Implement --json query format

The existing --xml output is extremely useful when inspecting oddities,
but the format is such an eyesore. JSON is much saner to look at.

docs/man/rpm.8.md

@@ -66,7 +66,7 @@ query-options
 
 General: \[**\--changelog**\] \[**\--changes**\] \[**\--dupes**\]
 \[**-i,\--info**\] \[**\--last**\] \[**\--qf,\--queryformat
-***QUERYFMT*\] \[**\--xml**\]
+***QUERYFMT*\] \[**\--xml**\] \[**\--json**\]
 
 Dependencies: \[**\--conflicts**\] \[**\--enhances**\]
 \[**\--obsoletes**\] \[**\--provides**\] \[**\--recommends**\]
@@ -552,6 +552,10 @@ Alternate output formats may be requested by following the tag with
 :   Human readable number (in SI). The suffix K = 1000, M = 1000000,
     \...
 
+**:json**
+
+:   Wrap data in JSON.
+
 **:perms**
 
 :   Format file permissions.

include/rpm/rpmtd.h

@@ -253,6 +253,7 @@ typedef enum rpmtdFormats_e {
     RPMTD_FORMAT_HUMANIEC	= 21,	/* human readable value, K = 1024 (int types) */
     RPMTD_FORMAT_TAGNAME	= 22,	/* tag name (any type) */
     RPMTD_FORMAT_TAGNUM		= 23,	/* tag number (any type) */
+    RPMTD_FORMAT_JSON		= 24,	/* json format (any type) */
 } rpmtdFormats;
 
 /** \ingroup rpmtd

lib/formats.c

@@ -339,6 +339,81 @@ static char * xmlFormat(rpmtd td, char **emsg)
     return val;
 }
 
+static char *jsonEscape(const char *s)
+{
+    char *es = NULL;
+    rstrcat(&es, "\"");
+    for (const char *c = s; *c != '\0'; c++) {
+	const char *ec = NULL;
+	switch (*c) {
+	case '\b':
+	    ec = "\\b";
+	    break;
+	case '\f':
+	    ec = "\\f";
+	    break;
+	case '\n':
+	    ec = "\\n";
+	    break;
+	case '\r':
+	    ec = "\\r";
+	    break;
+	case '\t':
+	    ec = "\\t";
+	    break;
+	case '"':
+	    ec = "\\\"";
+	    break;
+	case '\\':
+	    ec = "\\\\";
+	    break;
+	default:
+	    break;
+	}
+
+	if (ec) {
+	    rstrcat(&es, ec);
+	} else if (*c > 0 && *c < 0x20) {
+	    char *uc = NULL;
+	    rasprintf(&uc, "\\u%04x", *c);
+	    rstrcat(&es, uc);
+	    free(uc);
+	} else {
+	    char t[2] = " ";
+	    *t = *c;
+	    rstrcat(&es, t);
+	}
+    }
+    rstrcat(&es, "\"");
+    return es;
+}
+
+static char *jsonFormat(rpmtd td, char **emsg)
+{
+    int escape = 1;
+    char *val = NULL;
+
+    switch (rpmtdClass(td)) {
+    case RPM_BINARY_CLASS:
+	/* we don't want newlines in the binary output */
+	val = rpmBase64Encode(td->data, td->count, 0);
+	break;
+    case RPM_NUMERIC_CLASS:
+	escape = 0;
+	/* fallthrough */
+    default:
+	val = stringFormat(td, emsg);
+	break;
+    }
+
+    if (escape) {
+	char *s = jsonEscape(val);
+	free(val);
+	val = s;
+    }
+    return val;
+}
+
 /* signature fingerprint and time formatting */
 static char * pgpsigFormat(rpmtd td, char **emsg)
 {
@@ -545,6 +620,8 @@ static const struct headerFmt_s rpmHeaderFormats[] = {
 	RPM_ANY_CLASS,		tagnameFormat },
     { RPMTD_FORMAT_TAGNUM,	"tagnum",
 	RPM_ANY_CLASS,		tagnumFormat },
+    { RPMTD_FORMAT_JSON,	"json",
+	RPM_ANY_CLASS,		jsonFormat },
     { -1,			NULL, 		0,	NULL }
 };
 

lib/headerfmt.c

@@ -301,6 +301,66 @@ static struct xformat_s xformat_xml = {
     .xTagFooter = xmlTagFooter,
 };
 
+static void jsonHeader(headerSprintfArgs hsa)
+{
+    hsaAppend(hsa, "{\n");
+}
+
+static void jsonFooter(headerSprintfArgs hsa)
+{
+    /*
+     * XXX HACK: when iterating through the header tags, we don't know
+     * which element will be the last one. We have to emit ',' for each
+     * tag we process and then delete the last one here.
+     */
+    hsa->vallen -= 2;
+    hsaAppend(hsa, "\n}\n");
+}
+
+static void jsonTagHeader(headerSprintfArgs hsa, rpmTagVal tag, int nelem)
+{
+    char *tagname = tagName(tag);
+    hsaAppend(hsa, "    \"");
+    hsaAppend(hsa, tagname);
+    hsaAppend(hsa, "\": ");
+    if (nelem > 1)
+	hsaAppend(hsa, "[\n");
+    free(tagname);
+}
+
+static void jsonTagFooter(headerSprintfArgs hsa, rpmTagVal tag, int nelem)
+{
+    if (nelem > 1)
+	hsaAppend(hsa, "    ]");
+    hsaAppend(hsa, ",");
+    hsaAppend(hsa, "\n");
+}
+
+static void jsonItemHeader(headerSprintfArgs hsa, rpmTagVal tag,
+				int n, int nelem)
+{
+    hsaAppend(hsa, "\t");
+}
+
+static void jsonItemFooter(headerSprintfArgs hsa, rpmTagVal tag,
+				int n, int nelem)
+{
+    if (nelem > 1) {
+	if (n < nelem-1)
+	    hsaAppend(hsa, ",");
+	hsaAppend(hsa, "\n");
+    }
+}
+
+static struct xformat_s xformat_json = {
+    .xHeader = jsonHeader,
+    .xFooter = jsonFooter,
+    .xTagHeader = jsonTagHeader,
+    .xTagFooter = jsonTagFooter,
+    .xItemHeader = jsonItemHeader,
+    .xItemFooter = jsonItemFooter,
+};
+
 /**
  * Search tags for a name.
  * @param hsa		headerSprintf args
@@ -886,6 +946,8 @@ char * headerFormat(Header h, const char * fmt, errmsg_t * errmsg)
     if (tag != NULL && tag->tag == -2 && tag->type != NULL) {
 	if (rstreq(tag->type, "xml"))
 	    hsa.xfmt = xformat_xml; /* struct assignment */
+	else if (rstreq(tag->type, "json"))
+	    hsa.xfmt = xformat_json; /* struct assignment */
     }
 
     if (hsa.xfmt.xHeader)

rpmpopt.in

@@ -119,6 +119,9 @@ rpm	alias --changes --qf '[* %{CHANGELOGTIME:date} %{CHANGELOGNAME}\n%{CHANGELOG
 rpm	alias --xml --qf '[%{*:xml}\n]' \
 	--POPTdesc=$"list metadata in xml"
 
+rpm	alias --json --qf '[%{*:json}]' \
+	--POPTdesc=$"list metadata in JSON"
+
 rpm	alias --triggerscripts --qf '\
 [trigger%{TRIGGERTYPE} scriptlet (using %{TRIGGERSCRIPTPROG}) -- %{TRIGGERCONDS}\n\
 %{TRIGGERSCRIPTS}\n]'