Make "directory" setting work with extension_control_path

The extension_control_path setting (commit 4f7f7b03758) did not
support extensions that set a custom "directory" setting in their
control file.  Very few extensions use that and during the discussion
on the previous commit it was suggested to maybe remove that
functionality.  But a fix was easier than initially thought, so this
just adds that support.  The fix is to use the control->control_dir as
a share dir to return the path of the extension script files.

To make this work more sensibly overall, the directory suffix
"extension" is no longer to be included in the extension_control_path
value.  To quote the patch, it would be

-extension_control_path = '/usr/local/share/postgresql/extension:/home/my_project/share/extension:$system'
+extension_control_path = '/usr/local/share/postgresql:/home/my_project/share:$system'

During the initial patch, there was some discussion on which of these
two approaches would be better, and the committed patch was a 50/50
decision.  But the support for the "directory" setting pushed it the
other way, and also it seems like many people didn't like the previous
behavior much.

Author: Matheus Alcantara <[email protected]>
Reviewed-by: Christoph Berg <[email protected]>
Reviewed-by: David E. Wheeler <[email protected]>
Discussion: https://www.postgresql.org/message-id/flat/aAi1VACxhjMhjFnb%40msg.df7cb.de#0cdf7b7d727cc593b029650daa3c4fbc

1 files changed, 69 insertions, 26 deletions

diff --git a/src/backend/commands/extension.c b/src/backend/commands/extension.c
index 180f4af9be3..73c52e970f6 100644
--- a/src/backend/commands/extension.c
+++ b/src/backend/commands/extension.c
@@ -83,6 +83,8 @@ Oid			CurrentExtensionObject = InvalidOid;
 typedef struct ExtensionControlFile
 {
 	char	   *name;			/* name of the extension */
+	char	   *basedir;		/* base directory where control and script
+								 * files are located */
 	char	   *control_dir;	/* directory where control file was found */
 	char	   *directory;		/* directory for script files */
 	char	   *default_version;	/* default install target version, if any */
@@ -153,6 +155,7 @@ static void ExecAlterExtensionContentsRecurse(AlterExtensionContentsStmt *stmt,
 static char *read_whole_file(const char *filename, int *length);
 static ExtensionControlFile *new_ExtensionControlFile(const char *extname);
 
+char	   *find_in_paths(const char *basename, List *paths);
 
 /*
  * get_extension_oid - given an extension name, look up the OID
@@ -374,8 +377,15 @@ get_extension_control_directories(void)
 			piece = palloc(len + 1);
 			strlcpy(piece, ecp, len + 1);
 
-			/* Substitute the path macro if needed */
-			mangled = substitute_path_macro(piece, "$system", system_dir);
+			/*
+			 * Substitute the path macro if needed or append "extension"
+			 * suffix if it is a custom extension control path.
+			 */
+			if (strcmp(piece, "$system") == 0)
+				mangled = substitute_path_macro(piece, "$system", system_dir);
+			else
+				mangled = psprintf("%s/extension", piece);
+
 			pfree(piece);
 
 			/* Canonicalize the path based on the OS and add to the list */
@@ -401,28 +411,16 @@ get_extension_control_directories(void)
 static char *
 find_extension_control_filename(ExtensionControlFile *control)
 {
-	char		sharepath[MAXPGPATH];
-	char	   *system_dir;
 	char	   *basename;
-	char	   *ecp;
 	char	   *result;
+	List	   *paths;
 
 	Assert(control->name);
 
-	get_share_path(my_exec_path, sharepath);
-	system_dir = psprintf("%s/extension", sharepath);
-
 	basename = psprintf("%s.control", control->name);
 
-	/*
-	 * find_in_path() does nothing if the path value is empty.  This is the
-	 * historical behavior for dynamic_library_path, but it makes no sense for
-	 * extensions.  So in that case, substitute a default value.
-	 */
-	ecp = Extension_control_path;
-	if (strlen(ecp) == 0)
-		ecp = "$system";
-	result = find_in_path(basename, ecp, "extension_control_path", "$system", system_dir);
+	paths = get_extension_control_directories();
+	result = find_in_paths(basename, paths);
 
 	if (result)
 	{
@@ -439,12 +437,11 @@ find_extension_control_filename(ExtensionControlFile *control)
 static char *
 get_extension_script_directory(ExtensionControlFile *control)
 {
-	char		sharepath[MAXPGPATH];
-	char	   *result;
-
 	/*
 	 * The directory parameter can be omitted, absolute, or relative to the
-	 * installation's share directory.
+	 * installation's base directory, which can be the sharedir or a custom
+	 * path that it was set extension_control_path. It depends where the
+	 * .control file was found.
 	 */
 	if (!control->directory)
 		return pstrdup(control->control_dir);
@@ -452,11 +449,8 @@ get_extension_script_directory(ExtensionControlFile *control)
 	if (is_absolute_path(control->directory))
 		return pstrdup(control->directory);
 
-	get_share_path(my_exec_path, sharepath);
-	result = (char *) palloc(MAXPGPATH);
-	snprintf(result, MAXPGPATH, "%s/%s", sharepath, control->directory);
-
-	return result;
+	Assert(control->basedir != NULL);
+	return psprintf("%s/%s", control->basedir, control->directory);
 }
 
 static char *
@@ -550,6 +544,14 @@ parse_extension_control_file(ExtensionControlFile *control,
 				 errhint("The extension must first be installed on the system where PostgreSQL is running.")));
 	}
 
+	/* Assert that the control_dir ends with /extension */
+	Assert(control->control_dir != NULL);
+	Assert(strcmp(control->control_dir + strlen(control->control_dir) - strlen("/extension"), "/extension") == 0);
+
+	control->basedir = pnstrdup(
+								control->control_dir,
+								strlen(control->control_dir) - strlen("/extension"));
+
 	if ((file = AllocateFile(filename, "r")) == NULL)
 	{
 		/* no complaint for missing auxiliary file */
@@ -3863,3 +3865,44 @@ new_ExtensionControlFile(const char *extname)
 
 	return control;
 }
+
+/*
+ * Work in a very similar way with find_in_path but it receives an already
+ * parsed List of paths to search the basename and it do not support macro
+ * replacement or custom error messages (for simplicity).
+ *
+ * By "already parsed List of paths" this function expected that paths already
+ * have all macros replaced.
+ */
+char *
+find_in_paths(const char *basename, List *paths)
+{
+	ListCell   *cell;
+
+	foreach(cell, paths)
+	{
+		char	   *path = lfirst(cell);
+		char	   *full;
+
+		Assert(path != NULL);
+
+		path = pstrdup(path);
+		canonicalize_path(path);
+
+		/* only absolute paths */
+		if (!is_absolute_path(path))
+			ereport(ERROR,
+					errcode(ERRCODE_INVALID_NAME),
+					errmsg("component in parameter \"%s\" is not an absolute path", "extension_control_path"));
+
+		full = psprintf("%s/%s", path, basename);
+
+		if (pg_file_exists(full))
+			return full;
+
+		pfree(path);
+		pfree(full);
+	}
+
+	return NULL;
+}