Allow for shorter app headers

compiler/load/tests/fixtures/build/app_with_deps/Quicksort.roc

@@ -1,6 +1,4 @@
-app "quicksort"
-    packages { base: "./platform" }
-    provides [ swap, partition, partitionHelp, quicksort ] to base
+app "quicksort" provides [ swap, partition, partitionHelp, quicksort ] to "./platform"
 
 quicksort : List (Num a), Int, Int -> List (Num a)
 quicksort = \list, low, high ->

compiler/load/tests/fixtures/build/app_with_deps/QuicksortOneDef.roc

@@ -1,4 +1,4 @@
-app "quicksort" packages { base: "./platform" } provides [ quicksort ] to base
+app "quicksort" provides [ quicksort ] to "./platform"
 
 quicksort = \originalList ->
     quicksortHelp : List (Num a), Int, Int -> List (Num a)

compiler/parse/src/header.rs

@@ -76,13 +76,19 @@ pub struct InterfaceHeader<'a> {
     pub after_imports: &'a [CommentOrNewline<'a>],
 }
 
+#[derive(Clone, Debug, PartialEq)]
+pub enum To<'a> {
+    ExistingPackage(&'a str),
+    NewPackage(PackageOrPath<'a>),
+}
+
 #[derive(Clone, Debug, PartialEq)]
 pub struct AppHeader<'a> {
     pub name: Loc<StrLiteral<'a>>,
     pub packages: Vec<'a, Loc<PackageEntry<'a>>>,
     pub imports: Vec<'a, Loc<ImportsEntry<'a>>>,
     pub provides: Vec<'a, Loc<ExposesEntry<'a, &'a str>>>,
-    pub to: Loc<&'a str>,
+    pub to: Loc<To<'a>>,
 
     // Potential comments and newlines - these will typically all be empty.
     pub after_app_keyword: &'a [CommentOrNewline<'a>],
@@ -256,7 +262,7 @@ pub fn package_entry<'a>() -> impl Parser<'a, PackageEntry<'a>> {
     }
 }
 
-fn package_or_path<'a>() -> impl Parser<'a, PackageOrPath<'a>> {
+pub fn package_or_path<'a>() -> impl Parser<'a, PackageOrPath<'a>> {
     map!(
         either!(
             string_literal::parse(),

compiler/parse/src/module.rs

@@ -2,13 +2,14 @@ use crate::ast::{Attempting, CommentOrNewline, Def, Module};
 use crate::blankspace::{space0, space0_around, space0_before, space1};
 use crate::expr::def;
 use crate::header::{
-    package_entry, AppHeader, Effects, ExposesEntry, ImportsEntry, InterfaceHeader, ModuleName,
-    PackageEntry, PackageName, PlatformHeader, TypedIdent,
+    package_entry, package_or_path, AppHeader, Effects, ExposesEntry, ImportsEntry,
+    InterfaceHeader, ModuleName, PackageEntry, PackageName, PackageOrPath, PlatformHeader, To,
+    TypedIdent,
 };
 use crate::ident::{lowercase_ident, unqualified_ident, uppercase_ident};
 use crate::parser::{
     self, ascii_char, ascii_string, loc, optional, peek_utf8_char, peek_utf8_char_at, unexpected,
-    unexpected_eof, ParseResult, Parser, State,
+    unexpected_eof, Either, ParseResult, Parser, State,
 };
 use crate::string_literal;
 use crate::type_annotation;
@@ -293,7 +294,7 @@ pub fn module_defs<'a>() -> impl Parser<'a, Vec<'a, Located<Def<'a>>>> {
 
 struct ProvidesTo<'a> {
     entries: Vec<'a, Located<ExposesEntry<'a, &'a str>>>,
-    to: Located<&'a str>,
+    to: Located<To<'a>>,
 
     before_provides_keyword: &'a [CommentOrNewline<'a>],
     after_provides_keyword: &'a [CommentOrNewline<'a>],
@@ -316,14 +317,30 @@ fn provides_to<'a>() -> impl Parser<'a, ProvidesTo<'a>> {
                 ),
                 and!(
                     space1(1),
-                    skip_first!(ascii_string("to"), and!(space1(1), loc!(lowercase_ident())))
+                    skip_first!(
+                        ascii_string("to"),
+                        and!(
+                            space1(1),
+                            loc!(either!(lowercase_ident(), package_or_path()))
+                        )
+                    )
                 )
             )
         ),
         |(
             (before_provides_keyword, after_provides_keyword),
-            (entries, (before_to_keyword, (after_to_keyword, to))),
+            (entries, (before_to_keyword, (after_to_keyword, loc_to))),
         )| {
+            let loc_to: Located<Either<&'a str, PackageOrPath<'a>>> = loc_to;
+            let to_val = match loc_to.value {
+                Either::First(pkg) => To::ExistingPackage(pkg),
+                Either::Second(pkg) => To::NewPackage(pkg),
+            };
+            let to = Located {
+                value: to_val,
+                region: loc_to.region,
+            };
+
             ProvidesTo {
                 entries,
                 to,

compiler/parse/tests/test_parse.rs

@@ -26,7 +26,9 @@ mod test_parse {
     use roc_parse::ast::{
         self, Attempting, Def, EscapedChar, Spaceable, TypeAnnotation, WhenBranch,
     };
-    use roc_parse::header::{AppHeader, InterfaceHeader, ModuleName};
+    use roc_parse::header::{
+        AppHeader, ExposesEntry, InterfaceHeader, ModuleName, PackageEntry, PackageOrPath, To,
+    };
     use roc_parse::module::{app_header, interface_header, module_defs};
     use roc_parse::parser::{Fail, FailReason, Parser, State};
     use roc_parse::test_helpers::parse_expr_with;
@@ -2211,7 +2213,7 @@ mod test_parse {
             packages,
             imports,
             provides,
-            to: Located::new(0, 0, 53, 57, "blah"),
+            to: Located::new(0, 0, 53, 57, To::ExistingPackage("blah")),
             after_app_keyword: &[],
             before_packages: &[],
             after_packages: &[],
@@ -2237,6 +2239,8 @@ mod test_parse {
 
     #[test]
     fn minimal_app_header() {
+        use PackageOrPath::Path;
+
         let arena = Bump::new();
         let packages = Vec::new_in(&arena);
         let imports = Vec::new_in(&arena);
@@ -2247,7 +2251,7 @@ mod test_parse {
             packages,
             imports,
             provides,
-            to: Located::new(0, 0, 30, 34, "blah"),
+            to: Located::new(0, 0, 30, 38, To::NewPackage(Path(PlainLine("./blah")))),
             after_app_keyword: &[],
             before_packages: &[],
             after_packages: &[],
@@ -2261,7 +2265,7 @@ mod test_parse {
 
         let src = indoc!(
             r#"
-                app "test-app" provides [] to blah
+                app "test-app" provides [] to "./blah"
             "#
         );
         let actual = app_header()
@@ -2273,17 +2277,27 @@ mod test_parse {
 
     #[test]
     fn full_app_header() {
+        use ExposesEntry::Exposed;
+        use PackageOrPath::Path;
+
+        let pkg_entry = PackageEntry::Entry {
+            shorthand: "base",
+            spaces_after_shorthand: &[],
+            package_or_path: Located::new(0, 0, 33, 45, Path(PlainLine("./platform"))),
+        };
+        let loc_pkg_entry = Located::new(0, 0, 27, 45, pkg_entry);
         let arena = Bump::new();
-        let packages = Vec::new_in(&arena);
+        let packages = bumpalo::vec![in &arena; loc_pkg_entry];
         let imports = Vec::new_in(&arena);
-        let provides = Vec::new_in(&arena);
-        let module_name = StrLiteral::PlainLine("test-app");
+        let provide_entry = Located::new(0, 0, 59, 68, Exposed("quicksort"));
+        let provides = bumpalo::vec![in &arena; provide_entry];
+        let module_name = StrLiteral::PlainLine("quicksort");
         let expected = AppHeader {
-            name: Located::new(0, 0, 4, 14, module_name),
+            name: Located::new(0, 0, 4, 15, module_name),
             packages,
             imports,
             provides,
-            to: Located::new(0, 0, 30, 34, "blah"),
+            to: Located::new(0, 0, 74, 78, To::ExistingPackage("base")),
             after_app_keyword: &[],
             before_packages: &[],
             after_packages: &[],

examples/quicksort/Quicksort.roc

@@ -1,4 +1,4 @@
-app "quicksort" packages { base: "./platform" } provides [ quicksort ] to base
+app "quicksort" provides [ main ] to "./platform"
 
 quicksort = \originalList ->