Add the semver_spec_string function

Project.toml

@@ -3,11 +3,15 @@ uuid = "8be7a408-1a4a-465c-8be3-3898d13eb8a5"
 authors = ["Dilum Aluthge", "contributors"]
 version = "1.0.0-DEV"
 
-[extras]
-Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+[deps]
+Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 
 [compat]
 julia = "1.6"
 
+[extras]
+Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+
 [targets]
-test = ["Test"]
+test = ["Pkg", "Test"]

src/CompatEntryUtilities.jl

@@ -1,5 +1,27 @@
 module CompatEntryUtilities
 
-# Write your package code here.
+import Pkg
 
+export semver_spec_string
+
+function semver_spec_string(spec::Pkg.Versions.VersionSpec)
+    ranges = spec.ranges
+    isempty(ranges) && return "1 - 0"
+    specs = semver_spec_string.(ranges)
+    return join(specs, ", ")
+end
+
+function semver_spec_string(r::Pkg.Versions.VersionRange)
+    m, n = r.lower.n, r.upper.n
+    if (m, n) == (0, 0)
+        return "≥0"
+    elseif m == 0
+        throw(ArgumentError("This version range cannot be represented using SemVer notation"))
+    elseif n == 0
+        return string("≥", join(r.lower.t, "."),)
+    else
+        return string(join(r.lower.t[1:m], "."), " - ", join(r.upper.t[1:n], "."))
+    end
 end
+
+end # module

test/runtests.jl

@@ -1,6 +1,90 @@
 using CompatEntryUtilities
 using Test
 
+import Pkg
+
+function roundtrip_semver_spec_string(str_1::AbstractString)
+    spec_1 = Pkg.Versions.semver_spec(str_1)
+    str_2 = semver_spec_string(spec_1)
+    spec_2 = Pkg.Versions.semver_spec(str_2)
+    str_3 = semver_spec_string(spec_2)
+    spec_3 = Pkg.Versions.semver_spec(str_3)
+    result = (spec_1 == spec_2) && (spec_1 == spec_3) && (spec_2 == spec_3)
+    if !result
+        @error("Roundtrip failed", str_1, str_2, str_3, spec_1, spec_2, spec_3)
+    end
+    return result
+end
+
 @testset "CompatEntryUtilities.jl" begin
-    # Write your tests here.
+    @testset "semver_spec_string" begin
+        @testset begin
+            let
+                lower = Pkg.Versions.VersionBound()
+                upper = Pkg.Versions.VersionBound(1)
+                r = Pkg.Versions.VersionRange(lower, upper)
+                spec = Pkg.Versions.VersionSpec([r])
+                msg = "This version range cannot be represented using SemVer notation"
+                @test_throws ArgumentError(msg) semver_spec_string(spec)
+            end
+        end
+
+        @testset begin
+            bases = ["0.0.3", "0.2.3", "1.2.3", "0.0", "0.2", "1.2", "0", "1"]
+            specifiers = ["", "^", "~", "= ", ">= ", "≥ "]
+            for specifier in specifiers
+                for base in bases
+                    @test roundtrip_semver_spec_string("$(specifier)$(base)")
+                end
+                @test roundtrip_semver_spec_string(join(string.(Ref(specifier), bases), ", "))
+            end
+        end
+
+        @testset begin
+            bases = ["0.0.3", "0.2.3", "1.2.3", "0.2", "1.2", "1"]
+            specifiers = ["< "]
+            for specifier in specifiers
+                for base in bases
+                    @test roundtrip_semver_spec_string("$(specifier)$(base)")
+                end
+                @test roundtrip_semver_spec_string(join(string.(Ref(specifier), bases), ", "))
+            end
+        end
+
+        @testset begin
+            strs = [
+                # ranges
+                "1.2.3 - 4.5.6",
+                "0.2.3 - 4.5.6",
+                "1.2 - 4.5.6",
+                "1 - 4.5.6",
+                "0.2 - 4.5.6",
+                "0.2 - 0.5.6",
+                "1.2.3 - 4.5",
+                "1.2.3 - 4",
+                "1.2 - 4.5",
+                "1.2 - 4",
+                "1 - 4.5",
+                "1 - 4",
+                "0.2.3 - 4.5",
+                "0.2.3 - 4",
+                "0.2 - 4.5",
+                "0.2 - 4",
+                "0.2 - 0.5",
+                "0.2 - 0",
+
+                # multiple ranges
+                "1 - 2.3, 4.5.6 - 7.8.9",
+
+                # other stuff
+                "1 - 0",
+                "2 - 1",
+                ">= 0",
+            ]
+
+            for str in strs
+                @test roundtrip_semver_spec_string(str)
+            end
+        end
+    end
 end