manifest: support path dependencies (#1048)

This PR introduces path dependency [like Cargo's
one](https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#specifying-path-dependencies).
Path dependency specify a local directory as dependency.
[Unlike Cargo's
one](https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#no-local-path-traversal),

- currently poac doesn't care about `poac.toml` in the path.
- Like git dependency, path dependency implemented by this PR supports
only header-only library.
- poac doesn't support `version` for published package.

This PR doesn't contain `poac add --path` sub-command option.

Poac with this PR can allow `poac.toml` like below:

```toml
[dependencies]
local_header_only_library = {path = "./path/to/library"}
```

---------

Co-authored-by: Ken Matsui <[email protected]>

docs/usage.md

@@ -50,7 +50,9 @@ Poac uses a cache since we executed the command with no changes.
 
 ## Install dependencies
 
-Like Cargo does, Poac installs dependencies at build time.  Poac currently supports Git and system dependencies.  You can use the `poac add` command to add dependencies to your project.
+Like Cargo does, Poac installs dependencies at build time.  Poac currently supports Git, path, and system dependencies.  You can use two ways to add dependencies to your project: using the `poac add` command and editing `poac.toml` directly.
+
+### `poac add`
 
 The `poac add` command accepts the following arguments:
 
@@ -69,6 +71,23 @@ poac add libgit2 --sys --version "1.1.0"
 poac add "ToruNiina/toml11" --rev "846abd9a49082fe51440aa07005c360f13a67bbf"
 ```
 
+### Editing `poac.toml` directly
+
+The syntax for `poac.toml` is as follows:
+
+```toml
+[dependencies]
+
+# git dependency
+"ToruNiina/toml11" = { git = "https://github.com/ToruNiina/toml11.git", rev = "846abd9a49082fe51440aa07005c360f13a67bbf" }
+
+# path dependency
+local_lib = { path = "../local_lib" }
+
+# system dependency
+fmt = { version = ">= 9", system = true }
+```
+
 If `tag`, `branch`, or `rev` is unspecified for git dependencies, Poac will use the latest revision of the default branch. System dependency names must be acceptable by `pkg-config`. The version requirement syntax is specified in [src/VersionReq.hpp](https://github.com/poac-dev/poac/blob/main/src/VersionReq.hpp).
 
 After adding dependencies, executing the `build` command will install the package and its dependencies.

src/Manifest.cc

@@ -19,6 +19,7 @@
 #include <toml.hpp>
 #include <unordered_map>
 #include <unordered_set>
+#include <utility>
 #include <variant>
 #include <vector>
 
@@ -126,13 +127,23 @@ struct GitDependency {
   DepMetadata install() const;
 };
 
+struct PathDependency {
+  std::string name;
+  std::string path;
+
+  DepMetadata install() const;
+};
+
 struct SystemDependency {
   std::string name;
   VersionReq versionReq;
 
   DepMetadata install() const;
 };
 
+using Dependency =
+    std::variant<GitDependency, PathDependency, SystemDependency>;
+
 void
 Profile::merge(const Profile& other) {
   cxxflags.insert(other.cxxflags.begin(), other.cxxflags.end());
@@ -166,10 +177,8 @@ struct Manifest {
   std::optional<toml::value> data = std::nullopt;
 
   std::optional<Package> package = std::nullopt;
-  std::optional<std::vector<std::variant<GitDependency, SystemDependency>>>
-      dependencies = std::nullopt;
-  std::optional<std::vector<std::variant<GitDependency, SystemDependency>>>
-      devDependencies = std::nullopt;
+  std::optional<std::vector<Dependency>> dependencies = std::nullopt;
+  std::optional<std::vector<Dependency>> devDependencies = std::nullopt;
 
   std::optional<Profile> profile = std::nullopt;
   std::optional<Profile> devProfile = std::nullopt;
@@ -536,6 +545,16 @@ parseGitDep(const std::string& name, const toml::table& info) {
   return { .name = name, .url = gitUrlStr, .target = target };
 }
 
+static PathDependency
+parsePathDep(const std::string& name, const toml::table& info) {
+  validateDepName(name);
+  const auto& path = info.at("path");
+  if (!path.is_string()) {
+    throw PoacError("path dependency must be a string");
+  }
+  return { .name = name, .path = path.as_string() };
+}
+
 static SystemDependency
 parseSystemDep(const std::string& name, const toml::table& info) {
   validateDepName(name);
@@ -548,7 +567,7 @@ parseSystemDep(const std::string& name, const toml::table& info) {
   return { .name = name, .versionReq = VersionReq::parse(versionReq) };
 }
 
-static std::optional<std::vector<std::variant<GitDependency, SystemDependency>>>
+static std::optional<std::vector<Dependency>>
 parseDependencies(const char* key) {
   Manifest& manifest = Manifest::instance();
   const auto& table = toml::get<toml::table>(manifest.data.value());
@@ -558,7 +577,7 @@ parseDependencies(const char* key) {
   }
   const auto tomlDeps = toml::find<toml::table>(manifest.data.value(), key);
 
-  std::vector<std::variant<GitDependency, SystemDependency>> deps;
+  std::vector<Dependency> deps;
   for (const auto& dep : tomlDeps) {
     if (dep.second.is_table()) {
       const auto& info = dep.second.as_table();
@@ -568,11 +587,15 @@ parseDependencies(const char* key) {
       } else if (info.contains("system") && info.at("system").as_boolean()) {
         deps.emplace_back(parseSystemDep(dep.first, info));
         continue;
+      } else if (info.contains("path")) {
+        deps.emplace_back(parsePathDep(dep.first, info));
+        continue;
       }
     }
 
     throw PoacError(
-        "Only Git dependency and system dependency are supported for now: ",
+        "Only Git dependency, path dependency, and system dependency are "
+        "supported for now: ",
         dep.first
     );
   }
@@ -619,6 +642,29 @@ GitDependency::install() const {
   return { .includes = includes, .libs = "" };
 }
 
+DepMetadata
+PathDependency::install() const {
+  const fs::path installDir = fs::weakly_canonical(path);
+  if (fs::exists(installDir) && !fs::is_empty(installDir)) {
+    logger::debug("{} is already installed", name);
+  } else {
+    throw PoacError(installDir.string() + " can't be accessible as directory");
+  }
+
+  const fs::path includeDir = installDir / "include";
+  std::string includes = "-isystem";
+
+  if (fs::exists(includeDir) && fs::is_directory(includeDir)
+      && !fs::is_empty(includeDir)) {
+    includes += includeDir.string();
+  } else {
+    includes += installDir.string();
+  }
+
+  // Currently, no libs are supported.
+  return { .includes = includes, .libs = "" };
+}
+
 DepMetadata
 SystemDependency::install() const {
   const std::string pkgConfigVer = versionReq.toPkgConfigString(name);