feat: match dashboard cost formatting and guardrail messages (#4)

* feat: match dashboard cost formatting and guardrail messages

Update formatCost to use the dashboard's autoDecimals behavior: values
>= $1 are rounded to whole numbers, values < $1 show 2 decimal places.

Rewrite formatGuardrailMessage to match the dashboard's
buildTriggerReason, including scope, threshold explanations, and user
message. This requires the new config fields added to GuardrailResult
in go-proto.

* update go.mod

Author: liamcervante

go.mod

@@ -4,7 +4,7 @@ go 1.25.5
 
 require (
 	github.com/google/go-cmp v0.7.0
-	github.com/infracost/go-proto v0.11.0
+	github.com/infracost/go-proto v0.12.0
 	github.com/infracost/proto v1.29.0
 	github.com/shurcooL/githubv4 v0.0.0-20260209031235-2402fdf4a9ed
 	golang.org/x/oauth2 v0.36.0

go.sum

@@ -24,8 +24,8 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/hashicorp/hcl/v2 v2.24.0 h1:2QJdZ454DSsYGoaE6QheQZjtKZSUs9Nh2izTWiwQxvE=
 github.com/hashicorp/hcl/v2 v2.24.0/go.mod h1:oGoO1FIQYfn/AgyOhlg9qLC6/nOJPX3qGbkZpYAcqfM=
-github.com/infracost/go-proto v0.11.0 h1:Q6nRZDxLJUsdVI0JDgnAb8NL/2JvhmgklZ2aYIeQmtI=
-github.com/infracost/go-proto v0.11.0/go.mod h1:VtzyuTe3h6GzrgHOQkVxjiP6Wpn4iUbr1HDaszcaV3k=
+github.com/infracost/go-proto v0.12.0 h1:A+4/yEkqp0IWiCgOcgF4Auw1l92LWGUzd8sZhGXWeDA=
+github.com/infracost/go-proto v0.12.0/go.mod h1:VtzyuTe3h6GzrgHOQkVxjiP6Wpn4iUbr1HDaszcaV3k=
 github.com/infracost/proto v1.29.0 h1:+SaqDjOwGMpKlitplVS9GdK3TnL4kat0Iyfbxkvzudk=
 github.com/infracost/proto v1.29.0/go.mod h1:Z8vPWBWblwJlw+/ksO+BtsXwf9NiOcSTWx0WRWNbfUA=
 github.com/mitchellh/go-wordwrap v1.0.1 h1:TLuKupo69TCn6TQSyGxwI1EblZZEsQ0vMlAFQflz0v0=

pkg/vcs/comment/costs.go

@@ -202,10 +202,16 @@ func formatPercentChange(oldCost, newCost *rat.Rat) string {
 	return fmt.Sprintf("%s%s%%", percentSym, p.StringFixed(0))
 }
 
-// formatCost formats a cost value with currency symbol.
+// formatCost formats a cost value with currency symbol, matching the
+// dashboard's autoDecimals behavior: values with absolute value >= 1 (or zero)
+// are rounded to whole numbers, smaller values show 2 decimal places.
+// See: dashboard/api/src/utils/format.ts CurrencyFormatter.formatCost
 func formatCost(d *rat.Rat, currency string) string {
-	if d == nil {
-		return currencySymbol(currency) + "0.00"
+	if d == nil || d.IsZero() {
+		return currencySymbol(currency) + "0"
+	}
+	if d.Abs().GreaterThanOrEqual(rat.New(1)) {
+		return currencySymbol(currency) + d.StringFixed(0)
 	}
 	return currencySymbol(currency) + d.StringFixed(2)
 }

pkg/vcs/comment/governance.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/infracost/go-proto/pkg/event"
 	"github.com/infracost/go-proto/pkg/rat"
+	protoevent "github.com/infracost/proto/gen/go/infracost/parser/event"
 	"github.com/infracost/proto/gen/go/infracost/provider"
 )
 
@@ -234,7 +235,7 @@ func (data *Data) processGuardrailResults(inputs *Inputs) {
 		entry := GovernanceEntry{
 			Title:    title,
 			Blocking: result.BlockPR,
-			Message:  formatGuardrailMessage(result),
+			Message:  formatGuardrailMessage(result, data.Currency),
 		}
 
 		table.Entries = append(table.Entries, entry)
@@ -438,19 +439,57 @@ func formatTagIssues(resource event.TagPolicyResultResource) []string {
 	return issues
 }
 
-// formatGuardrailMessage builds the trigger description for a guardrail result.
-func formatGuardrailMessage(result event.GuardrailResult) string {
+// formatGuardrailMessage builds the trigger description for a guardrail result,
+// matching the dashboard's buildTriggerReason logic.
+// See: dashboard/api/src/services/guardrails.ts buildTriggerReason (~line 1008)
+func formatGuardrailMessage(result event.GuardrailResult, currency string) string {
 	var parts []string
 
-	if result.Increase != nil && result.Increase.GreaterThanZero() {
-		parts = append(parts, fmt.Sprintf("Cost increase: %s/mo", result.Increase.StringFixed(2)))
+	if result.Scope == protoevent.Guardrail_PROJECT {
+		parts = append(parts, "At least one project exceeded per-project threshold.")
 	}
-	if result.PercentIncrease != nil && result.PercentIncrease.GreaterThanZero() {
-		parts = append(parts, fmt.Sprintf("(%s%%)", result.PercentIncrease.StringFixed(0)))
+
+	hasIncrease := result.IncreaseThreshold != nil
+	hasPercent := result.IncreasePercentThreshold != nil
+
+	if hasIncrease {
+		cost := formatCost(result.Increase, currency)
+		if hasPercent {
+			parts = append(parts, fmt.Sprintf(
+				"Cost increased by %s (%s%%), threshold was %s and %s%%.",
+				cost,
+				result.PercentIncrease.StringFixed(0),
+				formatCost(result.IncreaseThreshold, currency),
+				result.IncreasePercentThreshold.StringFixed(0),
+			))
+		} else {
+			parts = append(parts, fmt.Sprintf(
+				"Cost increased by %s, threshold was %s.",
+				cost,
+				formatCost(result.IncreaseThreshold, currency),
+			))
+		}
+	} else if hasPercent {
+		if result.PercentIncrease != nil && !result.PercentIncrease.IsZero() {
+			parts = append(parts, fmt.Sprintf(
+				"Cost increased by %s (%s%%), threshold was %s%%.",
+				formatCost(result.Increase, currency),
+				result.PercentIncrease.StringFixed(0),
+				result.IncreasePercentThreshold.StringFixed(0),
+			))
+		}
+	}
+
+	if result.TotalThreshold != nil {
+		parts = append(parts, fmt.Sprintf(
+			"New monthly cost was %s, threshold was %s.",
+			formatCost(result.TotalMonthlyCost, currency),
+			formatCost(result.TotalThreshold, currency),
+		))
 	}
 
-	if len(result.TriggeringProjectNames) > 0 {
-		parts = append(parts, fmt.Sprintf("in %s", formatProjectNamesLabel(result.TriggeringProjectNames)))
+	if result.Message != "" {
+		parts = append(parts, result.Message)
 	}
 
 	return strings.Join(parts, " ")

pkg/vcs/comment/template.go

@@ -146,16 +146,16 @@ func formatCostChangeSentence(data *Data) string {
 	currency := data.Currency
 
 	if past == nil {
-		return fmt.Sprintf("Monthly estimate increased by %s%s 📈",
-			currencySymbol(currency), total.StringFixed(2))
+		return fmt.Sprintf("Monthly estimate increased by %s 📈",
+			formatCost(total, currency))
 	}
 
 	if past.Equals(total) {
 		return "Monthly estimate generated"
 	}
 
 	diff := total.Sub(past).Abs()
-	change := currencySymbol(currency) + diff.StringFixed(2)
+	change := formatCost(diff, currency)
 
 	if past.GreaterThan(total) {
 		return fmt.Sprintf("Monthly estimate decreased by %s 📉", change)

pkg/vcs/comment/template_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/infracost/go-proto/pkg/event"
 	"github.com/infracost/go-proto/pkg/rat"
 	parserpb "github.com/infracost/proto/gen/go/infracost/parser"
+	protoevent "github.com/infracost/proto/gen/go/infracost/parser/event"
 	"github.com/infracost/proto/gen/go/infracost/provider"
 )
 
@@ -304,6 +305,8 @@ func TestRender(t *testing.T) {
 						Increase:               rat.New(400),
 						PercentIncrease:        rat.New(400),
 						TriggeringProjectNames: []string{"my-project"},
+						Scope:                  protoevent.Guardrail_PROJECT,
+						IncreaseThreshold:      rat.New(100),
 					},
 				},
 				Projects: []ProjectResult{

pkg/vcs/comment/testdata/cost_increase.md

@@ -1,7 +1,7 @@
 <h3>💰 Infracost report</h3>
 This pull request is aligned with your company's FinOps policies and the Well-Architected Framework.
 <details >
-  <summary><b>Monthly estimate increased by $50.00 📈</b> </summary>
+  <summary><b>Monthly estimate increased by $50 📈</b> </summary>
   <br/>
 
 <table>
@@ -15,10 +15,10 @@ This pull request is aligned with your company's FinOps policies and the Well-Ar
   <tbody>
     <tr>
       <td>my-project</td>
-      <td align="right">+$45.00</td>
-      <td align="right">+$5.00</td>
-      <td align="right">+$50.00 (+25%)</td>
-      <td align="right">$250.00</td>
+      <td align="right">+$45</td>
+      <td align="right">+$5</td>
+      <td align="right">+$50 (+25%)</td>
+      <td align="right">$250</td>
     </tr>
   </tbody>
 </table>
@@ -35,13 +35,13 @@ Key: * usage cost, ~ changed, + added, - removed
 Project: my-project
 
 ~ aws_instance.web
-  +$50.00 ($200.00 → $250.00)
+  +$50 ($200 → $250)
 
     ~ Linux/UNIX usage (on-demand, m5.xlarge)
-      +$50.00 ($70.00 → $140.00)
+      +$50 ($70 → $140)
 
 Monthly cost change for my-project
-Amount:  +$50.00 ($200.00 → $250.00)
+Amount:  +$50 ($200 → $250)
 Percent: +25%
 
 ──────────────────────────────────

pkg/vcs/comment/testdata/environmental_metrics.md

@@ -23,7 +23,7 @@ Graviton instances are more energy efficient.
 
   </table>
 <details >
-  <summary><b>Monthly estimate increased by $100.00 📈</b> (🌱 emit 500.0 kg CO₂e - that's more than 3.3 flights between London & Paris)</summary>
+  <summary><b>Monthly estimate increased by $100 📈</b> (🌱 emit 500.0 kg CO₂e - that's more than 3.3 flights between London & Paris)</summary>
   <br/>
 
 <table>
@@ -37,10 +37,10 @@ Graviton instances are more energy efficient.
   <tbody>
     <tr>
       <td>my-project</td>
-      <td align="right">+$100.00</td>
+      <td align="right">+$100</td>
       <td align="right">-</td>
-      <td align="right">+$100.00 (+50%)</td>
-      <td align="right">$300.00</td>
+      <td align="right">+$100 (+50%)</td>
+      <td align="right">$300</td>
     </tr>
   </tbody>
 </table>
@@ -59,10 +59,10 @@ Key: * usage cost, ~ changed, + added, - removed
 Project: my-project
 
 ~ aws_instance.web
-  +$100.00 ($200.00 → $300.00)
+  +$100 ($200 → $300)
 
 Monthly cost change for my-project
-Amount:  +$100.00 ($200.00 → $300.00)
+Amount:  +$100 ($200 → $300)
 Percent: +50%
 
 ──────────────────────────────────

pkg/vcs/comment/testdata/guardrail_blocks.md

@@ -10,12 +10,12 @@
 </td></tr>
 <tr><td></td><td>
 
-Cost increase: 400.00/mo (400%) in project `my-project`
+At least one project exceeded per-project threshold. Cost increased by $400, threshold was $100.
 </td></tr>
 
   </table>
 <details open>
-  <summary><b>Monthly estimate increased by $400.00 📈</b> </summary>
+  <summary><b>Monthly estimate increased by $400 📈</b> </summary>
   <br/>
 
 <table>
@@ -29,10 +29,10 @@ Cost increase: 400.00/mo (400%) in project `my-project`
   <tbody>
     <tr>
       <td>my-project</td>
-      <td align="right">+$400.00</td>
+      <td align="right">+$400</td>
       <td align="right">-</td>
-      <td align="right">+$400.00 (+400%)</td>
-      <td align="right">$500.00</td>
+      <td align="right">+$400 (+400%)</td>
+      <td align="right">$500</td>
     </tr>
   </tbody>
 </table>
@@ -49,10 +49,10 @@ Key: * usage cost, ~ changed, + added, - removed
 Project: my-project
 
 ~ aws_instance.big
-  +$400.00 ($100.00 → $500.00)
+  +$400 ($100 → $500)
 
 Monthly cost change for my-project
-Amount:  +$400.00 ($100.00 → $500.00)
+Amount:  +$400 ($100 → $500)
 Percent: +400%
 
 ──────────────────────────────────

pkg/vcs/comment/testdata/project_errors.md

@@ -12,7 +12,7 @@
 <hr/>
 This pull request is aligned with your company's FinOps policies and the Well-Architected Framework.
 <details >
-  <summary><b>Monthly estimate increased by $0.00 📈</b> </summary>
+  <summary><b>Monthly estimate increased by $0 📈</b> </summary>
   <br/>
   <details>
   <summary>Estimate details (includes details of skipped projects due to errors)</summary>