docs: mention _cgfs/opts.json in README

The inconsistently named `cg.toJSON` has been renamed to
`cg.fmt.json.serialize`. The code has also been restructured to fit more
formats in the future.

README.md

@@ -79,8 +79,9 @@ confgenfs /path/to/confgen.lua ~/confgenfs
 This mounts a FUSE3 filesystem containing all the config files. The advantage of this is that
 the templates will be generated when the file is opened and not ahead of time.
 
-Additionally, the filesystem will contain "meta-files" inside `_cgfs/`, currently only `_cgfs/eval`.
-You can write some Lua code to this file, and it will be evaluated in the global Lua context.
+Additionally, the filesystem will contain "meta-files" inside `_cgfs/`, currently only `_cgfs/eval`
+and `_cgfs/opts.json`.
+You can write some Lua code to the former file, and it will be evaluated in the global Lua context.
 This allows for dynamic configurations, here's a practical example:
 
 `.config/waybar/config.cgt`:

build.zig.zon

@@ -1,6 +1,6 @@
 .{
     .name = "confgen",
-    .version = "0.5.0",
+    .version = "0.6.0",
 
     .dependencies = .{
         .zig_args = .{

confgen/main.zig

@@ -66,6 +66,20 @@ pub fn main() u8 {
                 , .{usage});
             },
             error.Explained => {},
+            error.LuaError => {
+                // Once Zig is smart enough to remove LuaError from the error set here, we'll
+                // replace this branch with this compile-time check:
+                //comptime {
+                //    const ret_errors = @typeInfo(@typeInfo(@typeInfo(@TypeOf(run)).Fn.return_type.?).ErrorUnion.error_set).ErrorSet.?;
+                //    for (ret_errors) |err| {
+                //        if (std.mem.eql(u8, err.name, "LuaError"))
+                //            @compileError("Run function must never return a LuaError!");
+                //    }
+                //}
+
+                // We can't get the error message here as the Lua state will alread have been destroyed.
+                std.log.err("UNKNOWN LUA ERROR! THIS IS A BUG!", .{});
+            },
             else => {
                 std.log.err("UNEXPECTED: {s}", .{@errorName(e)});
                 if (@errorReturnTrace()) |ert| std.debug.dumpStackTrace(ert.*);
@@ -144,14 +158,14 @@ pub fn run() !void {
         libcg.c.lua_getfield(l, -1, "opt");
 
         if (arg.positionals.len == 0) {
-            try libcg.json.luaToJSON(l, &wstream);
+            try libcg.format.formats.json.luaToJSON(l, &wstream);
             libcg.c.lua_pop(l, 1);
         } else {
             try wstream.beginObject();
             for (arg.positionals) |opt| {
                 try wstream.objectField(opt);
                 libcg.c.lua_getfield(l, -1, opt);
-                try libcg.json.luaToJSON(l, &wstream);
+                try libcg.format.formats.json.luaToJSON(l, &wstream);
             }
             libcg.c.lua_pop(l, 2);
             try wstream.endObject();

confgenfs/FileSystem.zig

@@ -575,7 +575,7 @@ fn generateOptsJSON(self: *FileSystem) ![]const u8 {
     libcg.c.lua_getglobal(self.l, "cg");
     libcg.c.lua_getfield(self.l, -1, "opt");
 
-    try libcg.json.luaToJSON(self.l, &wstream);
+    try libcg.format.formats.json.luaToJSON(self.l, &wstream);
 
     return try buf.toOwnedSlice();
 }

libcg/format.zig

@@ -0,0 +1,16 @@
+const std = @import("std");
+const ffi = @import("ffi.zig");
+const c = ffi.c;
+
+pub const formats = struct {
+    pub const json = @import("format/json.zig");
+};
+
+pub fn pushFmtTable(l: *c.lua_State) void {
+    c.lua_createtable(l, 0, @typeInfo(formats).Struct.decls.len);
+
+    inline for (@typeInfo(formats).Struct.decls) |decl| {
+        @field(formats, decl.name).luaPush(l);
+        c.lua_setfield(l, -2, decl.name);
+    }
+}

libcg/format/json.zig

@@ -1,9 +1,17 @@
 //! Tools for serialization of Lua values to JSON
 //! Used by the --json-opt flag
 const std = @import("std");
-const ffi = @import("ffi.zig");
+const ffi = @import("../ffi.zig");
 const c = ffi.c;
 
+const luaapi = @import("../luaapi.zig");
+
+pub fn luaPush(l: *c.lua_State) void {
+    c.lua_createtable(l, 0, 1);
+    c.lua_pushcfunction(l, ffi.luaFunc(lSerialize));
+    c.lua_setfield(l, -2, "serialize");
+}
+
 /// Writes a lua object to the stream. stream must be a json.WriteStream
 pub fn luaToJSON(l: *c.lua_State, stream: anytype) !void {
     const ty = c.lua_type(l, -1);
@@ -71,3 +79,29 @@ pub fn luaToJSON(l: *c.lua_State, stream: anytype) !void {
         else => unreachable,
     }
 }
+
+fn lSerialize(l: *c.lua_State) !c_int {
+    c.luaL_checkany(l, 1);
+    const pretty = if (c.lua_gettop(l) >= 2) c.lua_toboolean(l, 2) != 0 else false;
+
+    const state = luaapi.getState(l);
+
+    // If you're doing more than 16KiB of JSON, open an issue
+    // and bring a VERY good explanation with you :D
+    var buf: [1024 * 16]u8 = undefined;
+    var fbs = std.io.fixedBufferStream(&buf);
+
+    var wstream = std.json.WriteStream(@TypeOf(fbs.writer()), .assumed_correct).init(
+        state.files.allocator,
+        fbs.writer(),
+        .{ .whitespace = if (pretty) .indent_2 else .minified },
+    );
+    defer wstream.deinit();
+
+    c.lua_pushvalue(l, 1);
+    try @import("json.zig").luaToJSON(l, &wstream);
+
+    const written = fbs.getWritten();
+    c.lua_pushlstring(l, written.ptr, written.len);
+    return 1;
+}

libcg/luaapi.zig

@@ -1,6 +1,8 @@
 const std = @import("std");
 const ffi = @import("ffi.zig");
 const c = ffi.c;
+
+const format = @import("format.zig");
 const luagen = @import("luagen.zig");
 
 const TemplateCode = luagen.TemplateCode;
@@ -92,12 +94,12 @@ pub fn initLuaState(cgstate: *CgState) !*c.lua_State {
     c.lua_pushcfunction(l, ffi.luaFunc(lOnDone));
     c.lua_setfield(l, -2, "onDone");
 
-    c.lua_pushcfunction(l, ffi.luaFunc(lToJSON));
-    c.lua_setfield(l, -2, "toJSON");
-
     c.lua_pushcfunction(l, ffi.luaFunc(lFileIter));
     c.lua_setfield(l, -2, "fileIter");
 
+    format.pushFmtTable(l);
+    c.lua_setfield(l, -2, "fmt");
+
     // add cg table to globals
     c.lua_setglobal(l, "cg");
 
@@ -187,12 +189,17 @@ pub fn generate(l: *c.lua_State, code: TemplateCode) !GeneratedFile {
 
     if (c.lua_pcall(l, 0, 0, 0) != 0) {
         std.log.err("failed to run template: {?s}", .{ffi.luaToString(l, -1)});
-
         return error.RunTemplate;
     }
 
     return .{
-        .content = try tmpl.getOutput(l),
+        .content = tmpl.getOutput(l) catch |e| switch (e) {
+            error.LuaError => {
+                std.log.err("failed to run post-processor: {?s}", .{ffi.luaToString(l, -1)});
+                return error.RunPostProcessor;
+            },
+            else => return e,
+        },
         .mode = tmpl.mode,
         .assume_deterministic = tmpl.assume_deterministic,
     };
@@ -503,32 +510,6 @@ fn lOnDone(l: *c.lua_State) !c_int {
     return 0;
 }
 
-fn lToJSON(l: *c.lua_State) !c_int {
-    c.luaL_checkany(l, 1);
-    const pretty = if (c.lua_gettop(l) >= 2) c.lua_toboolean(l, 2) != 0 else false;
-
-    const state = getState(l);
-
-    // If you're doing more than 16KiB of JSON, open an issue
-    // and bring a VERY good explanation with you :D
-    var buf: [1024 * 16]u8 = undefined;
-    var fbs = std.io.fixedBufferStream(&buf);
-
-    var wstream = std.json.WriteStream(@TypeOf(fbs.writer()), .assumed_correct).init(
-        state.files.allocator,
-        fbs.writer(),
-        .{ .whitespace = if (pretty) .indent_2 else .minified },
-    );
-    defer wstream.deinit();
-
-    c.lua_pushvalue(l, 1);
-    try @import("json.zig").luaToJSON(l, &wstream);
-
-    const written = fbs.getWritten();
-    c.lua_pushlstring(l, written.ptr, written.len);
-    return 1;
-}
-
 fn lFileIter(l: *c.lua_State) !c_int {
     const state = getState(l);
 
@@ -650,7 +631,6 @@ pub const LTemplate = struct {
     /// caller owns return value.
     fn getOutput(self: *LTemplate, l: *c.lua_State) ![]const u8 {
         const top = c.lua_gettop(l);
-        defer c.lua_settop(l, top);
 
         c.lua_pushlightuserdata(l, self);
         c.lua_gettable(l, c.LUA_REGISTRYINDEX);
@@ -659,6 +639,7 @@ pub const LTemplate = struct {
 
         // check if there's no post processor
         if (c.lua_isnil(l, -1)) {
+            c.lua_settop(l, top);
             return try self.output.allocator.dupe(u8, self.output.items);
         }
 
@@ -667,11 +648,14 @@ pub const LTemplate = struct {
         // call post processor
         if (c.lua_pcall(l, 1, 1, 0) != 0) {
             try ffi.luaFmtString(l, "running post processor: {?s}", .{ffi.luaToString(l, -1)});
+            c.lua_insert(l, top + 1);
+            c.lua_settop(l, top + 1);
             return error.LuaError;
         }
 
         const out = ffi.luaConvertString(l, -1);
 
+        c.lua_settop(l, top);
         return try self.output.allocator.dupe(u8, out);
     }
 

libcg/main.zig

@@ -2,7 +2,7 @@ const std = @import("std");
 pub const c = ffi.c;
 
 pub const ffi = @import("ffi.zig");
-pub const json = @import("json.zig");
+pub const format = @import("format.zig");
 pub const luaapi = @import("luaapi.zig");
 pub const luagen = @import("luagen.zig");
 

share/man/man3/confgen.3

@@ -133,7 +133,7 @@ Example:
 .B cg.onDone(function(errors) print(\(dqHad errors: \(dq .. tostring(errors)) end)
 
 .TP
-.B cg.toJSON(value[, pretty])
+.B cg.fmt.json.serialize(value[, pretty])
 Convert an arbitrary lua value to JSON and return that as a string. The JSON will be minified by
 default unless
 .IR pretty \ is \ true .
@@ -144,7 +144,7 @@ will be serialized as
 .IR null .
 
 Example:
-.B local json = cg.toJSON({ x = \(dqy\(dq }) -- '{\(dqx\(dq: \(dqy\(dq}'
+.B local json = cg.fmt.json.serialize({ x = \(dqy\(dq }) -- '{\(dqx\(dq: \(dqy\(dq}'
 
 .TP
 .B cg.fileIter()