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+From: Austin Clements <amdragon@MIT.EDU>\r
+To: notmuch@notmuchmail.org\r
+Subject: [PATCH 1/7] cli: Framework for structured output versioning\r
+Date: Sat, 15 Dec 2012 22:17:23 -0500\r
+Message-Id: <1355627849-29099-2-git-send-email-amdragon@mit.edu>\r
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+References: <1355627849-29099-1-git-send-email-amdragon@mit.edu>\r
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+\r
+Currently there is a period of pain whenever we make\r
+backward-incompatible changes to the structured output format, which\r
+discourages not only backward-incompatible improvements to the format,\r
+but also backwards-compatible additions that may not be "perfect". In\r
+the end, these problems limit experimentation and innovation.\r
+\r
+This series of patches introduces a way for CLI callers to request a\r
+specific format version on the command line and to determine if the\r
+CLI does not supported the requested version (and perhaps present a\r
+useful diagnostic to the user). Since the caller requests a format\r
+version, it's also possible for the CLI to support multiple\r
+incompatible versions simultaneously, unlike the alternate approach of\r
+including version information in the output.\r
+\r
+This patch lays the groundwork by introducing a versioning convention,\r
+standard exit codes, and a utility function to check the requested\r
+version and produce standardized diagnostic messages and exit\r
+statuses.\r
+---\r
+ devel/schemata | 2 ++\r
+ notmuch-client.h | 45 +++++++++++++++++++++++++++++++++++++++++++++\r
+ notmuch.c | 32 ++++++++++++++++++++++++++++++++\r
+ 3 files changed, 79 insertions(+)\r
+\r
+diff --git a/devel/schemata b/devel/schemata\r
+index d1ab983..292f287 100644\r
+--- a/devel/schemata\r
++++ b/devel/schemata\r
+@@ -14,6 +14,8 @@ are interleaved. Keys are printed as keywords (symbols preceded by a\r
+ colon), e.g. (:id "123" :time 54321 :from "foobar"). Null is printed as\r
+ nil, true as t and false as nil.\r
+ \r
++This is version 1 of the structured output format.\r
++\r
+ Common non-terminals\r
+ --------------------\r
+ \r
+diff --git a/notmuch-client.h b/notmuch-client.h\r
+index 1c336dc..d7b352e 100644\r
+--- a/notmuch-client.h\r
++++ b/notmuch-client.h\r
+@@ -117,6 +117,51 @@ chomp_newline (char *str)\r
+ str[strlen(str)-1] = '\0';\r
+ }\r
+ \r
++/* Exit status code indicating the requested format version is too old\r
++ * (support for that version has been dropped). CLI code should use\r
++ * notmuch_exit_if_unsupported_format rather than directly exiting\r
++ * with this code.\r
++ */\r
++#define NOTMUCH_EXIT_FORMAT_TOO_OLD 20\r
++/* Exit status code indicating the requested format version is newer\r
++ * than the version supported by the CLI. CLI code should use\r
++ * notmuch_exit_if_unsupported_format rather than directly exiting\r
++ * with this code.\r
++ */\r
++#define NOTMUCH_EXIT_FORMAT_TOO_NEW 21\r
++\r
++/* The current structured output format version. Requests for format\r
++ * versions above this will return an error. Backwards-incompatible\r
++ * changes such as removing map fields, changing the meaning of map\r
++ * fields, or changing the meanings of list elements should increase\r
++ * this. New (required) map fields can be added without increasing\r
++ * this.\r
++ */\r
++#define NOTMUCH_FORMAT_CUR 1\r
++/* The minimum supported structured output format version. Requests\r
++ * for format versions below this will return an error. */\r
++#define NOTMUCH_FORMAT_MIN 1\r
++\r
++/* The output format version requested by the caller on the command\r
++ * line. If no format version is requested, this will be set to\r
++ * NOTMUCH_FORMAT_CUR. Even though the command-line option is\r
++ * per-command, this is global because commands can share structured\r
++ * output code.\r
++ */\r
++extern int notmuch_format_version;\r
++\r
++/* Commands that support structured output should support the\r
++ * following argument\r
++ * { NOTMUCH_OPT_INT, ¬much_format_version, "format-version", 0, 0 }\r
++ * and should invoke notmuch_exit_if_unsupported_format to check the\r
++ * requested version. If notmuch_format_version is outside the\r
++ * supported range, this will print a detailed diagnostic message for\r
++ * the user and exit with NOTMUCH_EXIT_FORMAT_TOO_{OLD,NEW} to inform\r
++ * the invoking program of the problem.\r
++ */\r
++void\r
++notmuch_exit_if_unsupported_format (void);\r
++\r
+ notmuch_crypto_context_t *\r
+ notmuch_crypto_get_context (notmuch_crypto_t *crypto, const char *protocol);\r
+ \r
+diff --git a/notmuch.c b/notmuch.c\r
+index 4ff66e3..9516dfb 100644\r
+--- a/notmuch.c\r
++++ b/notmuch.c\r
+@@ -82,6 +82,8 @@ static command_t commands[] = {\r
+ "This message, or more detailed help for the named command." }\r
+ };\r
+ \r
++int notmuch_format_version;\r
++\r
+ static void\r
+ usage (FILE *out)\r
+ {\r
+@@ -109,6 +111,33 @@ usage (FILE *out)\r
+ "and \"notmuch help search-terms\" for the common search-terms syntax.\n\n");\r
+ }\r
+ \r
++void\r
++notmuch_exit_if_unsupported_format (void)\r
++{\r
++ if (notmuch_format_version > NOTMUCH_FORMAT_CUR) {\r
++ fprintf (stderr, "\\r
++A caller requested output format version %d, but the installed notmuch\n\\r
++CLI only supports up to format version %d. You may need to upgrade your\n\\r
++notmuch CLI.\n",\r
++ notmuch_format_version, NOTMUCH_FORMAT_CUR);\r
++ exit (NOTMUCH_EXIT_FORMAT_TOO_NEW);\r
++ } else if (notmuch_format_version < NOTMUCH_FORMAT_MIN) {\r
++ fprintf (stderr, "\\r
++A caller requested output format version %d, which is no longer supported\n\\r
++by the notmuch CLI (it requires at least version %d). You may need to\n\\r
++upgrade your notmuch front-end.\n",\r
++ notmuch_format_version, NOTMUCH_FORMAT_MIN);\r
++ exit (NOTMUCH_EXIT_FORMAT_TOO_OLD);\r
++ } else if (notmuch_format_version != NOTMUCH_FORMAT_CUR) {\r
++ /* Warn about old version requests so compatibility issues are\r
++ * less likely when we drop support for a deprecated format\r
++ * versions. */\r
++ fprintf (stderr, "\\r
++A caller requested deprecated output format version %d, which may not\n\\r
++be supported in the future.\n", notmuch_format_version);\r
++ }\r
++}\r
++\r
+ static void\r
+ exec_man (const char *page)\r
+ {\r
+@@ -242,6 +271,9 @@ main (int argc, char *argv[])\r
+ g_mime_init (0);\r
+ g_type_init ();\r
+ \r
++ /* Globally default to the current output format version. */\r
++ notmuch_format_version = NOTMUCH_FORMAT_CUR;\r
++\r
+ if (argc == 1)\r
+ return notmuch (local);\r
+ \r
+-- \r
+1.7.10.4\r
+\r
projects / notmuch-archives.git / commitdiff