src/nvim/option_defs.h b/src/nvim/option_defs.h
index 555e9166d6..cd61b6427c 100644
--- a/src/nvim/option_defs.h
+++ b/src/nvim/option_defs.h
@@ -631,8 +631,6 @@ EXTERN int p_write;             /* 'write' */
 EXTERN int p_wa;                /* 'writeany' */
 EXTERN int p_wb;                /* 'writebackup' */
 EXTERN long p_wd;               /* 'writedelay' */
-EXTERN char *p_ipy;             // 'initpython'
-EXTERN char *p_icpb;            // 'initclipboard'
 
 /*
  * "indir" values for buffer-local opions.
diff --git a/src/nvim/os/provider.c b/src/nvim/os/provider.c
index 57c2e57a3c..e56e33aa1a 100644
--- a/src/nvim/os/provider.c
+++ b/src/nvim/os/provider.c
@@ -17,33 +17,31 @@
 
 #define FEATURE_COUNT (sizeof(features) / sizeof(features[0]))
 
-#define FEATURE(feature_name, provider_bootstrap_command, ...) {            \
+#define FEATURE(feature_name, ...) {            \
   .name = feature_name,                                                     \
-  .bootstrap_command = provider_bootstrap_command,                          \
-  .argv = NULL,                                                             \
   .channel_id = 0,                                                          \
   .methods = (char *[]){__VA_ARGS__, NULL}                                  \
 }
 
-static struct feature {
-  char *name, **bootstrap_command, **argv, **methods;
+typedef struct {
+  char *name, **methods;
   size_t name_length;
   uint64_t channel_id;
-} features[] = {
+} Feature;
+
+static Feature features[] = {
   FEATURE("python",
-          &p_ipy,
           "python_execute",
           "python_execute_file",
           "python_do_range",
           "python_eval"),
 
   FEATURE("clipboard",
-          &p_icpb,
           "clipboard_get",
           "clipboard_set")
 };
 
-static Map(cstr_t, uint64_t) *registered_providers = NULL;
+static PMap(cstr_t) *registered_providers = NULL;
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS
 # include "os/provider.c.generated.h"
@@ -52,60 +50,57 @@ static Map(cstr_t, uint64_t) *registered_providers = NULL;
 
 void provider_init(void)
 {
-  registered_providers = map_new(cstr_t, uint64_t)();
+  registered_providers = pmap_new(cstr_t)();
 }
 
 bool provider_has_feature(char *name)
 {
-  for (size_t i = 0; i < FEATURE_COUNT; i++) {
-    struct feature *f = &features[i];
-    if (!STRICMP(name, f->name)) {
-      return f->channel_id || can_execute(f);
-    }
-  }
-
-  return false;
+  Feature *f = find_feature(name);
+  return f != NULL && channel_exists(f->channel_id);
 }
 
-bool provider_available(char *method)
+bool provider_register(char *name, uint64_t channel_id)
 {
-  return map_has(cstr_t, uint64_t)(registered_providers, method);
-}
+  Feature *f = find_feature(name);
 
-bool provider_register(char *method, uint64_t channel_id)
-{
-  if (map_has(cstr_t, uint64_t)(registered_providers, method)) {
+  if (!f) {
     return false;
   }
 
-  // First check if this method is part of a feature, and if so, update
-  // the feature structure with the channel id
-  struct feature *f = get_feature_for(method);
-  if (f) {
-    DLOG("Registering provider for \"%s\" "
-        "which is part of the \"%s\" feature",
-        method,
-        f->name);
-    f->channel_id = channel_id;
+  if (f->channel_id && channel_exists(f->channel_id)) {
+    ILOG("Feature \"%s\" is already provided by another channel"
+         "(will be replaced)", name);
+  }
+
+  DLOG("Registering provider for \"%s\"", name);
+  f->channel_id = channel_id;
+
+  // Associate all method names with the feature struct
+  size_t i;
+  char *method;
+  for (method = f->methods[i = 0]; method; method = f->methods[++i]) {
+    pmap_put(cstr_t)(registered_providers, method, f);
+    DLOG("Channel \"%" PRIu64 "\" will be sent requests for \"%s\"",
+         channel_id,
+         method);
   }
 
-  map_put(cstr_t, uint64_t)(registered_providers, xstrdup(method), channel_id);
-  ILOG("Registered channel %" PRIu64 " as the provider for \"%s\"",
+  ILOG("Registered channel %" PRIu64 " as the provider for the \"%s\" feature",
        channel_id,
-       method);
+       name);
 
   return true;
 }
 
 Object provider_call(char *method, Array args)
 {
-  uint64_t channel_id = get_provider_for(method);
+  Feature *f = pmap_get(cstr_t)(registered_providers, method);
 
-  if (!channel_id) {
+  if (!f || !channel_exists(f->channel_id)) {
     char buf[256];
     snprintf(buf,
              sizeof(buf),
-             "Provider for \"%s\" is not available",
+             "Provider for method \"%s\" is not available",
              method);
     report_error(buf);
     api_free_array(args);
@@ -114,7 +109,7 @@ Object provider_call(char *method, Array args)
 
   bool error = false;
   Object result = NIL;
-  channel_send_call(channel_id, method, args, &result, &error);
+  channel_send_call(f->channel_id, method, args, &result, &error);
 
   if (error) {
     report_error(result.data.string.data);
@@ -125,62 +120,36 @@ Object provider_call(char *method, Array args)
   return result;
 }
 
-static uint64_t get_provider_for(char *method)
+Dictionary provider_get_all(void)
 {
-  uint64_t channel_id = map_get(cstr_t, uint64_t)(registered_providers, method);
-
-  if (channel_id) {
-    return channel_id;
-  }
-
-  // Try to bootstrap if the method is part of a feature
-  struct feature *f = get_feature_for(method);
-
-  if (!f || !can_execute(f)) {
-    ELOG("Cannot bootstrap provider for \"%s\"", method);
-    goto err;
-  }
+  Dictionary rv = ARRAY_DICT_INIT;
 
-  if (f->channel_id) {
-    ELOG("Already bootstrapped provider for \"%s\"", f->name);
-    goto err;
-  }
+  for (size_t i = 0; i < FEATURE_COUNT; i++) {
+    Array methods = ARRAY_DICT_INIT;
+    Feature *f = &features[i];
 
-  f->channel_id = channel_from_job(f->argv);
+    size_t j;
+    char *method;
+    for (method = f->methods[j = 0]; method; method = f->methods[++j]) {
+      ADD(methods, STRING_OBJ(cstr_to_string(method)));
+    }
 
-  if (!f->channel_id) {
-    ELOG("The provider for \"%s\" failed to bootstrap", f->name);
-    goto err;
+    PUT(rv, f->name, ARRAY_OBJ(methods));
   }
 
-  return f->channel_id;
-
-err:
-  // Ensure we won't try to restart the provider
-  if (f) {
-    f->bootstrap_command = NULL;
-    f->channel_id = 0;
-  }
-  return 0;
+  return rv;
 }
 
-static bool can_execute(struct feature *f)
+static Feature * find_feature(char *name)
 {
-  if (!f->bootstrap_command) {
-    return false;
-  }
-
-  char *cmd = *f->bootstrap_command;
-
-  if (!cmd || !strlen(cmd)) {
-    return false;
-  }
-
-  if (!f->argv) {
-    f->argv = shell_build_argv((uint8_t *)cmd, NULL);
+  for (size_t i = 0; i < FEATURE_COUNT; i++) {
+    Feature *f = &features[i];
+    if (!STRICMP(name, f->name)) {
+      return f;
+    }
   }
 
-  return os_can_exe((uint8_t *)f->argv[0]);
+  return NULL;
 }
 
 static void report_error(char *str)
@@ -188,30 +157,3 @@ static void report_error(char *str)
   vim_err_write((String) {.data = str, .size = strlen(str)});
   vim_err_write((String) {.data = "\n", .size = 1});
 }
-
-static bool feature_has_method(struct feature *f, char *method)
-{
-  size_t i;
-  char *m;
-
-  for (m = f->methods[i = 0]; m; m = f->methods[++i]) {
-    if (!STRCMP(method, m)) {
-      return true;
-    }
-  }
-
-  return false;
-}
-
-
-static struct feature *get_feature_for(char *method)
-{
-  for (size_t i = 0; i < FEATURE_COUNT; i++) {
-    struct feature *f = &features[i];
-    if (feature_has_method(f, method)) {
-      return f;
-    }
-  }
-
-  return NULL;
-}