pref: add support for `-dump-files -` and for `-dump-modules -`

cmd/v/help/build-c.txt

@@ -239,7 +239,15 @@ see also `v help build`.
 
    -dump-c-flags file.txt
       Write all C flags into `file.txt`, one flag per line.
-      If `file.txt` is `-`, then write the flags to stdout, one flag per line.
+      If `file.txt` is `-`, write to stdout instead.
+
+   -dump-modules file.txt
+      Write all module names used by the program in `file.txt`, one module per line.
+      If `file.txt` is `-`, write to stdout instead.
+
+   -dump-files file.txt
+      Write all used V file paths used by the program in `file.txt`, one module per line.
+      If `file.txt` is `-`, write to stdout instead.
 
    -no-rsp
       By default, V passes all C compiler options to the backend C compiler

vlib/v/builder/builder.v

@@ -215,6 +215,9 @@ pub fn (mut b Builder) parse_imports() {
 		}
 		exit(0)
 	}
+	if b.pref.dump_files != '' {
+		b.dump_files(b.parsed_files.map(it.path))
+	}
 	b.rebuild_modules()
 }
 
@@ -241,6 +244,7 @@ pub fn (mut b Builder) resolve_deps() {
 	for node in deps_resolved.nodes {
 		mods << node.name
 	}
+	b.dump_modules(mods)
 	if b.pref.is_verbose {
 		eprintln('------ imported modules: ------')
 		eprintln(mods.str())

vlib/v/builder/cc.v

@@ -483,17 +483,6 @@ fn (mut v Builder) setup_output_name() {
 	v.ccoptions.o_args << '-o "$v.pref.out_name"'
 }
 
-fn (mut v Builder) dump_c_options(all_args []string) {
-	if v.pref.dump_c_flags != '' {
-		non_empty_args := all_args.filter(it != '').join('\n') + '\n'
-		if v.pref.dump_c_flags == '-' {
-			print(non_empty_args)
-		} else {
-			os.write_file(v.pref.dump_c_flags, non_empty_args) or { panic(err) }
-		}
-	}
-}
-
 pub fn (mut v Builder) cc() {
 	if os.executable().contains('vfmt') {
 		return

vlib/v/builder/dump_lists.v

@@ -0,0 +1,26 @@
+module builder
+
+import os
+
+pub fn (b &Builder) dump_c_options(all_args []string) {
+	dump_list(b.pref.dump_c_flags, all_args)
+}
+
+pub fn (b &Builder) dump_modules(mods []string) {
+	dump_list(b.pref.dump_modules, mods)
+}
+
+pub fn (b &Builder) dump_files(files []string) {
+	dump_list(b.pref.dump_files, files)
+}
+
+fn dump_list(file_path string, list []string) {
+	if file_path != '' {
+		content := list.filter(it != '').join('\n') + '\n'
+		if file_path == '-' {
+			print(content)
+		} else {
+			os.write_file(file_path, content) or { panic(err) }
+		}
+	}
+}

vlib/v/pref/pref.v

@@ -139,6 +139,8 @@ pub mut:
 	show_callgraph         bool   // -show-callgraph, print the program callgraph, in a Graphviz DOT format to stdout
 	show_depgraph          bool   // -show-depgraph, print the program module dependency graph, in a Graphviz DOT format to stdout
 	dump_c_flags           string // `-dump-c-flags file.txt` - let V store all C flags, passed to the backend C compiler in `file.txt`, one C flag/value per line.
+	dump_modules           string // `-dump-modules modules.txt` - let V store all V modules, that were used by the compiled program in `modules.txt`, one module per line.
+	dump_files             string // `-dump-files files.txt` - let V store all V or .template file paths, that were used by the compiled program in `files.txt`, one path per line.
 	use_cache              bool   // when set, use cached modules to speed up subsequent compilations, at the cost of slower initial ones (while the modules are cached)
 	retry_compilation      bool = true // retry the compilation with another C compiler, if tcc fails.
 	// TODO Convert this into a []string
@@ -528,6 +530,14 @@ pub fn parse_args_and_show_errors(known_external_commands []string, args []strin
 				res.dump_c_flags = cmdline.option(current_args, arg, '-')
 				i++
 			}
+			'-dump-modules' {
+				res.dump_modules = cmdline.option(current_args, arg, '-')
+				i++
+			}
+			'-dump-files' {
+				res.dump_files = cmdline.option(current_args, arg, '-')
+				i++
+			}
 			'-experimental' {
 				res.experimental = true
 			}