From 95ba078ff672ec372e1926f7ea4bd2c284b952c1 Mon Sep 17 00:00:00 2001
From: Qi Xiao <xiaqqaix@gmail.com>
Date: Sun, 13 Aug 2023 23:11:37 -0400
Subject: [PATCH] pkg/eval/evaltest: Implement value matchers with interface.

---
 .../{matchers.go => error_matchers.go}        | 39 ------------
 pkg/eval/evaltest/evaltest.go                 | 20 ++-----
 pkg/eval/evaltest/value_matchers.go           | 59 +++++++++++++++++++
 3 files changed, 64 insertions(+), 54 deletions(-)
 rename pkg/eval/evaltest/{matchers.go => error_matchers.go} (75%)
 create mode 100644 pkg/eval/evaltest/value_matchers.go

diff --git a/pkg/eval/evaltest/matchers.go b/pkg/eval/evaltest/error_matchers.go
similarity index 75%
rename from pkg/eval/evaltest/matchers.go
rename to pkg/eval/evaltest/error_matchers.go
index 57eb69fbc..2a6d64a11 100644
--- a/pkg/eval/evaltest/matchers.go
+++ b/pkg/eval/evaltest/error_matchers.go
@@ -2,51 +2,12 @@ package evaltest
 
 import (
 	"fmt"
-	"math"
 	"reflect"
-	"regexp"
 
 	"src.elv.sh/pkg/eval"
 	"src.elv.sh/pkg/parse"
 )
 
-// Anything is a value that can be passed to [Case.Puts] to match any value. It
-// is useful when the value contains information that is useful when the test
-// fails.
-var Anything = anything{}
-
-type anything struct{}
-
-// ApproximatelyThreshold defines the threshold for matching float64 values when
-// using Approximately.
-const ApproximatelyThreshold = 1e-15
-
-// Approximately returns a value that can be passed to Case.Puts to match a
-// float64 within the threshold defined by ApproximatelyThreshold.
-func Approximately(f float64) any { return approximately{f} }
-
-type approximately struct{ value float64 }
-
-func matchFloat64(a, b, threshold float64) bool {
-	if math.IsNaN(a) && math.IsNaN(b) {
-		return true
-	}
-	if math.IsInf(a, 0) && math.IsInf(b, 0) &&
-		math.Signbit(a) == math.Signbit(b) {
-		return true
-	}
-	return math.Abs(a-b) <= threshold
-}
-
-// StringMatching returns a value that can be passed to Case.Puts to match any
-// string matching a regexp pattern. If the pattern is not a valid regexp, the
-// function panics.
-func StringMatching(p string) any {
-	return stringMatching{regexp.MustCompile(p)}
-}
-
-type stringMatching struct{ pattern *regexp.Regexp }
-
 type errorMatcher interface{ matchError(error) bool }
 
 // An errorMatcher for compilation errors.
diff --git a/pkg/eval/evaltest/evaltest.go b/pkg/eval/evaltest/evaltest.go
index fe58c9b68..9a45accc6 100644
--- a/pkg/eval/evaltest/evaltest.go
+++ b/pkg/eval/evaltest/evaltest.go
@@ -259,23 +259,13 @@ func matchOut(want, got []any) bool {
 }
 
 func match(got, want any) bool {
-	if want == Anything {
-		return true
+	if matcher, ok := want.(ValueMatcher); ok {
+		return matcher.matchValue(got)
 	}
-	switch got := got.(type) {
-	case float64:
-		// Special-case float64 to correctly handle NaN and support
-		// approximate comparison.
-		switch want := want.(type) {
-		case float64:
+	// Special-case float64 to handle NaNs and infinities.
+	if got, ok := got.(float64); ok {
+		if want, ok := want.(float64); ok {
 			return matchFloat64(got, want, 0)
-		case approximately:
-			return matchFloat64(got, want.value, ApproximatelyThreshold)
-		}
-	case string:
-		switch want := want.(type) {
-		case stringMatching:
-			return want.pattern.MatchString(got)
 		}
 	}
 	return vals.Equal(got, want)
diff --git a/pkg/eval/evaltest/value_matchers.go b/pkg/eval/evaltest/value_matchers.go
new file mode 100644
index 000000000..c9ccb8267
--- /dev/null
+++ b/pkg/eval/evaltest/value_matchers.go
@@ -0,0 +1,59 @@
+package evaltest
+
+import (
+	"math"
+	"regexp"
+)
+
+// ValueMatcher is a value that can be passed to [Case.Puts] and has its own
+// matching semantics.
+type ValueMatcher interface{ matchValue(any) bool }
+
+// Anything matches anything. It is useful when the value contains information
+// that is useful when the test fails.
+var Anything ValueMatcher = anything{}
+
+type anything struct{}
+
+func (anything) matchValue(any) bool { return true }
+
+// ApproximatelyThreshold defines the threshold for matching float64 values when
+// using [Approximately].
+const ApproximatelyThreshold = 1e-15
+
+// Approximately matches a float64 within the threshold defined by
+// [ApproximatelyThreshold].
+func Approximately(f float64) ValueMatcher { return approximately{f} }
+
+type approximately struct{ value float64 }
+
+func (a approximately) matchValue(value any) bool {
+	if value, ok := value.(float64); ok {
+		return matchFloat64(a.value, value, ApproximatelyThreshold)
+	}
+	return false
+}
+
+func matchFloat64(a, b, threshold float64) bool {
+	if math.IsNaN(a) && math.IsNaN(b) {
+		return true
+	}
+	if math.IsInf(a, 0) && math.IsInf(b, 0) &&
+		math.Signbit(a) == math.Signbit(b) {
+		return true
+	}
+	return math.Abs(a-b) <= threshold
+}
+
+// [StringMatching] matches any string matching a regexp pattern. If the pattern
+// is not a valid regexp, the function panics.
+func StringMatching(p string) ValueMatcher { return stringMatching{regexp.MustCompile(p)} }
+
+type stringMatching struct{ pattern *regexp.Regexp }
+
+func (s stringMatching) matchValue(value any) bool {
+	if value, ok := value.(string); ok {
+		return s.pattern.MatchString(value)
+	}
+	return false
+}