Add behavioral tests for examples from the YAML spec (databricks#1835)

## Changes

I took the examples from https://yaml.org/spec/1.2.2.

The required modifications to the loader are:
* Correctly parse floating point infinities and NaN
* Correctly parse octal numbers per the YAML 1.2 spec
* Treat "null" keys in a map as valid

## Tests

Existing and new unit tests pass.

libs/dyn/dynassert/dump.go

@@ -0,0 +1,60 @@
+package dynassert
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/databricks/cli/libs/dyn"
+)
+
+// Dump returns the Go code to recreate the given value.
+func Dump(v dyn.Value) string {
+	var sb strings.Builder
+	dump(v, &sb)
+	return sb.String()
+}
+
+func dump(v dyn.Value, sb *strings.Builder) {
+	sb.WriteString("dyn.NewValue(\n")
+
+	switch v.Kind() {
+	case dyn.KindMap:
+		sb.WriteString("map[string]dyn.Value{")
+		m := v.MustMap()
+		for _, p := range m.Pairs() {
+			sb.WriteString(fmt.Sprintf("\n%q: ", p.Key.MustString()))
+			dump(p.Value, sb)
+			sb.WriteByte(',')
+		}
+		sb.WriteString("\n},\n")
+	case dyn.KindSequence:
+		sb.WriteString("[]dyn.Value{\n")
+		for _, e := range v.MustSequence() {
+			dump(e, sb)
+			sb.WriteByte(',')
+		}
+		sb.WriteString("},\n")
+	case dyn.KindString:
+		sb.WriteString(fmt.Sprintf("%q,\n", v.MustString()))
+	case dyn.KindBool:
+		sb.WriteString(fmt.Sprintf("%t,\n", v.MustBool()))
+	case dyn.KindInt:
+		sb.WriteString(fmt.Sprintf("%d,\n", v.MustInt()))
+	case dyn.KindFloat:
+		sb.WriteString(fmt.Sprintf("%f,\n", v.MustFloat()))
+	case dyn.KindTime:
+		sb.WriteString(fmt.Sprintf("dyn.NewTime(%q),\n", v.MustTime().String()))
+	case dyn.KindNil:
+		sb.WriteString("nil,\n")
+	default:
+		panic(fmt.Sprintf("unhandled kind: %v", v.Kind()))
+	}
+
+	// Add location
+	sb.WriteString("[]dyn.Location{")
+	for _, l := range v.Locations() {
+		sb.WriteString(fmt.Sprintf("{File: %q, Line: %d, Column: %d},", l.File, l.Line, l.Column))
+	}
+	sb.WriteString("},\n")
+	sb.WriteString(")")
+}

libs/dyn/yamlloader/loader.go

@@ -105,6 +105,9 @@ func (d *loader) loadMapping(node *yaml.Node, loc dyn.Location) (dyn.Value, erro
 		switch st {
 		case "!!str":
 			// OK
+		case "!!null":
+			// A literal unquoted "null" is treated as a null value by the YAML parser.
+			// However, when used as a key, it is treated as the string "null".
 		case "!!merge":
 			if merge != nil {
 				panic("merge node already set")
@@ -115,10 +118,11 @@ func (d *loader) loadMapping(node *yaml.Node, loc dyn.Location) (dyn.Value, erro
 			return dyn.InvalidValue, errorf(loc, "invalid key tag: %v", st)
 		}
 
-		k, err := d.load(key)
-		if err != nil {
-			return dyn.InvalidValue, err
-		}
+		k := dyn.NewValue(key.Value, []dyn.Location{{
+			File:   d.path,
+			Line:   key.Line,
+			Column: key.Column,
+		}})
 
 		v, err := d.load(val)
 		if err != nil {
@@ -173,6 +177,14 @@ func (d *loader) loadMapping(node *yaml.Node, loc dyn.Location) (dyn.Value, erro
 	return dyn.NewValue(out, []dyn.Location{loc}), nil
 }
 
+func newIntValue(i64 int64, loc dyn.Location) dyn.Value {
+	// Use regular int type instead of int64 if possible.
+	if i64 >= math.MinInt32 && i64 <= math.MaxInt32 {
+		return dyn.NewValue(int(i64), []dyn.Location{loc})
+	}
+	return dyn.NewValue(i64, []dyn.Location{loc})
+}
+
 func (d *loader) loadScalar(node *yaml.Node, loc dyn.Location) (dyn.Value, error) {
 	st := node.ShortTag()
 	switch st {
@@ -188,18 +200,44 @@ func (d *loader) loadScalar(node *yaml.Node, loc dyn.Location) (dyn.Value, error
 			return dyn.InvalidValue, errorf(loc, "invalid bool value: %v", node.Value)
 		}
 	case "!!int":
-		i64, err := strconv.ParseInt(node.Value, 10, 64)
-		if err != nil {
-			return dyn.InvalidValue, errorf(loc, "invalid int value: %v", node.Value)
+		// Try to parse the an integer value in base 10.
+		// We trim leading zeros to avoid octal parsing of the "0" prefix.
+		// See "testdata/spec_example_2.19.yml" for background.
+		i64, err := strconv.ParseInt(strings.TrimLeft(node.Value, "0"), 10, 64)
+		if err == nil {
+			return newIntValue(i64, loc), nil
 		}
-		// Use regular int type instead of int64 if possible.
-		if i64 >= math.MinInt32 && i64 <= math.MaxInt32 {
-			return dyn.NewValue(int(i64), []dyn.Location{loc}), nil
+		// Let the [ParseInt] function figure out the base.
+		i64, err = strconv.ParseInt(node.Value, 0, 64)
+		if err == nil {
+			return newIntValue(i64, loc), nil
 		}
-		return dyn.NewValue(i64, []dyn.Location{loc}), nil
+		return dyn.InvalidValue, errorf(loc, "invalid int value: %v", node.Value)
 	case "!!float":
 		f64, err := strconv.ParseFloat(node.Value, 64)
 		if err != nil {
+			// Deal with infinity prefixes.
+			v := strings.ToLower(node.Value)
+			switch {
+			case strings.HasPrefix(v, "+"):
+				v = strings.TrimPrefix(v, "+")
+				f64 = math.Inf(1)
+			case strings.HasPrefix(v, "-"):
+				v = strings.TrimPrefix(v, "-")
+				f64 = math.Inf(-1)
+			default:
+				// No prefix.
+				f64 = math.Inf(1)
+			}
+
+			// Deal with infinity and NaN values.
+			switch v {
+			case ".inf":
+				return dyn.NewValue(f64, []dyn.Location{loc}), nil
+			case ".nan":
+				return dyn.NewValue(math.NaN(), []dyn.Location{loc}), nil
+			}
+
 			return dyn.InvalidValue, errorf(loc, "invalid float value: %v", node.Value)
 		}
 		return dyn.NewValue(f64, []dyn.Location{loc}), nil

libs/dyn/yamlloader/testdata/spec_example_2.1.yml

@@ -0,0 +1,5 @@
+# Example 2.1 Sequence of Scalars (ball players)
+
+- Mark McGwire
+- Sammy Sosa
+- Ken Griffey

libs/dyn/yamlloader/testdata/spec_example_2.10.yml

@@ -0,0 +1,10 @@
+# Example 2.10 Node for “Sammy Sosa” appears twice in this document
+
+---
+hr:
+- Mark McGwire
+# Following node labeled SS
+- &SS Sammy Sosa
+rbi:
+- *SS # Subsequent occurrence
+- Ken Griffey

libs/dyn/yamlloader/testdata/spec_example_2.11.yml

@@ -0,0 +1,10 @@
+# Example 2.11 Mapping between Sequences
+
+? - Detroit Tigers
+  - Chicago cubs
+: - 2001-07-23
+
+? [ New York Yankees,
+    Atlanta Braves ]
+: [ 2001-07-02, 2001-08-12,
+    2001-08-14 ]

libs/dyn/yamlloader/testdata/spec_example_2.12.yml

@@ -0,0 +1,10 @@
+# Example 2.12 Compact Nested Mapping
+
+---
+# Products purchased
+- item    : Super Hoop
+  quantity: 1
+- item    : Basketball
+  quantity: 4
+- item    : Big Shoes
+  quantity: 1

libs/dyn/yamlloader/testdata/spec_example_2.13.yml

@@ -0,0 +1,6 @@
+# Example 2.13 In literals, newlines are preserved
+
+# ASCII Art
+--- |
+  \//||\/||
+  // ||  ||__

libs/dyn/yamlloader/testdata/spec_example_2.14.yml

@@ -0,0 +1,6 @@
+# Example 2.14 In the folded scalars, newlines become spaces
+
+--- >
+  Mark McGwire's
+  year was crippled
+  by a knee injury.

libs/dyn/yamlloader/testdata/spec_example_2.15.yml

@@ -0,0 +1,10 @@
+# Example 2.15 Folded newlines are preserved for “more indented” and blank lines
+
+--- >
+ Sammy Sosa completed another
+ fine season with great stats.
+
+   63 Home Runs
+   0.288 Batting Average
+
+ What a year!

libs/dyn/yamlloader/testdata/spec_example_2.16.yml

@@ -0,0 +1,9 @@
+# Example 2.16 Indentation determines scope
+
+name: Mark McGwire
+accomplishment: >
+  Mark set a major league
+  home run record in 1998.
+stats: |
+  65 Home Runs
+  0.278 Batting Average

libs/dyn/yamlloader/testdata/spec_example_2.17.yml

@@ -0,0 +1,9 @@
+# Example 2.17 Quoted Scalars
+
+unicode: "Sosa did fine.\u263A"
+control: "\b1998\t1999\t2000\n"
+hex esc: "\x0d\x0a is \r\n"
+
+single: '"Howdy!" he cried.'
+quoted: ' # Not a ''comment''.'
+tie-fighter: '|\-*-/|'

libs/dyn/yamlloader/testdata/spec_example_2.18.yml

@@ -0,0 +1,8 @@
+# Example 2.18 Multi-line Flow Scalars
+
+plain:
+  This unquoted scalar
+  spans many lines.
+
+quoted: "So does this
+  quoted scalar.\n"

libs/dyn/yamlloader/testdata/spec_example_2.19.yml

@@ -0,0 +1,15 @@
+# Example 2.19 Integers
+
+canonical: 12345
+decimal: +12345
+octal: 0o14
+hexadecimal: 0xC
+
+# Note: this example is not part of the spec but added for completeness.
+#
+# Octal numbers:
+#   - YAML 1.1: prefix is "0"
+#   - YAML 1.2: prefix is "0o"
+# The "gopkg.in/yaml.v3" package accepts both for backwards compat.
+# We accept only the YAML 1.2 prefix "0o".
+octal11: 012345

libs/dyn/yamlloader/testdata/spec_example_2.2.yml

@@ -0,0 +1,5 @@
+# Example 2.2 Mapping Scalars to Scalars (player statistics)
+
+hr:  65    # Home runs
+avg: 0.278 # Batting average
+rbi: 147   # Runs Batted In

libs/dyn/yamlloader/testdata/spec_example_2.20.yml

@@ -0,0 +1,7 @@
+# Example 2.20 Floating Point
+
+canonical: 1.23015e+3
+exponential: 12.3015e+02
+fixed: 1230.15
+negative infinity: -.inf
+not a number: .nan

libs/dyn/yamlloader/testdata/spec_example_2.21.yml

@@ -0,0 +1,5 @@
+# Example 2.21 Miscellaneous
+
+null:
+booleans: [ true, false ]
+string: '012345'

libs/dyn/yamlloader/testdata/spec_example_2.22.yml

@@ -0,0 +1,6 @@
+# Example 2.22 Timestamps
+
+canonical: 2001-12-15T02:59:43.1Z
+iso8601: 2001-12-14t21:59:43.10-05:00
+spaced: 2001-12-14 21:59:43.10 -5
+date: 2002-12-14

libs/dyn/yamlloader/testdata/spec_example_2.23.yml

@@ -0,0 +1,15 @@
+# Example 2.23 Various Explicit Tags
+
+---
+not-date: !!str 2002-04-28
+
+picture: !!binary |
+ R0lGODlhDAAMAIQAAP//9/X
+ 17unp5WZmZgAAAOfn515eXv
+ Pz7Y6OjuDg4J+fn5OTk6enp
+ 56enmleECcgggoBADs=
+
+application specific tag: !something |
+ The semantics of the tag
+ above may be different for
+ different documents.

libs/dyn/yamlloader/testdata/spec_example_2.24.yml

@@ -0,0 +1,16 @@
+# Example 2.24 Global Tags
+
+%TAG ! tag:clarkevans.com,2002:
+--- !shape
+  # Use the ! handle for presenting
+  # tag:clarkevans.com,2002:circle
+- !circle
+  center: &ORIGIN {x: 73, y: 129}
+  radius: 7
+- !line
+  start: *ORIGIN
+  finish: { x: 89, y: 102 }
+- !label
+  start: *ORIGIN
+  color: 0xFFEEBB
+  text: Pretty vector drawing.

libs/dyn/yamlloader/testdata/spec_example_2.25.yml

@@ -0,0 +1,9 @@
+# Example 2.25 Unordered Sets
+
+# Sets are represented as a
+# Mapping where each key is
+# associated with a null value
+--- !!set
+? Mark McGwire
+? Sammy Sosa
+? Ken Griffey

libs/dyn/yamlloader/testdata/spec_example_2.26.yml

@@ -0,0 +1,9 @@
+# Example 2.26 Ordered Mappings
+
+# Ordered maps are represented as
+# A sequence of mappings, with
+# each mapping having one key
+--- !!omap
+- Mark McGwire: 65
+- Sammy Sosa: 63
+- Ken Griffey: 58

libs/dyn/yamlloader/testdata/spec_example_2.27.yml

@@ -0,0 +1,31 @@
+# Example 2.27 Invoice
+
+--- !<tag:clarkevans.com,2002:invoice>
+invoice: 34843
+date   : 2001-01-23
+bill-to: &id001
+  given  : Chris
+  family : Dumars
+  address:
+    lines: |
+      458 Walkman Dr.
+      Suite #292
+    city    : Royal Oak
+    state   : MI
+    postal  : 48046
+ship-to: *id001
+product:
+- sku         : BL394D
+  quantity    : 4
+  description : Basketball
+  price       : 450.00
+- sku         : BL4438H
+  quantity    : 1
+  description : Super Hoop
+  price       : 2392.00
+tax  : 251.42
+total: 4443.52
+comments:
+  Late afternoon is best.
+  Backup contact is Nancy
+  Billsmer @ 338-4338.