Move flake-related stuff to src/libexpr/flake

1 files changed, 252 insertions, 0 deletions

diff --git a/src/libexpr/flake/flakeref.cc b/src/libexpr/flake/flakeref.cc
new file mode 100644
index 000000000..24af09124
--- /dev/null
+++ b/src/libexpr/flake/flakeref.cc
@@ -0,0 +1,252 @@
+#include "flakeref.hh"
+#include "store-api.hh"
+
+#include <regex>
+
+namespace nix {
+
+// A Git ref (i.e. branch or tag name).
+const static std::string refRegex = "[a-zA-Z0-9][a-zA-Z0-9_.-]*"; // FIXME: check
+
+// A Git revision (a SHA-1 commit hash).
+const static std::string revRegexS = "[0-9a-fA-F]{40}";
+std::regex revRegex(revRegexS, std::regex::ECMAScript);
+
+// A Git ref or revision.
+const static std::string revOrRefRegex = "(?:(" + revRegexS + ")|(" + refRegex + "))";
+
+// A rev ("e72daba8250068216d79d2aeef40d4d95aff6666"), or a ref
+// optionally followed by a rev (e.g. "master" or
+// "master/e72daba8250068216d79d2aeef40d4d95aff6666").
+const static std::string refAndOrRevRegex = "(?:(" + revRegexS + ")|(?:(" + refRegex + ")(?:/(" + revRegexS + "))?))";
+
+const static std::string flakeAlias = "[a-zA-Z][a-zA-Z0-9_-]*";
+
+// GitHub references.
+const static std::string ownerRegex = "[a-zA-Z][a-zA-Z0-9_-]*";
+const static std::string repoRegex = "[a-zA-Z][a-zA-Z0-9_-]*";
+
+// URI stuff.
+const static std::string schemeRegex = "(?:http|https|ssh|git|file)";
+const static std::string authorityRegex = "[a-zA-Z0-9._~-]*";
+const static std::string segmentRegex = "[a-zA-Z0-9._~-]+";
+const static std::string pathRegex = "/?" + segmentRegex + "(?:/" + segmentRegex + ")*";
+
+// 'dir' path elements cannot start with a '.'. We also reject
+// potentially dangerous characters like ';'.
+const static std::string subDirElemRegex = "(?:[a-zA-Z0-9_-]+[a-zA-Z0-9._-]*)";
+const static std::string subDirRegex = subDirElemRegex + "(?:/" + subDirElemRegex + ")*";
+
+
+FlakeRef::FlakeRef(const std::string & uri_, bool allowRelative)
+{
+    // FIXME: could combine this into one regex.
+
+    static std::regex flakeRegex(
+        "(?:flake:)?(" + flakeAlias + ")(?:/(?:" + refAndOrRevRegex + "))?",
+        std::regex::ECMAScript);
+
+    static std::regex githubRegex(
+        "github:(" + ownerRegex + ")/(" + repoRegex + ")(?:/" + revOrRefRegex + ")?",
+        std::regex::ECMAScript);
+
+    static std::regex uriRegex(
+        "((" + schemeRegex + "):" +
+        "(?://(" + authorityRegex + "))?" +
+        "(" + pathRegex + "))",
+        std::regex::ECMAScript);
+
+    static std::regex refRegex2(refRegex, std::regex::ECMAScript);
+
+    static std::regex subDirRegex2(subDirRegex, std::regex::ECMAScript);
+
+    auto [uri2, params] = splitUriAndParams(uri_);
+    std::string uri(uri2);
+
+    auto handleSubdir = [&](const std::string & name, const std::string & value) {
+        if (name == "dir") {
+            if (value != "" && !std::regex_match(value, subDirRegex2))
+                throw BadFlakeRef("flake '%s' has invalid subdirectory '%s'", uri, value);
+            subdir = value;
+            return true;
+        } else
+            return false;
+    };
+
+    auto handleGitParams = [&](const std::string & name, const std::string & value) {
+        if (name == "rev") {
+            if (!std::regex_match(value, revRegex))
+                throw BadFlakeRef("invalid Git revision '%s'", value);
+            rev = Hash(value, htSHA1);
+        } else if (name == "ref") {
+            if (!std::regex_match(value, refRegex2))
+                throw BadFlakeRef("invalid Git ref '%s'", value);
+            ref = value;
+        } else if (handleSubdir(name, value))
+            ;
+        else return false;
+        return true;
+    };
+
+    std::cmatch match;
+    if (std::regex_match(uri.c_str(), match, flakeRegex)) {
+        IsAlias d;
+        d.alias = match[1];
+        if (match[2].matched)
+            rev = Hash(match[2], htSHA1);
+        else if (match[3].matched) {
+            ref = match[3];
+            if (match[4].matched)
+                rev = Hash(match[4], htSHA1);
+        }
+        data = d;
+    }
+
+    else if (std::regex_match(uri.c_str(), match, githubRegex)) {
+        IsGitHub d;
+        d.owner = match[1];
+        d.repo = match[2];
+        if (match[3].matched)
+            rev = Hash(match[3], htSHA1);
+        else if (match[4].matched) {
+            ref = match[4];
+        }
+        for (auto & param : params) {
+            if (handleSubdir(param.first, param.second))
+                ;
+            else
+                throw BadFlakeRef("invalid Git flakeref parameter '%s', in '%s'", param.first, uri);
+        }
+        data = d;
+    }
+
+    else if (std::regex_match(uri.c_str(), match, uriRegex)
+        && (match[2] == "file" || hasSuffix(match[4], ".git")))
+    {
+        IsGit d;
+        d.uri = match[1];
+        for (auto & param : params) {
+            if (handleGitParams(param.first, param.second))
+                ;
+            else
+                // FIXME: should probably pass through unknown parameters
+                throw BadFlakeRef("invalid Git flakeref parameter '%s', in '%s'", param.first, uri);
+        }
+        if (rev && !ref)
+            throw BadFlakeRef("flake URI '%s' lacks a Git ref", uri);
+        data = d;
+    }
+
+    else if ((hasPrefix(uri, "/") || (allowRelative && (hasPrefix(uri, "./") || hasPrefix(uri, "../") || uri == ".")))
+        && uri.find(':') == std::string::npos)
+    {
+        IsPath d;
+        if (allowRelative) {
+            d.path = absPath(uri);
+            while (true) {
+                if (pathExists(d.path + "/.git")) break;
+                subdir = baseNameOf(d.path) + (subdir.empty() ? "" : "/" + subdir);
+                d.path = dirOf(d.path);
+                if (d.path == "/")
+                    throw BadFlakeRef("path '%s' does not reference a Git repository", uri);
+            }
+        } else
+            d.path = canonPath(uri);
+        data = d;
+        for (auto & param : params) {
+            if (handleGitParams(param.first, param.second))
+                ;
+            else
+                throw BadFlakeRef("invalid Git flakeref parameter '%s', in '%s'", param.first, uri);
+        }
+    }
+
+    else
+        throw BadFlakeRef("'%s' is not a valid flake reference", uri);
+}
+
+std::string FlakeRef::to_string() const
+{
+    std::string string;
+    bool first = true;
+
+    auto addParam =
+        [&](const std::string & name, std::string value) {
+            string += first ? '?' : '&';
+            first = false;
+            string += name;
+            string += '=';
+            string += value; // FIXME: escaping
+        };
+
+    if (auto refData = std::get_if<FlakeRef::IsAlias>(&data)) {
+        string = refData->alias;
+        if (ref) string += '/' + *ref;
+        if (rev) string += '/' + rev->gitRev();
+    }
+
+    else if (auto refData = std::get_if<FlakeRef::IsPath>(&data)) {
+        string = refData->path;
+        if (ref) addParam("ref", *ref);
+        if (rev) addParam("rev", rev->gitRev());
+        if (subdir != "") addParam("dir", subdir);
+    }
+
+    else if (auto refData = std::get_if<FlakeRef::IsGitHub>(&data)) {
+        assert(!(ref && rev));
+        string = "github:" + refData->owner + "/" + refData->repo;
+        if (ref) { string += '/'; string += *ref; }
+        if (rev) { string += '/'; string += rev->gitRev(); }
+        if (subdir != "") addParam("dir", subdir);
+    }
+
+    else if (auto refData = std::get_if<FlakeRef::IsGit>(&data)) {
+        assert(!rev || ref);
+        string = refData->uri;
+
+        if (ref) {
+            addParam("ref", *ref);
+            if (rev)
+                addParam("rev", rev->gitRev());
+        }
+
+        if (subdir != "") addParam("dir", subdir);
+    }
+
+    else abort();
+
+    assert(FlakeRef(string) == *this);
+
+    return string;
+}
+
+std::ostream & operator << (std::ostream & str, const FlakeRef & flakeRef)
+{
+    str << flakeRef.to_string();
+    return str;
+}
+
+bool FlakeRef::isImmutable() const
+{
+    return (bool) rev;
+}
+
+FlakeRef FlakeRef::baseRef() const // Removes the ref and rev from a FlakeRef.
+{
+    FlakeRef result(*this);
+    result.ref = std::nullopt;
+    result.rev = std::nullopt;
+    return result;
+}
+
+std::optional<FlakeRef> parseFlakeRef(
+    const std::string & uri, bool allowRelative)
+{
+    try {
+        return FlakeRef(uri, allowRelative);
+    } catch (BadFlakeRef & e) {
+        return {};
+    }
+}
+
+}