internal/rosa/python: pip helper

Binary pip releases are not considered acceptable, this more generic helper is required for building from source.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/python.go

@@ -81,6 +81,52 @@ func init() {
 	}
 }
 
+// PipHelper is the [Python] pip packaging helper.
+type PipHelper struct {
+	// Whether to omit --no-build-isolation.
+	BuildIsolation bool
+}
+
+var _ Helper = new(PipHelper)
+
+// extra returns python.
+func (*PipHelper) extra(int) P { return P{Python} }
+
+// wantsChmod returns true.
+func (*PipHelper) wantsChmod() bool { return true }
+
+// wantsWrite is equivalent to wantsChmod.
+func (attr *PipHelper) wantsWrite() bool { return attr.wantsChmod() }
+
+// scriptEarly is a noop.
+func (*PipHelper) scriptEarly() string { return "" }
+
+// createDir returns false.
+func (*PipHelper) createDir() bool { return false }
+
+// wantsDir requests a new directory in TMPDIR.
+func (*PipHelper) wantsDir() string { return `"$(mktemp -d)"` }
+
+// script generates the pip3 install command.
+func (attr *PipHelper) script(name string) string {
+	if attr == nil {
+		attr = new(PipHelper)
+	}
+
+	var extra string
+	if !attr.BuildIsolation {
+		extra += `
+	--no-build-isolation \`
+	}
+
+	return `
+pip3 install \
+	--no-index \
+	--prefix=/system \
+	--root=/work \` + extra + `
+	'/usr/src/` + name + `'`
+}
+
 // newViaPip installs a pip wheel from a url.
 func (t Toolchain) newViaPip(
 	name, version, url, checksum string,