Parse assumes syntax

assumes/expression.go

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+// Copyright 2021 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package assumes
+
+import "github.com/juju/version/v2"
+
+var (
+	_ Expression = (*FeatureExpression)(nil)
+	_ Expression = (*CompositeExpression)(nil)
+)
+
+// ExpressionType represents the type of an assumes expression.
+type ExpressionType string
+
+const (
+	AnyOfExpression ExpressionType = "any-of"
+	AllOfExpression ExpressionType = "all-of"
+)
+
+// Expression is an interface implemented by all expression types in this package.
+type Expression interface {
+	Type() ExpressionType
+}
+
+// VersionConstraint describes a constraint for required feature versions.
+type VersionConstraint string
+
+const (
+	VersionGTE VersionConstraint = ">="
+	VersionLT  VersionConstraint = "<"
+)
+
+// FeatureExpression describes a feature that is required by the charm in order
+// to be successfully deployed. Feature expressions may additionally specify a
+// version constraint.
+type FeatureExpression struct {
+	// The name of the feature.
+	Name string
+
+	// A feature within an assumes block may optionally specify a version
+	// constraint.
+	Constraint VersionConstraint
+	Version    *version.Number
+
+	// The raw, unprocessed version string for serialization purposes.
+	rawVersion string
+}
+
+// Type implements Expression.
+func (FeatureExpression) Type() ExpressionType { return ExpressionType("feature") }
+
+// CompositeExpression describes a composite expression that applies some
+// operator to a sub-expression list.
+type CompositeExpression struct {
+	ExprType       ExpressionType
+	SubExpressions []Expression
+}
+
+// Type implements Expression.
+func (expr CompositeExpression) Type() ExpressionType { return expr.ExprType }

assumes/package_test.go

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+// Copyright 2021 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package assumes
+
+import (
+	stdtesting "testing"
+
+	gc "gopkg.in/check.v1"
+)
+
+func Test(t *stdtesting.T) {
+	gc.TestingT(t)
+}