Deprecate ${name} in favour of {{name}} (multi-phase migration)

[thomas-stegemann]

Why

After #125 v1 landed, Bowire has two interpolation syntaxes that resolve identically:

• ${name} — Bowire's original Bash-style syntax (escape: $${name})
• {{name}} — Postman / Mustache convention (escape: {{{{name}}}})

Two syntaxes for one operation is confusing — every doc reader, new operator, and recording author has to learn both. {{...}} won the design call because:

• It matches Postman / Insomnia / Hoppscotch — every importer hits it for free
• It composes cleanly with source prefixes ({{env.X}}, {{prev.X}}, {{step1.Y}})
• Phase-2 features (autocomplete dropdown, color-coded chips, source picker) target it

${...} stays as a legacy alias only because every existing recording / collection / saved request uses it. We need a planned migration window before deprecation.

Plan

Phase 0 — Today

• Both syntaxes work. Documentation + new examples should already prefer {{...}}.

Phase 1 — Soft deprecation

• Add a one-time toast on workbench load when the active workspace's stored data contains ${...} placeholders: "This workspace uses the legacy ${name} syntax. The canonical syntax is {{name}}. Open Settings → Migration to convert."
• New surfaces (Cmd+K palette, AI prompts, empty-state copy) only emit {{...}}.
• Docs explicitly mark ${...} as legacy.

Phase 2 — Migration tool

• Settings → Migration page or one-shot migration command.
• Walks every recording, collection, environment, flow, freeform draft — rewrites ${name} to {{name}} (and ${response.X} to {{prev.X}}, ${now} to {{runtime.now}}, etc.).
• Dry-run + diff view before commit. Per-workspace scope.
• Disk-stored recordings get touched too.
• Migration emits a single commit-style transition record so the workspace metadata says "migrated to {{}}-syntax at ".

Phase 3 — Hard deprecation

• ${name} substitution stops resolving. Placeholders pass through literally (so the operator sees the typo).
• One-line warning in the workbench console: "Legacy ${} interpolation is no longer resolved. Run Settings → Migration to convert."
• Major-version bump.

Phase 4 — Removal

• Parser drops the ${...} branch entirely. Next major version after Phase 3.

Migration script — concrete rewrites

From	To
${NAME}	{{NAME}}
${env.NAME}	{{env.NAME}}
${response.path}	{{prev.path}}
${response}	{{prev}}
${now} / ${nowMs} / ${timestamp}	{{runtime.now}} / {{runtime.nowMs}} / {{runtime.timestamp}}
${uuid} / ${random}	{{runtime.uuid}} / {{runtime.random}}
${now+3600}	{{runtime.now+3600}}
$${NAME} (literal escape)	{{{{NAME}}}} (quadruple-brace escape)

The migration walks string-typed fields in:

• recordingsList[].steps[].body / messages[] / metadata
• collectionsList[].items[].body / headers / params
• getEnvironments()[].vars[].value
• flowsList[].nodes[].config.<various>
• freeformRequest.body / serverUrl / metadata

Acceptance — per phase

Phase 1

• Toast on workspace load when ${...} placeholders detected.
• All shipped examples / docs / new-tab defaults use {{...}}.
• Empty-state hints (Layout cleanup — top bar, sidebar, main pane, drawers (left-sidebar model stays) #129) emit {{...}} examples only.

Phase 2

• Settings → Migration page with dry-run preview.
• One-command migration via Bowire.Cli migrate-vars (for embedded / headless).
• Per-workspace migration log persisted.
• Migration is idempotent (re-running yields no diff).

Phase 3

• ${...} no longer substitutes; renders literally.
• Console warning on load when ${...} still present.
• Release note documents the breaking change.

Phase 4

• Parser branch removed.
• One major version after Phase 3 ships.

Composes with

• Workspaces — named, switchable contexts that bundle URLs / envs / collections / AI config #116 Workspaces — migration scopes per workspace.
• Auto-save to workspace + live save-state pill #127 Save-pill — migration emits "Saved to " once converted.
• Uniform delete affordances on every list sidebar (single / multi-select / all) #143 Trash — pre-migration originals land in trash so a missed surprise can be recovered.

Out of scope

• Auto-migration on first read of a recording. Too magical; operator must opt in via the migration tool.
• Re-encoding ${...} to \\{...\\} or other escape forms. The canonical move is the syntactic swap, not a hybrid.