Fix package-named module imports

docs/packages.md

@@ -81,29 +81,39 @@ installs; the next install records the hashes. `pkg list` output is
 unchanged.
 
 Each dependency lands in `flint_modules/<name>/` with its sources and
-its own `flint.toml`:
+its own `flint.toml`. A package can expose its default module as
+`main.fl`, as a same-named file such as `levenshtein/levenshtein.fl`,
+or as a flat `flint_modules/<name>.fl` file.
 
 ```text
 flint_modules/
   libfoo/
     flint.toml
-    foo.fl
+    main.fl
+  levenshtein/
+    flint.toml
+    levenshtein.fl
 ```
 
 ## imports and resolution
 
 ```flint
-import "libfoo/foo.fl"
-print(foo.hello())
+import libfoo
+print(libfoo.hello())
+
+import levenshtein
+print(levenshtein.distance("kitten", "sitting"))
 
 import "gitlib/g.fl"
 print(g.greet())
 ```
 
-A quoted path with a `/` or a `.fl` extension is a file: relative to the
-importing file, except `flint_modules/` is also searched, and packages
-resolve before the standard library. A bare name (`import math`) is the
-standard library.
+A bare name first checks installed packages in `flint_modules/`:
+`<name>/main.fl`, then `<name>/<name>.fl`, then the flat
+`<name>.fl` layout. If no package matches, the standard library is
+checked (so `import math` still imports the library). A quoted path with
+a `/` or a `.fl` extension can address a file relative to the importing
+file; package-internal paths are also resolved from `flint_modules/`.
 
 ## transitive dependencies
 

rust/flintlang/c-src/src/runtime/sys.c

@@ -482,6 +482,21 @@ char *sys_resolve_module(const char *path)
 						        main_file);
 						free(main_file);
 					}
+					/*
+					 * Also support a single-file package named after
+					 * itself, e.g. levenshtein/levenshtein.fl.
+					 */
+					if (found == NULL) {
+						size_t need_named = strlen(dir_main) + 1 +
+						        pathlen + 3 + 1;
+						char *named = malloc(need_named);
+						if (named != NULL) {
+							snprintf(named, need_named, "%s/%s.fl",
+							        dir_main, path);
+							found = pkg_candidate(named);
+							free(named);
+						}
+					}
 					if (found == NULL) {
 						size_t need2 =
 						        strlen(dir_main) + 4;

src/runtime/sys.c

@@ -482,6 +482,21 @@ char *sys_resolve_module(const char *path)
 						        main_file);
 						free(main_file);
 					}
+					/*
+					 * Also support a single-file package named after
+					 * itself, e.g. levenshtein/levenshtein.fl.
+					 */
+					if (found == NULL) {
+						size_t need_named = strlen(dir_main) + 1 +
+						        pathlen + 3 + 1;
+						char *named = malloc(need_named);
+						if (named != NULL) {
+							snprintf(named, need_named, "%s/%s.fl",
+							        dir_main, path);
+							found = pkg_candidate(named);
+							free(named);
+						}
+					}
 					if (found == NULL) {
 						size_t need2 =
 						        strlen(dir_main) + 4;

tests/pkg_test.sh

@@ -123,7 +123,7 @@ cat > "$WORK/gitsrc/flint.toml" <<'EOF'
 name = "shout"
 version = "0.3.0"
 EOF
-cat > "$WORK/gitsrc/main.fl" <<'EOF'
+cat > "$WORK/gitsrc/shout.fl" <<'EOF'
 export fn loud(who) {
     return "HEY " + who
 }
@@ -158,7 +158,7 @@ expect "git import works" "HEY zed" "$("$FLINT" use.fl 2>&1)"
 pin=$(sed -n '/^commit = /s/commit = "\(.*\)"/\1/p' flint.lock)
 expect "lock pins a 40-char commit" "40" "${#pin}"
 
-cat > "$WORK/gitsrc/main.fl" <<'EOF'
+cat > "$WORK/gitsrc/shout.fl" <<'EOF'
 export fn loud(who) {
     return "LOUDER " + who
 }