Fix TOML roundtrip: use TomlInline flag instead of FlowStyle to preserve inline tables

FlowStyle affected YAML decode output (causing inline tables to appear as
YAML flow mappings). Replace it with a new TOML-specific TomlInline bool
on CandidateNode that:
- Is set by the TOML decoder for inline tables (not FlowStyle)
- Is copied by UpdateAttributesFrom so it survives DeeplyAssign merges
- Is checked by the TOML encoder alongside FlowStyle (for YAML flow maps)
- Has no effect on the YAML encoder, preserving existing TOML→YAML output

TOML roundtrip tests are restored to their original expected values (inline
tables stay inline, table sections stay as sections).

Agent-Logs-Url: https://github.com/mikefarah/yq/sessions/f59bdf62-6d16-4664-991b-38eb87c9d81c

Co-authored-by: mikefarah <1151925+mikefarah@users.noreply.github.com>

pkg/yqlib/candidate_node.go

@@ -100,6 +100,9 @@ type CandidateNode struct {
 	// For formats like HCL and TOML: indicates that child entries should be emitted as separate blocks/tables
 	// rather than consolidated into nested mappings (default behaviour)
 	EncodeSeparate bool
+	// For TOML: indicates that this mapping was originally a TOML inline table and should be
+	// re-encoded as an inline table rather than a separate table section.
+	TomlInline bool
 }
 
 func (n *CandidateNode) CreateChild() *CandidateNode {
@@ -412,6 +415,7 @@ func (n *CandidateNode) doCopy(cloneContent bool) *CandidateNode {
 		IsMapKey:         n.IsMapKey,
 
 		EncodeSeparate: n.EncodeSeparate,
+		TomlInline:     n.TomlInline,
 	}
 
 	if cloneContent {
@@ -467,6 +471,8 @@ func (n *CandidateNode) UpdateAttributesFrom(other *CandidateNode, prefs assignP
 
 	// Preserve EncodeSeparate flag for format-specific encoding hints
 	n.EncodeSeparate = other.EncodeSeparate
+	// Preserve TomlInline flag for TOML inline table round-trips
+	n.TomlInline = other.TomlInline
 
 	// merge will pickup the style of the new thing
 	// when autocreating nodes

pkg/yqlib/decoder_toml.go

@@ -150,10 +150,10 @@ func (dec *tomlDecoder) createInlineTableMap(tomlNode *toml.Node) (*CandidateNod
 	}
 
 	return &CandidateNode{
-		Kind:    MappingNode,
-		Tag:     "!!map",
-		Style:   FlowStyle,
-		Content: content,
+		Kind:       MappingNode,
+		Tag:        "!!map",
+		TomlInline: true,
+		Content:    content,
 	}, nil
 }
 

pkg/yqlib/doc/usage/toml.md

@@ -153,9 +153,7 @@ yq '.' sample.toml
 ```
 will output
 ```yaml
-[name]
-first = "Tom"
-last = "Preston-Werner"
+name = { first = "Tom", last = "Preston-Werner" }
 ```
 
 ## Roundtrip: table section
@@ -374,10 +372,7 @@ dob = 1979-05-27T07:32:00-08:00
 enabled = true
 ports = [8000, 8001, 8002]
 data = [["delta", "phi"], [3.14]]
-
-[database.temp_targets]
-cpu = 79.5
-case = 72.0
+temp_targets = { cpu = 79.5, case = 72.0 }
 
 # [servers] yq can't do this one yet
 [servers.alpha]

pkg/yqlib/encoder_toml.go

@@ -162,10 +162,9 @@ func (te *tomlEncoder) encodeTopLevelEntry(w io.Writer, path []string, node *Can
 		// Regular array attribute
 		return te.writeArrayAttribute(w, path[len(path)-1], node)
 	case MappingNode:
-		// Use inline table syntax only for nodes explicitly marked with flow/inline style
-		// (e.g. TOML inline tables or YAML flow mappings). All other mappings become
-		// readable TOML table sections.
-		if node.Style&FlowStyle != 0 {
+		// Use inline table syntax for nodes explicitly marked as TOML inline tables
+		// or YAML flow mappings. All other mappings become readable TOML table sections.
+		if node.TomlInline || node.Style&FlowStyle != 0 {
 			return te.writeInlineTableAttribute(w, path[len(path)-1], node)
 		}
 		return te.encodeSeparateMapping(w, path, node)
@@ -428,7 +427,7 @@ func (te *tomlEncoder) writeTableHeader(w io.Writer, path []string, m *Candidate
 // It emits the table header for this mapping if it has any content, then processes children.
 func (te *tomlEncoder) encodeSeparateMapping(w io.Writer, path []string, m *CandidateNode) error {
 	// Check if this mapping has any non-mapping, non-array-of-tables children (i.e., attributes).
-	// Flow-style (inline) mapping children also count as attributes since they render as key = { ... }.
+	// TomlInline mapping children also count as attributes since they render as key = { ... }.
 	hasAttrs := false
 	for i := 0; i < len(m.Content); i += 2 {
 		v := m.Content[i+1]
@@ -436,7 +435,7 @@ func (te *tomlEncoder) encodeSeparateMapping(w io.Writer, path []string, m *Cand
 			hasAttrs = true
 			break
 		}
-		if v.Kind == MappingNode && v.Style&FlowStyle != 0 {
+		if v.Kind == MappingNode && (v.TomlInline || v.Style&FlowStyle != 0) {
 			hasAttrs = true
 			break
 		}
@@ -598,13 +597,13 @@ func (te *tomlEncoder) encodeMappingBodyWithPath(w io.Writer, path []string, m *
 		}
 	}
 
-	// Finally, child mappings: flow-style (inline) ones become inline table attributes,
+	// Finally, child mappings: TomlInline or flow-style ones become inline table attributes,
 	// while all others are emitted as separate sub-table sections.
 	for i := 0; i < len(m.Content); i += 2 {
 		k := m.Content[i].Value
 		v := m.Content[i+1]
 		if v.Kind == MappingNode {
-			if v.Style&FlowStyle != 0 {
+			if v.TomlInline || v.Style&FlowStyle != 0 {
 				if err := te.writeInlineTableAttribute(w, k, v); err != nil {
 					return err
 				}

pkg/yqlib/toml_test.go

@@ -182,12 +182,6 @@ var expectedSampleWithHeader = `servers:
 var rtInlineTableAttr = `name = { first = "Tom", last = "Preston-Werner" }
 `
 
-// Inline tables are converted to readable table sections on encode
-var rtInlineTableAttrEncoded = `[name]
-first = "Tom"
-last = "Preston-Werner"
-`
-
 var rtTableSection = `[owner.contact]
 name = "Tom"
 age = 36
@@ -269,33 +263,6 @@ ip = "10.0.0.2"
 role = "backend"
 `
 
-// Inline table temp_targets is expanded to a readable sub-table when re-encoding
-var sampleFromWebEncoded = `# This is a TOML document
-title = "TOML Example"
-
-[owner]
-name = "Tom Preston-Werner"
-dob = 1979-05-27T07:32:00-08:00
-
-[database]
-enabled = true
-ports = [8000, 8001, 8002]
-data = [["delta", "phi"], [3.14]]
-
-[database.temp_targets]
-cpu = 79.5
-case = 72.0
-
-# [servers] yq can't do this one yet
-[servers.alpha]
-ip = "10.0.0.1"
-role = "frontend"
-
-[servers.beta]
-ip = "10.0.0.2"
-role = "backend"
-`
-
 var subArrays = `
 [[array]]
 
@@ -539,7 +506,7 @@ var tomlScenarios = []formatScenario{
 		description:  "Roundtrip: inline table attribute",
 		input:        rtInlineTableAttr,
 		expression:   ".",
-		expected:     rtInlineTableAttrEncoded,
+		expected:     rtInlineTableAttr,
 		scenarioType: "roundtrip",
 	},
 	{
@@ -638,7 +605,7 @@ var tomlScenarios = []formatScenario{
 		description:  "Roundtrip: sample from web",
 		input:        sampleFromWeb,
 		expression:   ".",
-		expected:     sampleFromWebEncoded,
+		expected:     sampleFromWeb,
 		scenarioType: "roundtrip",
 	},
 	{